package bundler

import (
	"bytes"
	"crypto/sha1"
	"encoding/base32"
	"encoding/base64"
	"fmt"
	"mime"
	"net/http"
	"sort"
	"strings"
	"sync"
	"syscall"
	"unicode"
	"unicode/utf8"

	"github.com/evanw/esbuild/internal/ast"
	"github.com/evanw/esbuild/internal/cache"
	"github.com/evanw/esbuild/internal/compat"
	"github.com/evanw/esbuild/internal/config"
	"github.com/evanw/esbuild/internal/css_ast"
	"github.com/evanw/esbuild/internal/css_parser"
	"github.com/evanw/esbuild/internal/fs"
	"github.com/evanw/esbuild/internal/js_ast"
	"github.com/evanw/esbuild/internal/js_lexer"
	"github.com/evanw/esbuild/internal/js_parser"
	"github.com/evanw/esbuild/internal/js_printer"
	"github.com/evanw/esbuild/internal/logger"
	"github.com/evanw/esbuild/internal/resolver"
	"github.com/evanw/esbuild/internal/runtime"
	"github.com/evanw/esbuild/internal/sourcemap"
)

type file struct {
	source    logger.Source
	repr      fileRepr
	loader    config.Loader
	sourceMap *sourcemap.SourceMap

	// The minimum number of links in the module graph to get from an entry point
	// to this file
	distanceFromEntryPoint uint32

	// This holds all entry points that can reach this file. It will be used to
	// assign the parts in this file to a chunk.
	entryBits bitSet

	// If "AbsMetadataFile" is present, this will be filled out with information
	// about this file in JSON format. This is a partial JSON file that will be
	// fully assembled later.
	jsonMetadataChunk []byte

	// The path of this entry point relative to the lowest common ancestor
	// directory containing all entry points. Note: this must have OS-independent
	// path separators (i.e. '/' not '\').
	entryPointRelPath string

	// If this file ends up being used in the bundle, these are additional files
	// that must be written to the output directory. It's used by the "file"
	// loader.
	additionalFiles []OutputFile

	isEntryPoint bool

	// If true, this file was listed as not having side effects by a package.json
	// file in one of our containing directories with a "sideEffects" field.
	ignoreIfUnused bool

	// This is optional additional information about "ignoreIfUnused" for errors
	ignoreIfUnusedData *resolver.IgnoreIfUnusedData
}

type fileRepr interface {
	importRecords() *[]ast.ImportRecord
}

type reprJS struct {
	ast  js_ast.AST
	meta fileMeta

	// If present, this is the CSS file that this JavaScript stub corresponds to.
	// A JavaScript stub is automatically generated for a CSS file when it's
	// imported from a JavaScript file.
	cssSourceIndex *uint32
}

func (repr *reprJS) importRecords() *[]ast.ImportRecord {
	return &repr.ast.ImportRecords
}

type reprCSS struct {
	ast css_ast.AST

	// If present, this is the JavaScript stub corresponding to this CSS file.
	// A JavaScript stub is automatically generated for a CSS file when it's
	// imported from a JavaScript file.
	jsSourceIndex *uint32
}

func (repr *reprCSS) importRecords() *[]ast.ImportRecord {
	return &repr.ast.ImportRecords
}

type Bundle struct {
	fs          fs.FS
	res         resolver.Resolver
	files       []file
	entryPoints []uint32
}

type parseArgs struct {
	fs                 fs.FS
	log                logger.Log
	res                resolver.Resolver
	caches             *cache.CacheSet
	keyPath            logger.Path
	prettyPath         string
	sourceIndex        uint32
	importSource       *logger.Source
	ignoreIfUnused     bool
	ignoreIfUnusedData *resolver.IgnoreIfUnusedData
	importPathRange    logger.Range
	options            config.Options
	results            chan parseResult
	inject             chan config.InjectedFile
	skipResolve        bool
}

type parseResult struct {
	file file
	ok   bool

	resolveResults []*resolver.ResolveResult
}

func parseFile(args parseArgs) {
	source := logger.Source{
		Index:          args.sourceIndex,
		KeyPath:        args.keyPath,
		PrettyPath:     args.prettyPath,
		IdentifierName: js_ast.GenerateNonUniqueNameFromPath(args.keyPath.Text),
	}

	var loader config.Loader
	var absResolveDir string
	var pluginName string

	if stdin := args.options.Stdin; stdin != nil {
		// Special-case stdin
		source.Contents = stdin.Contents
		if stdin.SourceFile != "" {
			source.PrettyPath = stdin.SourceFile
		}
		loader = stdin.Loader
		if loader == config.LoaderNone {
			loader = config.LoaderJS
		}
		absResolveDir = args.options.Stdin.AbsResolveDir
	} else {
		result, ok := runOnLoadPlugins(
			args.options.Plugins,
			args.res,
			args.fs,
			&args.caches.FSCache,
			args.log,
			&source,
			args.importSource,
			args.importPathRange,
		)
		if !ok {
			if args.inject != nil {
				args.inject <- config.InjectedFile{
					SourceIndex: source.Index,
				}
			}
			args.results <- parseResult{}
			return
		}
		loader = result.loader
		absResolveDir = result.absResolveDir
		pluginName = result.pluginName
	}

	_, base, ext := js_ast.PlatformIndependentPathDirBaseExt(source.KeyPath.Text)

	// The special "default" loader determines the loader from the file path
	if loader == config.LoaderDefault {
		loader = loaderFromFileExtension(args.options.ExtensionToLoader, base+ext)
	}

	result := parseResult{
		file: file{
			source: source,
			loader: loader,

			// Record information from "sideEffects" in "package.json"
			ignoreIfUnused:     args.ignoreIfUnused,
			ignoreIfUnusedData: args.ignoreIfUnusedData,
		},
	}

	switch loader {
	case config.LoaderJS:
		ast, ok := args.caches.JSCache.Parse(args.log, source, js_parser.OptionsFromConfig(&args.options))
		result.file.repr = &reprJS{ast: ast}
		result.ok = ok

	case config.LoaderJSX:
		args.options.JSX.Parse = true
		ast, ok := args.caches.JSCache.Parse(args.log, source, js_parser.OptionsFromConfig(&args.options))
		result.file.repr = &reprJS{ast: ast}
		result.ok = ok

	case config.LoaderTS:
		args.options.TS.Parse = true
		ast, ok := args.caches.JSCache.Parse(args.log, source, js_parser.OptionsFromConfig(&args.options))
		result.file.repr = &reprJS{ast: ast}
		result.ok = ok

	case config.LoaderTSX:
		args.options.TS.Parse = true
		args.options.JSX.Parse = true
		ast, ok := args.caches.JSCache.Parse(args.log, source, js_parser.OptionsFromConfig(&args.options))
		result.file.repr = &reprJS{ast: ast}
		result.ok = ok

	case config.LoaderCSS:
		ast := args.caches.CSSCache.Parse(args.log, source, css_parser.Options{
			MangleSyntax:           args.options.MangleSyntax,
			UnsupportedCSSFeatures: args.options.UnsupportedCSSFeatures,
		})
		result.file.repr = &reprCSS{ast: ast}
		result.ok = true

	case config.LoaderJSON:
		expr, ok := args.caches.JSONCache.Parse(args.log, source, js_parser.JSONOptions{})
		ast := js_parser.LazyExportAST(args.log, source, js_parser.OptionsFromConfig(&args.options), expr, "")
		result.file.ignoreIfUnused = true
		result.file.repr = &reprJS{ast: ast}
		result.ok = ok

	case config.LoaderText:
		encoded := base64.StdEncoding.EncodeToString([]byte(source.Contents))
		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(source.Contents)}}
		ast := js_parser.LazyExportAST(args.log, source, js_parser.OptionsFromConfig(&args.options), expr, "")
		ast.URLForCSS = "data:text/plain;base64," + encoded
		result.file.ignoreIfUnused = true
		result.file.repr = &reprJS{ast: ast}
		result.ok = true

	case config.LoaderBase64:
		mimeType := guessMimeType(ext, source.Contents)
		encoded := base64.StdEncoding.EncodeToString([]byte(source.Contents))
		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(encoded)}}
		ast := js_parser.LazyExportAST(args.log, source, js_parser.OptionsFromConfig(&args.options), expr, "")
		ast.URLForCSS = "data:" + mimeType + ";base64," + encoded
		result.file.ignoreIfUnused = true
		result.file.repr = &reprJS{ast: ast}
		result.ok = true

	case config.LoaderBinary:
		encoded := base64.StdEncoding.EncodeToString([]byte(source.Contents))
		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(encoded)}}
		ast := js_parser.LazyExportAST(args.log, source, js_parser.OptionsFromConfig(&args.options), expr, "__toBinary")
		ast.URLForCSS = "data:application/octet-stream;base64," + encoded
		result.file.ignoreIfUnused = true
		result.file.repr = &reprJS{ast: ast}
		result.ok = true

	case config.LoaderDataURL:
		mimeType := guessMimeType(ext, source.Contents)
		encoded := base64.StdEncoding.EncodeToString([]byte(source.Contents))
		url := "data:" + mimeType + ";base64," + encoded
		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(url)}}
		ast := js_parser.LazyExportAST(args.log, source, js_parser.OptionsFromConfig(&args.options), expr, "")
		ast.URLForCSS = url
		result.file.ignoreIfUnused = true
		result.file.repr = &reprJS{ast: ast}
		result.ok = true

	case config.LoaderFile:
		// Add a hash to the file name to prevent multiple files with the same name
		// but different contents from colliding
		hash := hashForFileName([]byte(source.Contents))
		additionalFileName := base + "." + hash + ext
		publicPath := args.options.PublicPath + additionalFileName

		// Determine the destination folder
		targetFolder := args.options.AbsOutputDir

		// Export the resulting relative path as a string
		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(publicPath)}}
		ast := js_parser.LazyExportAST(args.log, source, js_parser.OptionsFromConfig(&args.options), expr, "")
		ast.URLForCSS = publicPath
		result.file.ignoreIfUnused = true
		result.file.repr = &reprJS{ast: ast}
		result.ok = true

		// Optionally add metadata about the file
		var jsonMetadataChunk []byte
		if args.options.AbsMetadataFile != "" {
			jsonMetadataChunk = []byte(fmt.Sprintf(
				"{\n      \"inputs\": {},\n      \"bytes\": %d\n    }", len(source.Contents)))
		}

		// Copy the file using an additional file payload to make sure we only copy
		// the file if the module isn't removed due to tree shaking.
		result.file.additionalFiles = []OutputFile{{
			AbsPath:           args.fs.Join(targetFolder, additionalFileName),
			Contents:          []byte(source.Contents),
			jsonMetadataChunk: jsonMetadataChunk,
		}}

	default:
		args.log.AddRangeError(args.importSource, args.importPathRange,
			fmt.Sprintf("File could not be loaded: %s", source.PrettyPath))
	}

	// This must come before we send on the "results" channel to avoid deadlock
	if args.inject != nil {
		var exports []string
		if repr, ok := result.file.repr.(*reprJS); ok {
			exports = make([]string, 0, len(repr.ast.NamedExports))
			for alias := range repr.ast.NamedExports {
				exports = append(exports, alias)
			}
			sort.Strings(exports) // Sort for determinism
		}
		args.inject <- config.InjectedFile{
			Path:        source.PrettyPath,
			SourceIndex: source.Index,
			Exports:     exports,
		}
	}

	// Stop now if parsing failed
	if !result.ok {
		args.results <- result
		return
	}

	// Run the resolver on the parse thread so it's not run on the main thread.
	// That way the main thread isn't blocked if the resolver takes a while.
	if args.options.Mode == config.ModeBundle && !args.skipResolve {
		// Clone the import records because they will be mutated later
		recordsPtr := result.file.repr.importRecords()
		records := append([]ast.ImportRecord{}, *recordsPtr...)
		*recordsPtr = records
		result.resolveResults = make([]*resolver.ResolveResult, len(records))

		if len(records) > 0 {
			resolverCache := make(map[ast.ImportKind]map[string]*resolver.ResolveResult)

			for importRecordIndex := range records {
				// Don't try to resolve imports that are already resolved
				record := &records[importRecordIndex]
				if record.SourceIndex != nil {
					continue
				}

				// Ignore records that the parser has discarded. This is used to remove
				// type-only imports in TypeScript files.
				if record.IsUnused {
					continue
				}

				// Cache the path in case it's imported multiple times in this file
				cache, ok := resolverCache[record.Kind]
				if !ok {
					cache = make(map[string]*resolver.ResolveResult)
					resolverCache[record.Kind] = cache
				}
				if resolveResult, ok := cache[record.Path.Text]; ok {
					result.resolveResults[importRecordIndex] = resolveResult
					continue
				}

				// Run the resolver and log an error if the path couldn't be resolved
				resolveResult, didLogError := runOnResolvePlugins(
					args.options.Plugins,
					args.res,
					args.log,
					args.fs,
					&source,
					record.Range,
					record.Path.Text,
					record.Kind,
					absResolveDir,
				)
				cache[record.Path.Text] = resolveResult

				// All "require.resolve()" imports should be external because we don't
				// want to waste effort traversing into them
				if record.Kind == ast.ImportRequireResolve {
					if !record.IsInsideTryBody && (resolveResult == nil || !resolveResult.IsExternal) {
						args.log.AddRangeWarning(&source, record.Range,
							fmt.Sprintf("%q should be marked as external for use with \"require.resolve\"", record.Path.Text))
					}
					continue
				}

				if resolveResult == nil {
					// Failed imports inside a try/catch are silently turned into
					// external imports instead of causing errors. This matches a common
					// code pattern for conditionally importing a module with a graceful
					// fallback.
					if !didLogError && !record.IsInsideTryBody {
						hint := ""
						if resolver.IsPackagePath(record.Path.Text) {
							hint = " (mark it as external to exclude it from the bundle)"
							if pluginName == "" && !args.fs.IsAbs(record.Path.Text) {
								if query := args.res.ProbeResolvePackageAsRelative(absResolveDir, record.Path.Text, record.Kind); query != nil {
									hint = fmt.Sprintf(" (use %q to import %q)", "./"+record.Path.Text, args.res.PrettyPath(query.PathPair.Primary))
								}
							}
						}
						if args.options.Platform != config.PlatformNode {
							if _, ok := resolver.BuiltInNodeModules[record.Path.Text]; ok {
								hint = " (set platform to \"node\" when building for node)"
							}
						}
						if absResolveDir == "" && pluginName != "" {
							hint = fmt.Sprintf(" (the plugin %q didn't set a resolve directory)", pluginName)
						}
						args.log.AddRangeError(&source, record.Range,
							fmt.Sprintf("Could not resolve %q%s", record.Path.Text, hint))
					}
					continue
				}

				result.resolveResults[importRecordIndex] = resolveResult
			}
		}
	}

	// Attempt to parse the source map if present
	if loader.CanHaveSourceMap() && args.options.SourceMap != config.SourceMapNone {
		if repr, ok := result.file.repr.(*reprJS); ok && repr.ast.SourceMapComment.Text != "" {
			if path, contents := extractSourceMapFromComment(args.log, args.fs, &args.caches.FSCache,
				args.res, &source, repr.ast.SourceMapComment, absResolveDir); contents != nil {
				result.file.sourceMap = js_parser.ParseSourceMap(args.log, logger.Source{
					KeyPath:    path,
					PrettyPath: args.res.PrettyPath(path),
					Contents:   *contents,
				})
			}
		}
	}

	args.results <- result
}

func guessMimeType(extension string, contents string) string {
	mimeType := mime.TypeByExtension(extension)
	if mimeType == "" {
		mimeType = http.DetectContentType([]byte(contents))
	}

	// Turn "text/plain; charset=utf-8" into "text/plain;charset=utf-8"
	return strings.ReplaceAll(mimeType, "; ", ";")
}

func extractSourceMapFromComment(
	log logger.Log,
	fs fs.FS,
	fsCache *cache.FSCache,
	res resolver.Resolver,
	source *logger.Source,
	comment js_ast.Span,
	absResolveDir string,
) (logger.Path, *string) {
	// Data URL
	if strings.HasPrefix(comment.Text, "data:") {
		if strings.HasPrefix(comment.Text, "data:application/json;") {
			// Scan for the base64 part to support URLs like "data:application/json;charset=utf-8;base64,"
			if index := strings.Index(comment.Text, ";base64,"); index != -1 {
				n := int32(index + len(";base64,"))
				encoded := comment.Text[n:]
				decoded, err := base64.StdEncoding.DecodeString(encoded)
				if err != nil {
					r := logger.Range{Loc: logger.Loc{Start: comment.Range.Loc.Start + n}, Len: comment.Range.Len - n}
					log.AddRangeWarning(source, r, "Invalid base64 data in source map")
					return logger.Path{}, nil
				}
				contents := string(decoded)
				return logger.Path{Text: source.PrettyPath + ".sourceMappingURL"}, &contents
			}
		}

		// Anything else is unsupported
		log.AddRangeWarning(source, comment.Range, "Unsupported source map comment")
		return logger.Path{}, nil
	}

	// Relative path in a file with an absolute path
	if absResolveDir != "" {
		absPath := fs.Join(absResolveDir, comment.Text)
		path := logger.Path{Text: absPath, Namespace: "file"}
		contents, err := fsCache.ReadFile(fs, absPath)
		if err != nil {
			if err == syscall.ENOENT {
				// Don't report a warning because this is likely unactionable
				return logger.Path{}, nil
			}
			log.AddRangeError(source, comment.Range, fmt.Sprintf("Cannot read file %q: %s", res.PrettyPath(path), err.Error()))
			return logger.Path{}, nil
		}
		return path, &contents
	}

	// Anything else is unsupported
	log.AddRangeWarning(source, comment.Range, "Unsupported source map comment")
	return logger.Path{}, nil
}

func logPluginMessages(
	res resolver.Resolver,
	log logger.Log,
	name string,
	msgs []logger.Msg,
	thrown error,
	importSource *logger.Source,
	importPathRange logger.Range,
) bool {
	didLogError := false

	// Report errors and warnings generated by the plugin
	for _, msg := range msgs {
		if name != "" {
			msg.Data.Text = fmt.Sprintf("[%s] %s", name, msg.Data.Text)
		}
		if msg.Kind == logger.Error {
			didLogError = true
		}

		// Sanitize the location
		if msg.Data.Location != nil {
			clone := *msg.Data.Location
			if clone.Namespace == "" {
				clone.Namespace = "file"
			}
			if clone.File == "" {
				clone.File = importSource.PrettyPath
			} else {
				clone.File = res.PrettyPath(logger.Path{Text: clone.File, Namespace: clone.Namespace})
			}
			msg.Data.Location = &clone
		} else {
			msg.Data.Location = logger.LocationOrNil(importSource, importPathRange)
		}

		log.AddMsg(msg)
	}

	// Report errors thrown by the plugin itself
	if thrown != nil {
		didLogError = true
		text := thrown.Error()
		if name != "" {
			text = fmt.Sprintf("[%s] %s", name, text)
		}
		log.AddRangeError(importSource, importPathRange, text)
	}

	return didLogError
}

func runOnResolvePlugins(
	plugins []config.Plugin,
	res resolver.Resolver,
	log logger.Log,
	fs fs.FS,
	importSource *logger.Source,
	importPathRange logger.Range,
	path string,
	kind ast.ImportKind,
	absResolveDir string,
) (*resolver.ResolveResult, bool) {
	resolverArgs := config.OnResolveArgs{
		Path:       path,
		Importer:   importSource.KeyPath,
		ResolveDir: absResolveDir,
	}
	applyPath := logger.Path{Text: path, Namespace: importSource.KeyPath.Namespace}

	// Apply resolver plugins in order until one succeeds
	for _, plugin := range plugins {
		for _, onResolve := range plugin.OnResolve {
			if !config.PluginAppliesToPath(applyPath, onResolve.Filter, onResolve.Namespace) {
				continue
			}

			result := onResolve.Callback(resolverArgs)
			pluginName := result.PluginName
			if pluginName == "" {
				pluginName = plugin.Name
			}
			didLogError := logPluginMessages(res, log, pluginName, result.Msgs, result.ThrownError, importSource, importPathRange)

			// Stop now if there was an error
			if didLogError {
				return nil, true
			}

			// The "file" namespace is the default for non-external paths, but not
			// for external paths. External paths must explicitly specify the "file"
			// namespace.
			nsFromPlugin := result.Path.Namespace
			if result.Path.Namespace == "" && !result.External {
				result.Path.Namespace = "file"
			}

			// Otherwise, continue on to the next resolver if this loader didn't succeed
			if result.Path.Text == "" {
				if result.External {
					result.Path = logger.Path{Text: path}
				} else {
					continue
				}
			}

			// Paths in the file namespace must be absolute paths
			if result.Path.Namespace == "file" && !fs.IsAbs(result.Path.Text) {
				if nsFromPlugin == "file" {
					log.AddRangeError(importSource, importPathRange,
						fmt.Sprintf("Plugin %q returned a path in the \"file\" namespace that is not an absolute path: %s", pluginName, result.Path.Text))
				} else {
					log.AddRangeError(importSource, importPathRange,
						fmt.Sprintf("Plugin %q returned a non-absolute path: %s (set a namespace if this is not a file path)", pluginName, result.Path.Text))
				}
				return nil, true
			}

			return &resolver.ResolveResult{
				PathPair:   resolver.PathPair{Primary: result.Path},
				IsExternal: result.External,
			}, false
		}
	}

	// Resolve relative to the resolve directory by default. All paths in the
	// "file" namespace automatically have a resolve directory. Loader plugins
	// can also configure a custom resolve directory for files in other namespaces.
	return res.Resolve(absResolveDir, path, kind), false
}

type loaderPluginResult struct {
	loader        config.Loader
	absResolveDir string
	pluginName    string
}

func runOnLoadPlugins(
	plugins []config.Plugin,
	res resolver.Resolver,
	fs fs.FS,
	fsCache *cache.FSCache,
	log logger.Log,
	source *logger.Source,
	importSource *logger.Source,
	importPathRange logger.Range,
) (loaderPluginResult, bool) {
	loaderArgs := config.OnLoadArgs{
		Path: source.KeyPath,
	}

	// Apply loader plugins in order until one succeeds
	for _, plugin := range plugins {
		for _, onLoad := range plugin.OnLoad {
			if !config.PluginAppliesToPath(source.KeyPath, onLoad.Filter, onLoad.Namespace) {
				continue
			}

			result := onLoad.Callback(loaderArgs)
			pluginName := result.PluginName
			if pluginName == "" {
				pluginName = plugin.Name
			}
			didLogError := logPluginMessages(res, log, pluginName, result.Msgs, result.ThrownError, importSource, importPathRange)

			// Stop now if there was an error
			if didLogError {
				return loaderPluginResult{}, false
			}

			// Otherwise, continue on to the next loader if this loader didn't succeed
			if result.Contents == nil {
				continue
			}

			source.Contents = *result.Contents
			loader := result.Loader
			if loader == config.LoaderNone {
				loader = config.LoaderJS
			}
			if result.AbsResolveDir == "" && source.KeyPath.Namespace == "file" {
				result.AbsResolveDir = fs.Dir(source.KeyPath.Text)
			}
			return loaderPluginResult{
				loader:        loader,
				absResolveDir: result.AbsResolveDir,
				pluginName:    pluginName,
			}, true
		}
	}

	// Read normal modules from disk
	if source.KeyPath.Namespace == "file" {
		if contents, err := fsCache.ReadFile(fs, source.KeyPath.Text); err == nil {
			source.Contents = contents
			return loaderPluginResult{
				loader:        config.LoaderDefault,
				absResolveDir: fs.Dir(source.KeyPath.Text),
			}, true
		} else if err == syscall.ENOENT {
			log.AddRangeError(importSource, importPathRange,
				fmt.Sprintf("Could not read from file: %s", source.KeyPath.Text))
			return loaderPluginResult{}, false
		} else {
			log.AddRangeError(importSource, importPathRange,
				fmt.Sprintf("Cannot read file %q: %s", res.PrettyPath(source.KeyPath), err.Error()))
			return loaderPluginResult{}, false
		}
	}

	// Force disabled modules to be empty
	if source.KeyPath.Namespace == resolver.BrowserFalseNamespace {
		return loaderPluginResult{loader: config.LoaderJS}, true
	}

	// Otherwise, fail to load the path
	return loaderPluginResult{loader: config.LoaderNone}, true
}

func loaderFromFileExtension(extensionToLoader map[string]config.Loader, base string) config.Loader {
	// Pick the loader with the longest matching extension. So if there's an
	// extension for ".css" and for ".module.css", we want to match the one for
	// ".module.css" before the one for ".css".
	for {
		i := strings.IndexByte(base, '.')
		if i == -1 {
			break
		}
		if loader, ok := extensionToLoader[base[i:]]; ok {
			return loader
		}
		base = base[i+1:]
	}
	return config.LoaderNone
}

// Identify the path by its lowercase absolute path name. This should
// hopefully avoid path case issues on Windows, which has case-insensitive
// file system paths.
func lowerCaseAbsPathForWindows(absPath string) string {
	return strings.ToLower(absPath)
}

func hashForFileName(bytes []byte) string {
	hashBytes := sha1.Sum(bytes)
	return base32.StdEncoding.EncodeToString(hashBytes[:])[:8]
}

type scanner struct {
	log     logger.Log
	fs      fs.FS
	res     resolver.Resolver
	caches  *cache.CacheSet
	options config.Options

	// This is not guarded by a mutex because it's only ever modified by a single
	// thread. Note that not all results in the "results" array are necessarily
	// valid. Make sure to check the "ok" flag before using them.
	results       []parseResult
	visited       map[logger.Path]uint32
	resultChannel chan parseResult
	remaining     int
}

func ScanBundle(log logger.Log, fs fs.FS, res resolver.Resolver, caches *cache.CacheSet, entryPaths []string, options config.Options) Bundle {
	if options.ExtensionToLoader == nil {
		options.ExtensionToLoader = DefaultExtensionToLoaderMap()
	}

	s := scanner{
		log:           log,
		fs:            fs,
		res:           res,
		caches:        caches,
		options:       options,
		results:       make([]parseResult, 0, caches.SourceIndexCache.LenHint()),
		visited:       make(map[logger.Path]uint32),
		resultChannel: make(chan parseResult),
	}

	// Always start by parsing the runtime file
	s.results = append(s.results, parseResult{})
	s.remaining++
	go func() {
		source, ast, ok := globalRuntimeCache.parseRuntime(&options)
		s.resultChannel <- parseResult{file: file{source: source, repr: &reprJS{ast: ast}}, ok: ok}
	}()

	s.preprocessInjectedFiles()
	entryPoints := s.addEntryPoints(entryPaths)
	s.scanAllDependencies()
	files := s.processScannedFiles()

	return Bundle{
		fs:          fs,
		res:         res,
		files:       files,
		entryPoints: entryPoints,
	}
}

type inputKind uint8

const (
	inputKindNormal inputKind = iota
	inputKindEntryPoint
	inputKindStdin
)

// This returns the source index of the resulting file
func (s *scanner) maybeParseFile(
	resolveResult resolver.ResolveResult,
	prettyPath string,
	importSource *logger.Source,
	importPathRange logger.Range,
	kind inputKind,
	inject chan config.InjectedFile,
) uint32 {
	path := resolveResult.PathPair.Primary
	visitedKey := path
	if visitedKey.Namespace == "file" {
		visitedKey.Text = lowerCaseAbsPathForWindows(visitedKey.Text)
	}

	// Only parse a given file path once
	sourceIndex, ok := s.visited[visitedKey]
	if ok {
		return sourceIndex
	}

	sourceIndex = s.allocateSourceIndex(visitedKey, cache.SourceIndexNormal)
	s.visited[visitedKey] = sourceIndex
	s.remaining++
	optionsClone := s.options
	if kind != inputKindStdin {
		optionsClone.Stdin = nil
	}
	optionsClone.SuppressWarningsAboutWeirdCode = resolveResult.SuppressWarningsAboutWeirdCode

	// Allow certain properties to be overridden
	if len(resolveResult.JSXFactory) > 0 {
		optionsClone.JSX.Factory = resolveResult.JSXFactory
	}
	if len(resolveResult.JSXFragment) > 0 {
		optionsClone.JSX.Fragment = resolveResult.JSXFragment
	}
	if resolveResult.UseDefineForClassFieldsTS {
		optionsClone.UseDefineForClassFields = true
	}
	if resolveResult.PreserveUnusedImportsTS {
		optionsClone.PreserveUnusedImportsTS = true
	}

	// Enable bundling for injected files so we always do tree shaking. We
	// never want to include unnecessary code from injected files since they
	// are essentially bundled. However, if we do this we should skip the
	// resolving step when we're not bundling. It'd be strange to get
	// resolution errors when the top-level bundling controls are disabled.
	skipResolve := false
	if inject != nil && optionsClone.Mode != config.ModeBundle {
		optionsClone.Mode = config.ModeBundle
		skipResolve = true
	}

	go parseFile(parseArgs{
		fs:                 s.fs,
		log:                s.log,
		res:                s.res,
		caches:             s.caches,
		keyPath:            path,
		prettyPath:         prettyPath,
		sourceIndex:        sourceIndex,
		importSource:       importSource,
		ignoreIfUnused:     resolveResult.IgnorePrimaryIfUnused != nil,
		ignoreIfUnusedData: resolveResult.IgnorePrimaryIfUnused,
		importPathRange:    importPathRange,
		options:            optionsClone,
		results:            s.resultChannel,
		inject:             inject,
		skipResolve:        skipResolve,
	})

	return sourceIndex
}

func (s *scanner) allocateSourceIndex(path logger.Path, kind cache.SourceIndexKind) uint32 {
	// Allocate a source index using the shared source index cache so that
	// subsequent builds reuse the same source index and therefore use the
	// cached parse results for increased speed.
	sourceIndex := s.caches.SourceIndexCache.Get(path, kind)

	// Grow the results array to fit this source index
	if newLen := int(sourceIndex) + 1; len(s.results) < newLen {
		// Reallocate to a bigger array
		if cap(s.results) < newLen {
			s.results = append(make([]parseResult, 0, 2*newLen), s.results...)
		}

		// Grow in place
		s.results = s.results[:newLen]
	}

	return sourceIndex
}

func (s *scanner) preprocessInjectedFiles() {
	injectedFiles := make([]config.InjectedFile, 0, len(s.options.InjectAbsPaths))
	duplicateInjectedFiles := make(map[string]bool)
	injectWaitGroup := sync.WaitGroup{}
	for _, absPath := range s.options.InjectAbsPaths {
		prettyPath := s.res.PrettyPath(logger.Path{Text: absPath, Namespace: "file"})
		lowerAbsPath := lowerCaseAbsPathForWindows(absPath)

		if duplicateInjectedFiles[lowerAbsPath] {
			s.log.AddError(nil, logger.Loc{}, fmt.Sprintf("Duplicate injected file %q", prettyPath))
			continue
		}

		duplicateInjectedFiles[lowerAbsPath] = true
		resolveResult := s.res.ResolveAbs(absPath)

		if resolveResult == nil {
			s.log.AddError(nil, logger.Loc{}, fmt.Sprintf("Could not resolve %q", prettyPath))
			continue
		}

		i := len(injectedFiles)
		injectedFiles = append(injectedFiles, config.InjectedFile{})
		channel := make(chan config.InjectedFile)
		s.maybeParseFile(*resolveResult, prettyPath, nil, logger.Range{}, inputKindNormal, channel)

		// Wait for the results in parallel
		injectWaitGroup.Add(1)
		go func(i int, prettyPath string, resolveResult *resolver.ResolveResult) {
			injectedFiles[i] = <-channel
			injectWaitGroup.Done()
		}(i, prettyPath, resolveResult)
	}
	injectWaitGroup.Wait()
	s.options.InjectedFiles = injectedFiles
}

func (s *scanner) addEntryPoints(entryPaths []string) []uint32 {
	entryPoints := []uint32{}
	duplicateEntryPoints := make(map[string]bool)

	// Treat stdin as an extra entry point
	if s.options.Stdin != nil {
		resolveResult := resolver.ResolveResult{PathPair: resolver.PathPair{Primary: logger.Path{Text: "<stdin>"}}}
		sourceIndex := s.maybeParseFile(resolveResult, "<stdin>", nil, logger.Range{}, inputKindStdin, nil)
		entryPoints = append(entryPoints, sourceIndex)
	}

	// Add any remaining entry points
	for _, absPath := range entryPaths {
		prettyPath := s.res.PrettyPath(logger.Path{Text: absPath, Namespace: "file"})
		lowerAbsPath := lowerCaseAbsPathForWindows(absPath)

		if duplicateEntryPoints[lowerAbsPath] {
			s.log.AddError(nil, logger.Loc{}, fmt.Sprintf("Duplicate entry point %q", prettyPath))
			continue
		}

		duplicateEntryPoints[lowerAbsPath] = true
		resolveResult := s.res.ResolveAbs(absPath)

		if resolveResult == nil {
			s.log.AddError(nil, logger.Loc{}, fmt.Sprintf("Could not resolve %q", prettyPath))
			continue
		}

		sourceIndex := s.maybeParseFile(*resolveResult, prettyPath, nil, logger.Range{}, inputKindEntryPoint, nil)
		entryPoints = append(entryPoints, sourceIndex)
	}

	return entryPoints
}

func (s *scanner) scanAllDependencies() {
	// Continue scanning until all dependencies have been discovered
	for s.remaining > 0 {
		result := <-s.resultChannel
		s.remaining--
		if !result.ok {
			continue
		}

		// Don't try to resolve paths if we're not bundling
		if s.options.Mode == config.ModeBundle {
			records := *result.file.repr.importRecords()
			for importRecordIndex := range records {
				record := &records[importRecordIndex]

				// Skip this import record if the previous resolver call failed
				resolveResult := result.resolveResults[importRecordIndex]
				if resolveResult == nil {
					continue
				}

				path := resolveResult.PathPair.Primary
				if !resolveResult.IsExternal {
					// Handle a path within the bundle
					prettyPath := s.res.PrettyPath(path)
					sourceIndex := s.maybeParseFile(*resolveResult, prettyPath, &result.file.source, record.Range, inputKindNormal, nil)
					record.SourceIndex = &sourceIndex
				} else {
					// If the path to the external module is relative to the source
					// file, rewrite the path to be relative to the working directory
					if path.Namespace == "file" {
						if relPath, ok := s.fs.Rel(s.options.AbsOutputDir, path.Text); ok {
							// Prevent issues with path separators being different on Windows
							relPath = strings.ReplaceAll(relPath, "\\", "/")
							if resolver.IsPackagePath(relPath) {
								relPath = "./" + relPath
							}
							record.Path.Text = relPath
						} else {
							record.Path = path
						}
					} else {
						record.Path = path
					}
				}
			}
		}

		s.results[result.file.source.Index] = result
	}
}

func (s *scanner) processScannedFiles() []file {
	// Now that all files have been scanned, process the final file import records
	for i, result := range s.results {
		if !result.ok {
			continue
		}

		j := js_printer.Joiner{}
		isFirstImport := true

		// Begin the metadata chunk
		if s.options.AbsMetadataFile != "" {
			j.AddBytes(js_printer.QuoteForJSON(result.file.source.PrettyPath, s.options.ASCIIOnly))
			j.AddString(fmt.Sprintf(": {\n      \"bytes\": %d,\n      \"imports\": [", len(result.file.source.Contents)))
		}

		// Don't try to resolve paths if we're not bundling
		if s.options.Mode == config.ModeBundle {
			records := *result.file.repr.importRecords()
			for importRecordIndex := range records {
				record := &records[importRecordIndex]

				// Skip this import record if the previous resolver call failed
				resolveResult := result.resolveResults[importRecordIndex]
				if resolveResult == nil || record.SourceIndex == nil {
					continue
				}

				// Now that all files have been scanned, look for packages that are imported
				// both with "import" and "require". Rewrite any imports that reference the
				// "module" package.json field to the "main" package.json field instead.
				//
				// This attempts to automatically avoid the "dual package hazard" where a
				// package has both a CommonJS module version and an ECMAScript module
				// version and exports a non-object in CommonJS (often a function). If we
				// pick the "module" field and the package is imported with "require" then
				// code expecting a function will crash.
				if resolveResult.PathPair.HasSecondary() {
					secondaryKey := resolveResult.PathPair.Secondary
					if secondaryKey.Namespace == "file" {
						secondaryKey.Text = lowerCaseAbsPathForWindows(secondaryKey.Text)
					}
					if secondarySourceIndex, ok := s.visited[secondaryKey]; ok {
						record.SourceIndex = &secondarySourceIndex
					}
				}

				// Generate metadata about each import
				if s.options.AbsMetadataFile != "" {
					if isFirstImport {
						isFirstImport = false
						j.AddString("\n        ")
					} else {
						j.AddString(",\n        ")
					}
					j.AddString(fmt.Sprintf("{\n          \"path\": %s\n        }",
						js_printer.QuoteForJSON(s.results[*record.SourceIndex].file.source.PrettyPath, s.options.ASCIIOnly)))
				}

				// Importing a JavaScript file from a CSS file is not allowed.
				switch record.Kind {
				case ast.ImportAt:
					otherFile := &s.results[*record.SourceIndex].file
					if _, ok := otherFile.repr.(*reprJS); ok {
						s.log.AddRangeError(&result.file.source, record.Range,
							fmt.Sprintf("Cannot import %q into a CSS file", otherFile.source.PrettyPath))
					}

				case ast.ImportURL:
					otherFile := &s.results[*record.SourceIndex].file
					switch otherRepr := otherFile.repr.(type) {
					case *reprCSS:
						s.log.AddRangeError(&result.file.source, record.Range,
							fmt.Sprintf("Cannot use %q as a URL", otherFile.source.PrettyPath))

					case *reprJS:
						if otherRepr.ast.URLForCSS == "" {
							s.log.AddRangeError(&result.file.source, record.Range,
								fmt.Sprintf("Cannot use %q as a URL", otherFile.source.PrettyPath))
						}
					}
				}

				// If an import from a JavaScript file targets a CSS file, generate a
				// JavaScript stub to ensure that JavaScript files only ever import
				// other JavaScript files.
				if _, ok := result.file.repr.(*reprJS); ok {
					otherFile := &s.results[*record.SourceIndex].file
					if css, ok := otherFile.repr.(*reprCSS); ok {
						if s.options.WriteToStdout {
							s.log.AddRangeError(&result.file.source, record.Range,
								fmt.Sprintf("Cannot import %q into a JavaScript file without an output path configured", otherFile.source.PrettyPath))
						} else if css.jsSourceIndex == nil {
							stubKey := otherFile.source.KeyPath
							if stubKey.Namespace == "file" {
								stubKey.Text = lowerCaseAbsPathForWindows(stubKey.Text)
							}
							sourceIndex := s.allocateSourceIndex(stubKey, cache.SourceIndexJSStubForCSS)
							source := logger.Source{
								Index:      sourceIndex,
								PrettyPath: otherFile.source.PrettyPath,
							}
							s.results[sourceIndex] = parseResult{
								file: file{
									repr: &reprJS{
										ast: js_parser.LazyExportAST(s.log, source,
											js_parser.OptionsFromConfig(&s.options), js_ast.Expr{Data: &js_ast.EObject{}}, ""),
										cssSourceIndex: record.SourceIndex,
									},
									source: source,
								},
								ok: true,
							}
							css.jsSourceIndex = &sourceIndex
						}
						record.SourceIndex = css.jsSourceIndex
						if css.jsSourceIndex == nil {
							continue
						}
					}
				}

				// Don't include this module for its side effects if it can be
				// considered to have no side effects
				if record.WasOriginallyBareImport && !s.options.IgnoreDCEAnnotations {
					if otherFile := &s.results[*record.SourceIndex].file; otherFile.ignoreIfUnused {
						var notes []logger.MsgData
						if otherFile.ignoreIfUnusedData != nil {
							var text string
							if otherFile.ignoreIfUnusedData.IsSideEffectsArrayInJSON {
								text = "It was excluded from the \"sideEffects\" array in the enclosing \"package.json\" file"
							} else {
								text = "\"sideEffects\" is false in the enclosing \"package.json\" file"
							}
							notes = append(notes, logger.RangeData(otherFile.ignoreIfUnusedData.Source, otherFile.ignoreIfUnusedData.Range, text))
						}
						s.log.AddRangeWarningWithNotes(&result.file.source, record.Range,
							fmt.Sprintf("Ignoring this import because %q was marked as having no side effects",
								otherFile.source.PrettyPath), notes)
					}
				}
			}
		}

		// End the metadata chunk
		if s.options.AbsMetadataFile != "" {
			if !isFirstImport {
				j.AddString("\n      ")
			}
			j.AddString("]\n    }")
		}

		s.results[i].file.jsonMetadataChunk = j.Done()
	}

	// The linker operates on an array of files, so construct that now. This
	// can't be constructed earlier because we generate new parse results for
	// JavaScript stub files for CSS imports above.
	files := make([]file, len(s.results))
	for i, result := range s.results {
		if result.ok {
			files[i] = result.file
		}
	}
	return files
}

func DefaultExtensionToLoaderMap() map[string]config.Loader {
	return map[string]config.Loader{
		".js":   config.LoaderJS,
		".mjs":  config.LoaderJS,
		".cjs":  config.LoaderJS,
		".jsx":  config.LoaderJSX,
		".ts":   config.LoaderTS,
		".tsx":  config.LoaderTSX,
		".css":  config.LoaderCSS,
		".json": config.LoaderJSON,
		".txt":  config.LoaderText,
	}
}

type OutputFile struct {
	AbsPath  string
	Contents []byte

	// If "AbsMetadataFile" is present, this will be filled out with information
	// about this file in JSON format. This is a partial JSON file that will be
	// fully assembled later.
	jsonMetadataChunk []byte

	IsExecutable bool
}

func (b *Bundle) Compile(log logger.Log, options config.Options) []OutputFile {
	if options.ExtensionToLoader == nil {
		options.ExtensionToLoader = DefaultExtensionToLoaderMap()
	}
	if options.OutputExtensionJS == "" {
		options.OutputExtensionJS = ".js"
	}
	if options.OutputExtensionCSS == "" {
		options.OutputExtensionCSS = ".css"
	}

	// The format can't be "preserve" while bundling
	if options.Mode == config.ModeBundle && options.OutputFormat == config.FormatPreserve {
		options.OutputFormat = config.FormatESModule
	}

	// Get the base path from the options or choose the lowest common ancestor of all entry points
	if options.AbsOutputBase == "" {
		options.AbsOutputBase = b.lowestCommonAncestorDirectory(options.CodeSplitting)
	}

	type linkGroup struct {
		outputFiles    []OutputFile
		reachableFiles []uint32
	}

	var resultGroups []linkGroup
	if options.CodeSplitting {
		// If code splitting is enabled, link all entry points together
		c := newLinkerContext(&options, log, b.fs, b.res, b.files, b.entryPoints)
		resultGroups = []linkGroup{{
			outputFiles:    c.link(),
			reachableFiles: c.reachableFiles,
		}}
	} else {
		// Otherwise, link each entry point with the runtime file separately
		waitGroup := sync.WaitGroup{}
		resultGroups = make([]linkGroup, len(b.entryPoints))
		for i, entryPoint := range b.entryPoints {
			waitGroup.Add(1)
			go func(i int, entryPoint uint32) {
				c := newLinkerContext(&options, log, b.fs, b.res, b.files, []uint32{entryPoint})
				resultGroups[i] = linkGroup{
					outputFiles:    c.link(),
					reachableFiles: c.reachableFiles,
				}
				waitGroup.Done()
			}(i, entryPoint)
		}
		waitGroup.Wait()
	}

	// Join the results in entry point order for determinism
	var outputFiles []OutputFile
	for _, group := range resultGroups {
		outputFiles = append(outputFiles, group.outputFiles...)
	}

	// Also generate the metadata file if necessary
	if options.AbsMetadataFile != "" {
		outputFiles = append(outputFiles, OutputFile{
			AbsPath:  options.AbsMetadataFile,
			Contents: b.generateMetadataJSON(outputFiles, options.ASCIIOnly),
		})
	}

	if !options.WriteToStdout {
		// Make sure an output file never overwrites an input file
		sourceAbsPaths := make(map[string]uint32)
		for _, group := range resultGroups {
			for _, sourceIndex := range group.reachableFiles {
				keyPath := b.files[sourceIndex].source.KeyPath
				if keyPath.Namespace == "file" {
					lowerAbsPath := lowerCaseAbsPathForWindows(keyPath.Text)
					sourceAbsPaths[lowerAbsPath] = sourceIndex
				}
			}
		}
		for _, outputFile := range outputFiles {
			lowerAbsPath := lowerCaseAbsPathForWindows(outputFile.AbsPath)
			if sourceIndex, ok := sourceAbsPaths[lowerAbsPath]; ok {
				log.AddError(nil, logger.Loc{}, "Refusing to overwrite input file: "+b.files[sourceIndex].source.PrettyPath)
			}
		}

		// Make sure an output file never overwrites another output file. This
		// is almost certainly unintentional and would otherwise happen silently.
		//
		// Make an exception for files that have identical contents. In that case
		// the duplicate is just silently filtered out. This can happen with the
		// "file" loader, for example.
		outputFileMap := make(map[string][]byte)
		end := 0
		for _, outputFile := range outputFiles {
			lowerAbsPath := lowerCaseAbsPathForWindows(outputFile.AbsPath)
			contents, ok := outputFileMap[lowerAbsPath]

			// If this isn't a duplicate, keep the output file
			if !ok {
				outputFileMap[lowerAbsPath] = outputFile.Contents
				outputFiles[end] = outputFile
				end++
				continue
			}

			// If the names and contents are both the same, only keep the first one
			if bytes.Equal(contents, outputFile.Contents) {
				continue
			}

			// Otherwise, generate an error
			outputPath := outputFile.AbsPath
			if relPath, ok := b.fs.Rel(b.fs.Cwd(), outputPath); ok {
				outputPath = relPath
			}
			log.AddError(nil, logger.Loc{}, "Two output files share the same path but have different contents: "+outputPath)
		}
		outputFiles = outputFiles[:end]
	}

	return outputFiles
}

func (b *Bundle) lowestCommonAncestorDirectory(codeSplitting bool) string {
	isEntryPoint := make(map[uint32]bool)
	for _, entryPoint := range b.entryPoints {
		isEntryPoint[entryPoint] = true
	}

	// If code splitting is enabled, also treat dynamic imports as entry points
	if codeSplitting {
		for _, sourceIndex := range findReachableFiles(b.files, b.entryPoints) {
			if repr, ok := b.files[sourceIndex].repr.(*reprJS); ok {
				for importRecordIndex := range repr.ast.ImportRecords {
					if record := &repr.ast.ImportRecords[importRecordIndex]; record.SourceIndex != nil && record.Kind == ast.ImportDynamic {
						isEntryPoint[*record.SourceIndex] = true
					}
				}
			}
		}
	}

	// Ignore any paths for virtual modules (that don't exist on the file system)
	absPaths := make([]string, 0, len(isEntryPoint))
	for entryPoint := range isEntryPoint {
		keyPath := b.files[entryPoint].source.KeyPath
		if keyPath.Namespace == "file" {
			absPaths = append(absPaths, keyPath.Text)
		}
	}

	if len(absPaths) == 0 {
		return ""
	}

	lowestAbsDir := b.fs.Dir(absPaths[0])

	for _, absPath := range absPaths[1:] {
		absDir := b.fs.Dir(absPath)
		lastSlash := 0
		a := 0
		b := 0

		for {
			runeA, widthA := utf8.DecodeRuneInString(absDir[a:])
			runeB, widthB := utf8.DecodeRuneInString(lowestAbsDir[b:])
			boundaryA := widthA == 0 || runeA == '/' || runeA == '\\'
			boundaryB := widthB == 0 || runeB == '/' || runeB == '\\'

			if boundaryA && boundaryB {
				if widthA == 0 || widthB == 0 {
					// Truncate to the smaller path if one path is a prefix of the other
					lowestAbsDir = absDir[:a]
					break
				} else {
					// Track the longest common directory so far
					lastSlash = a
				}
			} else if boundaryA != boundaryB || unicode.ToLower(runeA) != unicode.ToLower(runeB) {
				// If both paths are different at this point, stop and set the lowest so
				// far to the common parent directory. Compare using a case-insensitive
				// comparison to handle paths on Windows.
				lowestAbsDir = absDir[:lastSlash]
				break
			}

			a += widthA
			b += widthB
		}
	}

	return lowestAbsDir
}

func (b *Bundle) generateMetadataJSON(results []OutputFile, asciiOnly bool) []byte {
	j := js_printer.Joiner{}
	j.AddString("{\n  \"inputs\": {")

	// Write inputs
	isFirst := true
	for _, sourceIndex := range findReachableFiles(b.files, b.entryPoints) {
		if sourceIndex == runtime.SourceIndex {
			continue
		}
		if file := &b.files[sourceIndex]; len(file.jsonMetadataChunk) > 0 {
			if isFirst {
				isFirst = false
				j.AddString("\n    ")
			} else {
				j.AddString(",\n    ")
			}
			j.AddBytes(file.jsonMetadataChunk)
		}
	}

	j.AddString("\n  },\n  \"outputs\": {")

	// Write outputs
	isFirst = true
	for _, result := range results {
		if len(result.jsonMetadataChunk) > 0 {
			if isFirst {
				isFirst = false
				j.AddString("\n    ")
			} else {
				j.AddString(",\n    ")
			}
			j.AddString(fmt.Sprintf("%s: ", js_printer.QuoteForJSON(b.res.PrettyPath(
				logger.Path{Text: result.AbsPath, Namespace: "file"}), asciiOnly)))
			j.AddBytes(result.jsonMetadataChunk)
		}
	}

	j.AddString("\n  }\n}\n")
	return j.Done()
}

type runtimeCacheKey struct {
	MangleSyntax      bool
	MinifyIdentifiers bool
	ES6               bool
	Platform          config.Platform
}

type runtimeCache struct {
	astMutex sync.Mutex
	astMap   map[runtimeCacheKey]js_ast.AST

	definesMutex sync.Mutex
	definesMap   map[config.Platform]*config.ProcessedDefines
}

var globalRuntimeCache runtimeCache

func (cache *runtimeCache) parseRuntime(options *config.Options) (source logger.Source, runtimeAST js_ast.AST, ok bool) {
	key := runtimeCacheKey{
		// All configuration options that the runtime code depends on must go here
		MangleSyntax:      options.MangleSyntax,
		MinifyIdentifiers: options.MinifyIdentifiers,
		Platform:          options.Platform,
		ES6:               runtime.CanUseES6(options.UnsupportedJSFeatures),
	}

	// Determine which source to use
	if key.ES6 {
		source = runtime.ES6Source
	} else {
		source = runtime.ES5Source
	}

	// Cache hit?
	(func() {
		cache.astMutex.Lock()
		defer cache.astMutex.Unlock()
		if cache.astMap != nil {
			runtimeAST, ok = cache.astMap[key]
		}
	})()
	if ok {
		return
	}

	// Cache miss
	var constraint int
	if key.ES6 {
		constraint = 2015
	} else {
		constraint = 5
	}
	log := logger.NewDeferLog()
	runtimeAST, ok = js_parser.Parse(log, source, js_parser.OptionsFromConfig(&config.Options{
		// These configuration options must only depend on the key
		MangleSyntax:      key.MangleSyntax,
		MinifyIdentifiers: key.MinifyIdentifiers,
		Platform:          key.Platform,
		Defines:           cache.processedDefines(key.Platform),
		UnsupportedJSFeatures: compat.UnsupportedJSFeatures(
			map[compat.Engine][]int{compat.ES: {constraint}}),

		// Always do tree shaking for the runtime because we never want to
		// include unnecessary runtime code
		Mode: config.ModeBundle,
	}))
	if log.HasErrors() {
		msgs := "Internal error: failed to parse runtime:\n"
		for _, msg := range log.Done() {
			msgs += msg.String(logger.StderrOptions{}, logger.TerminalInfo{})
		}
		panic(msgs[:len(msgs)-1])
	}

	// Cache for next time
	if ok {
		cache.astMutex.Lock()
		defer cache.astMutex.Unlock()
		if cache.astMap == nil {
			cache.astMap = make(map[runtimeCacheKey]js_ast.AST)
		}
		cache.astMap[key] = runtimeAST
	}
	return
}

func (cache *runtimeCache) processedDefines(key config.Platform) (defines *config.ProcessedDefines) {
	ok := false

	// Cache hit?
	(func() {
		cache.definesMutex.Lock()
		defer cache.definesMutex.Unlock()
		if cache.definesMap != nil {
			defines, ok = cache.definesMap[key]
		}
	})()
	if ok {
		return
	}

	// Cache miss
	var platform string
	switch key {
	case config.PlatformBrowser:
		platform = "browser"
	case config.PlatformNode:
		platform = "node"
	}
	result := config.ProcessDefines(map[string]config.DefineData{
		"__platform": {
			DefineFunc: func(logger.Loc, config.FindSymbol) js_ast.E {
				return &js_ast.EString{Value: js_lexer.StringToUTF16(platform)}
			},
		},
	})
	defines = &result

	// Cache for next time
	cache.definesMutex.Lock()
	defer cache.definesMutex.Unlock()
	if cache.definesMap == nil {
		cache.definesMap = make(map[config.Platform]*config.ProcessedDefines)
	}
	cache.definesMap[key] = defines
	return
}
