from __future__ import annotations

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,
)


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


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}"
            )
        if len(content.splitlines(keepends=True)) != end - start + 1:
            raise AssertionError(f"app.js line count changed in range {start}-{end}")
        assembled.append(content)
        next_line = end + 1

    original_line_count = len(
        (ORIGINAL_STATIC / "app.js").read_text(encoding="utf-8").splitlines()
    )
    if next_line != original_line_count + 1:
        raise AssertionError(
            f"app.js source coverage ended at {next_line - 1}, expected {original_line_count}"
        )
    return "".join(assembled)


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,
    )