from __future__ import annotations

import ast
import hashlib
import re
from pathlib import Path


APP_ROOT = Path(__file__).resolve().parents[1]
ORIGINAL_ROOT = APP_ROOT.parent
FRONTEND_ROOT = APP_ROOT / "frontend"
ORIGINAL_STATIC = ORIGINAL_ROOT / "static"

SOURCE_RANGE = re.compile(
    r"/\* PRESERVATION-SOURCE-BEGIN app\.js:(\d+)-(\d+) \*/\n"
    r"(.*?)"
    r"/\* PRESERVATION-SOURCE-END app\.js:\1-\2 \*/\n?",
    re.DOTALL,
)

# These exact original app.js line ranges were retired in slice 11 after the
# definition-only symbols passed static, runtime, and compatibility review.
RETIRED_FRONTEND_SOURCE_RANGES = (
    (3537, 3540),
    (4139, 4145),
    (4973, 4989),
    (9022, 9027),
    (9052, 9055),
)
AUDITED_FRONTEND_SOURCE_LINE_COUNT = 9283


def sha256(path: Path) -> str:
    return hashlib.sha256(path.read_bytes()).hexdigest()


def function_contract(path: Path, name: str) -> tuple[str, str]:
    tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
    function = next(
        node for node in tree.body if isinstance(node, ast.FunctionDef) and node.name == name
    )
    body = ast.Module(body=function.body, type_ignores=[])
    return (
        ast.dump(function.args, include_attributes=False),
        ast.dump(body, include_attributes=False),
    )


def module_contract(
    path: Path,
    *,
    excluded_definitions: set[str] | None = None,
    excluded_import_modules: set[str] | None = None,
    exclude_imports: bool = False,
) -> str:
    excluded_definitions = excluded_definitions or set()
    excluded_import_modules = excluded_import_modules or set()
    tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
    tree.body = [
        node
        for node in tree.body
        if not (exclude_imports and isinstance(node, (ast.Import, ast.ImportFrom)))
        and not (
            isinstance(node, ast.ImportFrom)
            and node.module in excluded_import_modules
        )
        and getattr(node, "name", None) not in excluded_definitions
    ]
    return ast.dump(tree, include_attributes=False)


def reassembled_frontend_runtime() -> str:
    chunks: dict[tuple[int, int], str] = {}
    for path in FRONTEND_ROOT.rglob("*.js"):
        for match in SOURCE_RANGE.finditer(path.read_text(encoding="utf-8")):
            source_range = (int(match.group(1)), int(match.group(2)))
            if source_range in chunks:
                raise AssertionError(f"duplicate app.js source range: {source_range}")
            chunks[source_range] = match.group(3)

    assembled: list[str] = []
    next_line = 1
    for (start, end), content in sorted(chunks.items()):
        if start != next_line:
            raise AssertionError(
                f"app.js source coverage gap: expected line {next_line}, got {start}"
            )
        assembled.append(content)
        next_line = end + 1

    if next_line != AUDITED_FRONTEND_SOURCE_LINE_COUNT + 1:
        raise AssertionError(
            "app.js source coverage ended at "
            f"{next_line - 1}, expected {AUDITED_FRONTEND_SOURCE_LINE_COUNT}"
        )
    return "".join(assembled)


def original_runtime_after_audited_retirements() -> str:
    lines = (ORIGINAL_STATIC / "app.js").read_text(encoding="utf-8").splitlines(
        keepends=True
    )
    retired = {
        line_number
        for start, end in RETIRED_FRONTEND_SOURCE_RANGES
        for line_number in range(start, end + 1)
    }
    return "".join(
        line for line_number, line in enumerate(lines, start=1) if line_number not in retired
    )


def assert_frontend_runtime_matches_audited_baseline(testcase) -> None:
    testcase.assertEqual(
        reassembled_frontend_runtime(),
        original_runtime_after_audited_retirements(),
    )


def assert_moved_asset_matches(
    testcase,
    original_relative: str,
    frontend_relative: str | None = None,
) -> None:
    target_relative = frontend_relative or original_relative
    testcase.assertEqual(
        sha256(FRONTEND_ROOT / target_relative),
        sha256(ORIGINAL_STATIC / original_relative),
        original_relative,
    )


def assert_page_prefix_matches(testcase, page_relative: str) -> None:
    original = (ORIGINAL_STATIC / page_relative).read_text(encoding="utf-8")
    migrated = (FRONTEND_ROOT / page_relative).read_text(encoding="utf-8")
    testcase.assertTrue(
        migrated.startswith(original.rstrip("\n") + "\n\n"),
        page_relative,
    )