from __future__ import annotations

import ast
import contextlib
import dataclasses
import math
import re
import types
from collections.abc import Callable
from typing import TYPE_CHECKING, Any

from tracerite.logging import logger

if TYPE_CHECKING:
    from .trace.typing import VarInfo

# Minimum length for a string value to be considered a match against the
# exception message.  Short strings are too likely to collide with unrelated
# variables by accident.
_EXCEPTION_MESSAGE_MIN_MATCH_LEN = 12


def extract_variables(
    variables: dict[str, Any], sourcecode: str, exc_message: str | None = None
) -> list[VarInfo]:
    """Extract variable values that appear in sourcecode for display."""
    identifiers = _extract_identifiers_ast(sourcecode)
    if identifiers is None:
        identifiers = _extract_identifiers_regex(sourcecode)

    rows: list[VarInfo] = []
    for name, value in variables.items():
        if name in blacklist_names or isinstance(value, blacklist_types):
            continue
        try:
            rows.extend(
                _extract_variable_rows(
                    name, value, identifiers, sourcecode, exc_message
                )
            )
        except Exception:
            logger.exception("Variable inspector failed (please report a bug)")
    return rows


def _extract_variable_rows(
    name: str,
    value: Any,
    identifiers: set[str],
    sourcecode: str,
    exc_message: str | None,
) -> list[VarInfo]:
    """Return VarInfo rows for a single variable, expanding members if needed."""
    if name not in identifiers:
        return []

    try:
        strvalue = str(value)
        reprvalue = repr(value)
    except Exception:
        return []

    if not strvalue and reprvalue:
        strvalue = reprvalue

    typename = type(value).__name__
    if _is_exception_message_variable(strvalue, typename, exc_message):
        return []

    if no_str_conv.fullmatch(strvalue):
        member_rows = _extract_member_rows(name, value, identifiers, sourcecode)
        if member_rows:
            return member_rows
        value = "⋯"

    typename = _annotate_array_type(typename, value)
    val_str, val_fmt = prettyvalue(value)
    if typename == "NoneType":
        typename = ""
    return [
        {"name": name, "typename": typename, "value": val_str, "format_hint": val_fmt}
    ]


blacklist_names = {"_", "In", "Out"}
blacklist_types = (
    type,
    types.ModuleType,
    types.FunctionType,
    types.MethodType,
    types.BuiltinFunctionType,
)
no_str_conv = re.compile(r"<.* object at 0x[0-9a-fA-F]{5,}>")

# Superscript digits for formatting powers of 10
_SUPERSCRIPT_DIGITS = str.maketrans("-0123456789", "⁻⁰¹²³⁴⁵⁶⁷⁸⁹")


def _format_scalar(v: Any) -> str:
    """Format a single numeric value intelligently."""
    dtype = str(v.dtype) if hasattr(v, "dtype") else ""
    if isinstance(v, int) or "int" in dtype:
        return str(int(v))
    if isinstance(v, float) or "float" in dtype:
        v = float(v)
        if math.isnan(v):
            return "NaN"
        if math.isinf(v):
            return "∞" if v > 0 else "\u2212∞"
        if v == 0:
            return "0"
        if v == int(v) and abs(v) < 1e15:
            return str(int(v))
        # Compact fixed-point: strip trailing zeros
        return f"{v:.6f}".rstrip("0").rstrip(".")
    return str(v)


def _get_flat(arr: Any) -> Any:
    """Get a flat/1D view of an array, supporting numpy and torch."""
    if hasattr(arr, "flat"):
        return arr.flat
    if hasattr(arr, "flatten"):
        return arr.flatten()
    return arr


def _array_formatter(arr: Any) -> tuple[Callable[[Any], str], str]:
    """Create an optimal formatter for displaying array values consistently."""
    try:
        dtype_str = str(arr.dtype)
    except AttributeError:
        dtype_str = ""

    # Integer arrays - display as integers, no scaling
    if "int" in dtype_str or "bool" in dtype_str:
        return lambda v: str(int(v)), ""

    # For float arrays, analyze the values to determine optimal formatting
    if "float" in dtype_str or "complex" in dtype_str:
        flat = _get_flat(arr)
        n = len(flat)
        sample = [float(v) for v in (flat if n <= 200 else (*flat[:100], *flat[-100:]))]

        finite = [abs(v) for v in sample if math.isfinite(v)]
        if not finite:
            return (
                lambda v: (
                    "NaN" if math.isnan(float(v)) else ("∞" if v > 0 else "\u2212∞")
                ),
                "",
            )

        max_abs = max(finite)
        log_max = math.log10(max_abs) if max_abs > 0 else 0
        scale_power = int(log_max // 3) * 3
        if scale_power in (-3, 0, 3):
            scale_power = 0
        scale_suffix = (
            f"×10{str(scale_power).translate(_SUPERSCRIPT_DIGITS)}"
            if scale_power
            else ""
        )
        scale_factor = 10.0 ** (-scale_power) if scale_power else 1.0
        log_scaled = log_max - scale_power if scale_power else log_max
        decimals = max(0, 2 - math.floor(log_scaled)) if max_abs > 0 else 0

        def fmt(v: Any, sf: float = scale_factor, d: int = decimals) -> str:
            v = float(v)
            if math.isnan(v):
                return "NaN"
            if math.isinf(v):
                return "∞" if v > 0 else "\u2212∞"
            scaled = v * sf
            if scaled == 0:
                return "0"
            return f"{scaled:.{d}f}"

        return fmt, scale_suffix

    return lambda v: f"{v}", ""


class _IdentifierVisitor(ast.NodeVisitor):
    """AST visitor that collects variable identifiers from source code."""

    def __init__(self):
        self.identifiers: set[str] = set()

    def visit_Name(self, node: ast.Name) -> None:
        self.identifiers.add(node.id)
        self.generic_visit(node)

    def visit_Attribute(self, node: ast.Attribute) -> None:
        parts: list[str] = []
        current: ast.AST = node
        while isinstance(current, ast.Attribute):
            parts.append(current.attr)
            current = current.value
        if isinstance(current, ast.Name):
            parts.append(current.id)
            self.identifiers.update(
                ".".join(reversed(parts[i:])) for i in range(len(parts))
            )
        self.generic_visit(node)


def _extract_identifiers_ast(sourcecode: str) -> set[str] | None:
    """Extract variable identifiers from source code using AST."""
    tree: ast.AST | None = None
    for wrapper in ("({})", "{}"):
        with contextlib.suppress(SyntaxError):
            tree = ast.parse(wrapper.format(sourcecode), mode="eval")
            break
    if tree is None:
        with contextlib.suppress(SyntaxError):
            tree = ast.parse(sourcecode, mode="exec")
    if tree is None:
        return None

    visitor = _IdentifierVisitor()
    visitor.visit(tree)
    return visitor.identifiers


def _extract_identifiers_regex(sourcecode: str) -> set[str]:
    """Extract variable identifiers from source code using regex (fallback)."""
    return {
        m.group(0) for p in (r"\w+", r"\w+\.\w+") for m in re.finditer(p, sourcecode)
    }


def _is_exception_message_variable(
    strvalue: str, typename: str, exc_message: str | None
) -> bool:
    """Check whether a string variable is the exception message itself."""
    return (
        typename == "str"
        and exc_message is not None
        and len(exc_message) >= _EXCEPTION_MESSAGE_MIN_MATCH_LEN
        and strvalue == exc_message
    )


def _safe_str(obj: Any) -> str | None:
    """Return str(obj), or None if it raises."""
    with contextlib.suppress(Exception):
        return str(obj)
    return None


def _extract_member_rows(
    name: str, value: Any, identifiers: set[str], sourcecode: str
) -> list[VarInfo]:
    """Extract members of an object with a poor __str__ representation."""
    try:
        members = safe_vars(value).items()
    except Exception:
        members = []

    typename = type(value).__name__
    return [
        {
            "name": mname,
            "typename": f"{type(v).__name__} in {typename}",
            "value": val,
            "format_hint": fmt,
        }
        for n, v in members
        if (not sourcecode or (mname := f"{name}.{n}") in identifiers)
        and not isinstance(v, blacklist_types)
        and (member_str := _safe_str(v)) is not None
        and not no_str_conv.fullmatch(member_str)
        for val, fmt in [prettyvalue(v)]
    ]


def _annotate_array_type(typename: str, value: Any) -> str:
    """Append dtype/shape/device info for array/tensor-like values."""
    try:
        dtype = str(object.__getattribute__(value, "dtype")).rsplit(".", 1)[-1]
        if typename == dtype:
            raise AttributeError
        shape = object.__getattribute__(value, "shape")
        dims = "×".join(str(d) for d in shape) + " " if shape else ""
        dev = ""
        with contextlib.suppress(AttributeError):
            device = object.__getattribute__(value, "device")
            if device and device.type != "cpu":
                dev = f"@{device}"
        return f"{typename} of {dims}{dtype}{dev}"
    except AttributeError:
        return typename


_MISSING = object()


def _get_attr_safe(obj: Any, attr: str) -> Any:
    """Return object.__getattribute__(obj, attr), or _MISSING if it raises."""
    with contextlib.suppress(AttributeError):
        return object.__getattribute__(obj, attr)
    return _MISSING


def safe_vars(obj: Any) -> dict[str, Any]:
    """Like vars(), but also supports objects with slots."""
    return {
        attr: val
        for attr in dir(obj)
        if (val := _get_attr_safe(obj, attr)) is not _MISSING
    }


def prettyvalue(val: Any) -> tuple[Any, str]:
    """
    Format a value for display in the inspector.

    Returns:
        tuple: (formatted_value, format_hint) where format_hint is one of:
               'block' - left-aligned block format (for multi-line strings)
               'inline' - inline right-aligned format (default)
    """
    result = _format_keyvalue_container(val)
    if result is not None:
        return result

    if isinstance(val, (list, tuple)):
        if 0 < len(val) <= 10:
            return (", ".join(repr(v)[:80] for v in val), "inline")
        return (f"({len(val)} items)", "inline")

    if isinstance(val, type):
        return (f"{val.__module__}.{val.__name__}", "inline")

    result = _format_array_like(val)
    if result is not None:
        return result

    result = _format_scalar_value(val)
    if result is not None:
        return result

    return _format_default_value(val)


def _format_keyvalue_container(val: Any) -> tuple[Any, str] | None:
    """Format namedtuple, dict, dataclass, or struct as a key-value table."""
    if (
        isinstance(val, tuple)
        and hasattr(val, "_fields")
        and isinstance(val._fields, tuple)
    ):
        return _build_keyvalue_table(val, val._fields, "fields", getattr)
    if isinstance(val, dict):
        if not val:
            return ("{}", "inline")
        return _build_keyvalue_table(val, list(val.keys()), "items", lambda d, k: d[k])
    if dataclasses.is_dataclass(val) and not isinstance(val, type):
        return _build_keyvalue_table(
            val,
            [f.name for f in dataclasses.fields(val)],
            "fields",
            object.__getattribute__,
        )
    struct_fields = _struct_fields(val)
    if struct_fields is not None:
        return _build_keyvalue_table(
            val, struct_fields, "fields", object.__getattribute__
        )
    return None


def _truncated(s: str, limit: int = 60) -> str:
    """Truncate a string with an ellipsis if it exceeds the limit."""
    return s if len(s) <= limit else s[: limit - 3] + "…"


def _build_keyvalue_table(
    val: Any,
    fields: tuple[Any, ...] | list[Any],
    item_label: str,
    getter: Callable[[Any, Any], Any],
) -> tuple[Any, str]:
    """Build a key-value table or summary for a container with named fields."""
    if not fields:
        return (f"{type(val).__name__}()", "inline")
    if len(fields) > 10:
        return (f"({len(fields)} {item_label})", "inline")

    rows = [
        [_truncated(name, 40), _truncated(f"{getter(val, name)!s}", 60)]
        for name in fields
    ]
    return ({"type": "keyvalue", "rows": rows}, "inline")


def _struct_fields(val: Any) -> tuple[str, ...] | None:
    """Return field names for msgspec Struct or Pydantic BaseModel, if applicable."""
    if isinstance(fields := getattr(type(val), "__struct_fields__", None), tuple):
        return fields
    if isinstance(fields := getattr(type(val), "model_fields", None), dict):
        return tuple(fields.keys())
    return None


def _format_array_like(val: Any) -> tuple[Any, str] | None:
    """Format numpy/torch arrays and similar array-like objects."""
    try:
        shape = object.__getattribute__(val, "shape")
        if not (isinstance(shape, tuple) and shape):
            return None

        if math.prod(shape) <= 1:
            flat = _get_flat(val)
            return (_format_scalar(flat[0]), "inline")

        if len(shape) == 1:
            return _format_1d_array(val, shape[0])

        if len(shape) == 2 and shape[0] <= 10 and shape[1] <= 10:
            return _format_2d_array(val)
    except (AttributeError, ValueError):
        return None
    except Exception:
        logger.exception(
            "Pretty-printing in variable inspector failed (please report a bug)"
        )
    return None


def _format_1d_array(val: Any, length: int) -> tuple[str, str]:
    """Format a one-dimensional array."""
    fmt, suffix = _array_formatter(val)
    if length <= 100:
        result = ", ".join(fmt(v) for v in val)
    else:
        items = [fmt(v) for v in (*val[:3], *val[-3:])]
        result = ", ".join([*items[:3], "…", *items[-3:]])
    return (f"{result} {suffix}".rstrip(), "inline")


def _format_2d_array(val: Any) -> tuple[Any, str]:
    """Format a small two-dimensional array."""
    fmt, suffix = _array_formatter(val)
    table = [[fmt(v) for v in row] for row in val]
    if suffix:
        return ({"type": "array", "rows": table, "suffix": suffix}, "inline")
    return table, "inline"


def _format_scalar_value(val: Any) -> tuple[Any, str] | None:
    """Format numpy scalars and plain numeric values."""
    try:
        dtype_str = str(getattr(val, "dtype", ""))
        shape = getattr(val, "shape", ())
        is_scalar = not shape or (isinstance(shape, tuple) and len(shape) == 0)
        if (
            isinstance(val, (int, float)) or (dtype_str and is_scalar)
        ) and not isinstance(val, bool):
            return (_format_scalar(val), "inline")
    except (AttributeError, TypeError, ValueError):
        pass
    return None


def _format_default_value(val: Any) -> tuple[Any, str]:
    """Format arbitrary values using str/repr and apply truncation rules."""
    if isinstance(val, BaseException):
        ret = str(val)
    elif isinstance(val, str):
        ret = str(val)
        if "\n" in ret.rstrip():
            return _format_block_string(ret)
        return _format_inline_string(ret)
    else:
        ret = repr(val)

    return _format_inline_string(ret)


def _format_inline_string(ret: str) -> tuple[str, str]:
    """Collapse newlines and truncate long single-line values."""
    if "\n" in ret:
        ret = " ".join(line.strip() for line in ret.split("\n") if line.strip())
    if len(ret) > 120:
        ret = ret[:30] + " … " + ret[-30:]
    return ret, "inline"


def _format_block_string(ret: str) -> tuple[str, str]:
    """Format multi-line strings, truncating very long ones."""
    lines = ret.split("\n")
    if len(lines) <= 15:
        return ret, "block"

    first = lines[:5]
    while first and first[-1].strip() == "":
        first.pop()

    last = [line for line in reversed(lines) if line.strip() != ""][:2]
    last.reverse()

    return "\n".join(first + ["⋮"] + last), "block"
