#!/usr/bin/env python
"""
Migrate Python Lib files from CPython, preserving explicit local adaptations.

Usage:
    python scripts/update_lib migrate cpython/Lib/test/test_foo.py
    python scripts/update_lib migrate cpython/Lib/test/test_foo.py --patches remaining.json

Remaining metadata names the exact repository-relative target and its existing
decorator patches. An optional "doctests" object selects existing guarded inputs
by exact source text, mapping each to a single-line reason. Guarded doctests need
this explicit selection; an empty object retires all their guards. Canonical
expected output is never copied from the old file. Optional "blocks" lists
[canonical, local] source pairs to preserve exact existing changes.
Both fragments must match uniquely; no module-specific defaults are inferred.
Non-marker adaptations require reviewed blocks on each migration, for example
{"target": "Lib/example.py", "patches": {}, "blocks": [["old = 1", "old = 2"]]}.
Use a host Python that parses the source version (Python 3.15 for 3.15 syntax),
as required by the existing marker extraction and application steps.

This will:
    1. Extract patches from Lib/test/test_foo.py (if exists)
    2. Apply them to cpython/Lib/test/test_foo.py
    3. Write result to Lib/test/test_foo.py
"""

import argparse
import ast
import collections
import json
import pathlib
import shutil
import sys

sys.path.insert(0, str(pathlib.Path(__file__).parent.parent))

from update_lib.file_utils import parse_lib_path


def _preserve_block(old, new, canonical, local):
    """Preserve an explicit existing fragment; do not infer module adaptations."""
    if old.count(local) != 1 or new.count(canonical) != 1:
        raise ValueError("Changed or ambiguous preservation block")
    return new.replace(canonical, local, 1)


def patch_single_content(
    src_path: pathlib.Path,
    lib_path: pathlib.Path,
    patches_document: dict | None = None,
) -> str:
    """
    Patch content without writing to disk.

    Args:
        src_path: Source file path (e.g., cpython/Lib/test/foo.py)
        lib_path: Lib path to extract patches from (e.g., Lib/test/foo.py)

    Returns:
        The patched content.
    """
    from update_lib import apply_patches, extract_patches
    from update_lib.patch_spec import apply_doctest_metadata, extract_doctest_guards

    # Extract patches from existing file (if exists)
    if lib_path.exists():
        old_content = lib_path.read_text(encoding="utf-8")
        patches = extract_patches(old_content)
    else:
        patches = {}

    repository = pathlib.Path(__file__).resolve().parents[2]
    try:
        relative_path = lib_path.resolve().relative_to(repository)
    except ValueError:
        # Explicit output paths outside this repository are not its Lib.
        relative_path = pathlib.Path("__external_output__")
    if patches_document is not None:
        from update_lib.patch_spec import select_remaining_patches

        patches = select_remaining_patches(
            patches,
            patches_document,
            relative_path,
            old_content=old_content if lib_path.exists() else None,
        )

    blocks = patches_document.get("blocks", []) if patches_document else []
    if not isinstance(blocks, list) or any(
        not isinstance(pair, list)
        or len(pair) != 2
        or any(not isinstance(text, str) or not text.strip() for text in pair)
        for pair in blocks
    ):
        raise ValueError("Blocks must be canonical/local source pairs")
    if blocks and not lib_path.exists():
        raise ValueError("Blocks require an existing local file")

    # Apply patches to source content
    src_content = src_path.read_text(encoding="utf-8")
    if lib_path.exists():
        if any(src_content.count(canonical) != 1 for canonical, _ in blocks):
            raise ValueError("Changed or ambiguous canonical preservation block")
        for canonical, local in blocks:
            src_content = _preserve_block(old_content, src_content, canonical, local)
        guards = extract_doctest_guards(old_content)
        selection = patches_document.get("doctests") if patches_document else None
        if guards and selection is None:
            raise ValueError(
                "Existing doctest guards require explicit doctests metadata"
            )
        if selection is not None:
            src_content = apply_doctest_metadata(old_content, src_content, selection)
    if not src_content and not patches:
        return src_content
    try:
        result = apply_patches(src_content, patches)
    except SyntaxError as error:
        if blocks:
            raise ValueError("Preserved blocks produced invalid Python") from error
        raise
    return result


def patch_file(
    src_path: pathlib.Path,
    lib_path: pathlib.Path | None = None,
    verbose: bool = True,
    patches_document: dict | None = None,
) -> None:
    """
    Patch a single file from source to lib.

    Args:
        src_path: Source file path (e.g., cpython/Lib/test/foo.py)
        lib_path: Target lib path. If None, derived from src_path.
        verbose: Print progress messages
    """
    if lib_path is None:
        lib_path = parse_lib_path(src_path)

    if lib_path.exists():
        if verbose:
            print(f"Patching: {src_path} -> {lib_path}")
        content = patch_single_content(src_path, lib_path, patches_document)
    else:
        if verbose:
            print(f"Copying: {src_path} -> {lib_path}")
        if patches_document is not None:
            raise ValueError("Marker override requires an existing target")
        content = src_path.read_text(encoding="utf-8")

    lib_path.parent.mkdir(parents=True, exist_ok=True)
    lib_path.write_text(content, encoding="utf-8")


def patch_directory(
    src_dir: pathlib.Path,
    lib_dir: pathlib.Path | None = None,
    verbose: bool = True,
) -> None:
    """
    Patch all files in a directory from source to lib.

    Args:
        src_dir: Source directory path (e.g., cpython/Lib/test/test_foo/)
        lib_dir: Target lib directory. If None, derived from src_dir.
        verbose: Print progress messages
    """
    if lib_dir is None:
        lib_dir = parse_lib_path(src_dir)

    src_files = sorted(
        f
        for f in src_dir.glob("**/*")
        if f.is_file() and "__pycache__" not in f.relative_to(src_dir).parts[:-1]
    )

    for src_file in src_files:
        rel_path = src_file.relative_to(src_dir)
        lib_file = lib_dir / rel_path

        if src_file.suffix == ".py":
            if lib_file.exists():
                if verbose:
                    print(f"Patching: {src_file} -> {lib_file}")
                content = patch_single_content(src_file, lib_file)
            else:
                if verbose:
                    print(f"Copying: {src_file} -> {lib_file}")
                content = src_file.read_text(encoding="utf-8")

            lib_file.parent.mkdir(parents=True, exist_ok=True)
            lib_file.write_text(content, encoding="utf-8")
        else:
            if verbose:
                print(f"Copying: {src_file} -> {lib_file}")
            lib_file.parent.mkdir(parents=True, exist_ok=True)
            shutil.copy2(src_file, lib_file)


def retire_legacy_paths(src_dir: pathlib.Path, mapping: dict) -> None:
    """Retire explicit upstream-absent files after checking their replacements.

    Flat legacy maps use repository-relative Lib paths and name an already
    canonical replacement, or null for an upstream removal. They never rewrite
    replacements or recursively prune directories.
    """
    from update_lib.file_utils import get_cpython_dir

    canonical = get_cpython_dir(src_dir).resolve()
    local = pathlib.Path.cwd().resolve()
    if not (canonical / "Lib").is_dir() or not src_dir.is_dir():
        raise ValueError("Canonical Lib or migration source directory does not exist")

    def lib_file(root, name):
        path = pathlib.Path(name)
        if path.is_absolute() or ".." in path.parts or path.parts[:1] != ("Lib",):
            raise ValueError(f"Expected a repository-relative Lib file: {name}")
        result = root / path
        if result.is_symlink() or not result.resolve().is_relative_to(root / "Lib"):
            raise ValueError(f"Lib file escapes its source tree: {name}")
        return result

    legacy_files = []
    for old, new in mapping.items():
        legacy = lib_file(local, old)
        upstream_old = lib_file(canonical, old)
        if upstream_old.exists() or not legacy.is_file():
            raise ValueError(f"Not an existing upstream-absent file: {old}")
        if new is not None:
            replacement = lib_file(local, new)
            upstream_new = lib_file(canonical, new)
            if (
                not upstream_new.is_file()
                or not replacement.is_file()
                or replacement.read_bytes() != upstream_new.read_bytes()
            ):
                raise ValueError(f"Replacement is not canonical: {new}")
        legacy_files.append(legacy)

    # Check the whole map before retiring any file.
    for legacy in legacy_files:
        legacy.unlink()


def migrate_package(
    src_dir: pathlib.Path, lib_dir: pathlib.Path, mapping_path: pathlib.Path
) -> None:
    """Validate the complete migration before writing or removing legacy files.

    The JSON map names legacy files beside lib_dir, mapping every marked class
    to its canonical file relative to src_dir. Empty maps retire unmarked files.
    No test modules are imported or executed.
    """
    from update_lib.patch_spec import (
        _iter_class_methods,
        _iter_module_classes,
        apply_patches,
        build_patch_dict,
        extract_doctest_guards,
        iter_patches,
    )

    mapping = json.loads(mapping_path.read_text(encoding="utf-8"))
    if not isinstance(mapping, dict) or not mapping:
        raise ValueError("Legacy mapping must be a nonempty object")
    if all(value is None or isinstance(value, str) for value in mapping.values()):
        retire_legacy_paths(src_dir, mapping)
        return
    if lib_dir.exists():
        raise ValueError(f"Destination already exists: {lib_dir}")
    if (
        src_dir.resolve() == lib_dir.resolve()
        or src_dir.resolve() in lib_dir.resolve().parents
    ):
        raise ValueError("Source and destination overlap")
    source_files = sorted(
        p
        for p in src_dir.rglob("*")
        if p.is_file() and "__pycache__" not in p.relative_to(src_dir).parts[:-1]
    )
    if not (src_dir / "__init__.py").is_file():
        raise ValueError("Source must be a Python package")
    if any(
        p.is_symlink() or src_dir.resolve() not in p.resolve().parents
        for p in source_files
    ):
        raise ValueError("Source files must remain inside the canonical package")
    contents = {p.relative_to(src_dir): p.read_bytes() for p in source_files}
    entries = collections.defaultdict(list)
    owners = {}
    legacy_files = []
    for name, class_map in mapping.items():
        if pathlib.Path(name).name != name or not name.endswith(".py"):
            raise ValueError(f"Legacy file must be a sibling .py file: {name}")
        if not isinstance(class_map, dict):
            raise ValueError(f"Class map must be an object: {name}")
        legacy = lib_dir.parent / name
        if legacy.is_symlink() or legacy.resolve().parent != lib_dir.parent.resolve():
            raise ValueError(f"Legacy file escapes destination parent: {name}")
        if (
            legacy.resolve() == lib_dir.resolve()
            or src_dir.resolve() in legacy.resolve().parents
        ):
            raise ValueError(f"Legacy file overlaps canonical package: {name}")
        legacy_files.append(legacy)
        legacy_content = legacy.read_text(encoding="utf-8")
        if extract_doctest_guards(legacy_content):
            raise ValueError("Legacy package migration cannot select doctest guards")
        patches = list(iter_patches(legacy_content))
        legacy_classes = collections.defaultdict(list)
        for cls in _iter_module_classes(ast.parse(legacy_content)):
            legacy_classes[cls.name].append(cls)
        if set(class_map) != {p.parent_class for p in patches}:
            raise ValueError(f"Missing or unused class mapping: {name}")
        for entry in patches:
            source_classes = legacy_classes[entry.parent_class]
            if len(source_classes) != 1:
                raise ValueError(f"Ambiguous legacy class: {entry.parent_class}")
            if (
                entry.test_name != "__self__"
                and sum(
                    method.name == entry.test_name
                    for method in _iter_class_methods(source_classes[0])
                )
                != 1
            ):
                raise ValueError(
                    f"Ambiguous legacy method: {entry.parent_class}.{entry.test_name}"
                )
            target = pathlib.Path(class_map[entry.parent_class])
            if target.is_absolute() or ".." in target.parts or target not in contents:
                raise ValueError(f"Invalid canonical destination: {target}")
            if target.suffix != ".py":
                raise ValueError(f"Marker destination is not Python: {target}")
            tree = ast.parse(contents[target].decode("utf-8"))
            classes = collections.defaultdict(list)
            for cls in _iter_module_classes(tree):
                classes[cls.name].append(cls)

            def has_method(class_name, seen):
                if class_name in seen:
                    return False
                seen = seen | {class_name}
                nodes = classes.get(class_name, [])
                if len(nodes) != 1:
                    raise ValueError(f"Missing or ambiguous class: {class_name}")
                cls = nodes[0]
                methods = [
                    m for m in _iter_class_methods(cls) if m.name == entry.test_name
                ]
                if len(methods) > 1:
                    raise ValueError(
                        f"Ambiguous method: {class_name}.{entry.test_name}"
                    )
                if methods or entry.test_name == "__self__":
                    return True
                return any(
                    has_method(base.id, seen)
                    for base in cls.bases
                    if isinstance(base, ast.Name) and base.id in classes
                )

            if not has_method(entry.parent_class, set()):
                raise ValueError(
                    f"Missing method: {entry.parent_class}.{entry.test_name}"
                )
            owner_key = (target, entry.parent_class, entry.test_name)
            if owner_key in owners and owners[owner_key] != legacy:
                raise ValueError(
                    f"Duplicate mapped marker: {entry.parent_class}.{entry.test_name}"
                )
            owners[owner_key] = legacy
            entries[target].append(entry)
    # Render and validate everything before changing the destination.
    for target, patches in entries.items():
        contents[target] = apply_patches(
            contents[target].decode("utf-8"), build_patch_dict(iter(patches))
        ).encode("utf-8")
    for target, data in contents.items():
        if target.suffix == ".py":
            text = data.decode("utf-8")
            ast.parse(text)
            if collections.Counter(iter_patches(text)) != collections.Counter(
                entries[target]
            ):
                raise ValueError(f"Marker roundtrip mismatch: {target}")
    for target, data in contents.items():
        destination = lib_dir / target
        destination.parent.mkdir(parents=True, exist_ok=True)
        destination.write_bytes(data)
    for legacy in legacy_files:
        legacy.unlink()


def main(argv: list[str] | None = None) -> int:
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawDescriptionHelpFormatter,
    )
    parser.add_argument(
        "path",
        type=pathlib.Path,
        help="Source path containing /Lib/ (file or directory)",
    )

    parser.add_argument(
        "--legacy-map",
        type=pathlib.Path,
        help="Legacy class mapping, or exact Lib path to canonical replacement/null map",
    )
    parser.add_argument(
        "--patches",
        type=pathlib.Path,
        help="Single-file target, remaining decorator patches, and optional doctests JSON",
    )
    args = parser.parse_args(argv)

    try:
        if args.patches is not None and (
            args.path.is_dir() or args.legacy_map is not None
        ):
            raise ValueError("--patches requires a single file without --legacy-map")
        document = (
            json.loads(args.patches.read_text()) if args.patches is not None else None
        )
        if args.legacy_map is not None:
            migrate_package(args.path, parse_lib_path(args.path), args.legacy_map)
        elif args.path.is_dir():
            patch_directory(args.path)
        else:
            patch_file(args.path, patches_document=document)
        return 0
    except ValueError as e:
        print(f"Error: {e}", file=sys.stderr)
        return 1
    except FileNotFoundError as e:
        print(f"Error: {e}", file=sys.stderr)
        return 1


if __name__ == "__main__":
    sys.exit(main())