#!/usr/bin/env python3
"""Run selected numbered testcases through the IR backend and IRCompiler."""

from __future__ import annotations

import argparse
import subprocess
import sys
from dataclasses import dataclass
from pathlib import Path


@dataclass(frozen=True)
class ExpectedOutput:
    stdout: bytes
    returncode: int


@dataclass(frozen=True)
class Testcase:
    number: int
    source: Path
    input_file: Path | None
    output_file: Path | None


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description=(
            "Run numbered testcases like 1-5,7 with "
            "`cargo run -- -I -S -D -o output.ir testcase.c`, then "
            "`tools/IRCompiler -R output.ir`, and compare with testcase.out."
        )
    )
    parser.add_argument("numbers", help="testcase numbers, for example: 1-5,7")
    parser.add_argument(
        "--testcases",
        type=Path,
        default=Path("testcases"),
        help="testcase directory (default: testcases)",
    )
    parser.add_argument(
        "--ir",
        type=Path,
        default=Path("output.ir"),
        help="IR output path reused for each testcase (default: output.ir)",
    )
    parser.add_argument(
        "--ircompiler",
        type=Path,
        default=Path("tools/IRCompiler"),
        help="IRCompiler path (default: tools/IRCompiler)",
    )
    parser.add_argument(
        "-v",
        "--verbose",
        action="store_true",
        help="print compiler/interpreter stderr for passing cases too",
    )
    return parser.parse_args()


def parse_numbers(spec: str) -> list[int]:
    numbers: list[int] = []
    seen: set[int] = set()

    for raw_part in spec.split(","):
        part = raw_part.strip()
        if not part:
            continue

        if "-" in part:
            bounds = part.split("-", 1)
            if len(bounds) != 2 or not bounds[0] or not bounds[1]:
                raise ValueError(f"invalid range: {part!r}")
            start, end = int(bounds[0]), int(bounds[1])
            step = 1 if start <= end else -1
            values = range(start, end + step, step)
        else:
            values = (int(part),)

        for value in values:
            if value <= 0:
                raise ValueError(f"testcase number must be positive: {value}")
            if value not in seen:
                seen.add(value)
                numbers.append(value)

    if not numbers:
        raise ValueError("no testcase numbers specified")
    return numbers


def find_testcase(testcases_dir: Path, number: int) -> Testcase:
    prefix = f"{number:03d}_"
    matches = sorted(testcases_dir.glob(f"{prefix}*.c"))
    if not matches:
        raise FileNotFoundError(f"no C testcase found for {number} ({prefix}*.c)")
    if len(matches) > 1:
        joined = ", ".join(str(path) for path in matches)
        raise RuntimeError(f"multiple C testcases found for {number}: {joined}")

    source = matches[0]
    stem = source.with_suffix("")
    input_file = stem.with_suffix(".in")
    output_file = stem.with_suffix(".out")
    return Testcase(
        number=number,
        source=source,
        input_file=input_file if input_file.is_file() else None,
        output_file=output_file if output_file.is_file() else None,
    )


def parse_expected(output_file: Path) -> ExpectedOutput:
    data = output_file.read_bytes()
    lines = data.splitlines(keepends=True)
    if not lines:
        raise ValueError(f"empty expected output file: {output_file}")

    returncode_line = lines[-1].strip()
    try:
        returncode = int(returncode_line)
    except ValueError as err:
        raise ValueError(
            f"last line of {output_file} is not an integer return code: "
            f"{returncode_line!r}"
        ) from err

    return ExpectedOutput(stdout=b"".join(lines[:-1]), returncode=returncode)


def normalize_returncode(returncode: int) -> int:
    return returncode & 255


def strip_trailing_newlines(data: bytes) -> bytes:
    return data.rstrip(b"\r\n")


def run_command(
    command: list[str],
    *,
    stdin: bytes | None = None,
) -> subprocess.CompletedProcess[bytes]:
    return subprocess.run(
        command,
        input=stdin,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        check=False,
    )


def format_bytes(data: bytes) -> str:
    if not data:
        return "<empty>"
    try:
        return data.decode()
    except UnicodeDecodeError:
        return repr(data)


def format_bytes_debug(data: bytes) -> str:
    return f"{data!r} ({len(data)} bytes)"


def print_failure_detail(
    testcase: Testcase,
    *,
    expected: ExpectedOutput | None,
    actual_stdout: bytes,
    actual_returncode: int | None,
    stderr: bytes,
    verbose: bool,
) -> None:
    print(f"  source: {testcase.source}")
    if testcase.input_file is not None:
        print(f"  input:  {testcase.input_file}")
    if expected is not None:
        print("  expected stdout:")
        print(format_bytes(expected.stdout), end="" if expected.stdout.endswith(b"\n") else "\n")
        print(f"  expected stdout bytes: {format_bytes_debug(expected.stdout)}")
        print(f"  expected returncode: {expected.returncode}")
    print("  actual stdout:")
    print(format_bytes(actual_stdout), end="" if actual_stdout.endswith(b"\n") else "\n")
    print(f"  actual stdout bytes:   {format_bytes_debug(actual_stdout)}")
    if actual_returncode is not None:
        print(f"  actual returncode:   {actual_returncode}")
    if stderr and (verbose or expected is None):
        print("  stderr:")
        print(format_bytes(stderr), end="" if stderr.endswith(b"\n") else "\n")


def run_testcase(
    testcase: Testcase,
    *,
    ir_file: Path,
    ircompiler: Path,
    verbose: bool,
) -> bool:
    compile_cmd = [
        "cargo",
        "run",
        "--",
        "-I",
        "-S",
        "-D",
        "-o",
        str(ir_file),
        str(testcase.source),
    ]
    compile_result = run_command(compile_cmd)
    if compile_result.returncode != 0:
        print(f"[FAIL] {testcase.number:03d} compile failed")
        print_failure_detail(
            testcase,
            expected=None,
            actual_stdout=compile_result.stdout,
            actual_returncode=compile_result.returncode,
            stderr=compile_result.stderr,
            verbose=True,
        )
        return False

    stdin = testcase.input_file.read_bytes() if testcase.input_file is not None else None
    run_result = run_command([str(ircompiler), "-R", str(ir_file)], stdin=stdin)

    if testcase.output_file is None:
        print(f"[SKIP] {testcase.number:03d} missing .out: {testcase.source.name}")
        print_failure_detail(
            testcase,
            expected=None,
            actual_stdout=run_result.stdout,
            actual_returncode=run_result.returncode,
            stderr=run_result.stderr,
            verbose=verbose,
        )
        return False

    expected = parse_expected(testcase.output_file)
    actual_returncode = normalize_returncode(run_result.returncode)
    ok = (
        strip_trailing_newlines(run_result.stdout)
        == strip_trailing_newlines(expected.stdout)
        and actual_returncode == expected.returncode
    )

    status = "PASS" if ok else "FAIL"
    print(f"[{status}] {testcase.number:03d} {testcase.source.name}")
    if not ok or (verbose and (compile_result.stderr or run_result.stderr)):
        if verbose and compile_result.stderr:
            print("  compiler stderr:")
            print(
                format_bytes(compile_result.stderr),
                end="" if compile_result.stderr.endswith(b"\n") else "\n",
            )
        print_failure_detail(
            testcase,
            expected=expected,
            actual_stdout=run_result.stdout,
            actual_returncode=actual_returncode,
            stderr=run_result.stderr,
            verbose=verbose,
        )
    return ok


def main() -> int:
    args = parse_args()

    try:
        numbers = parse_numbers(args.numbers)
        testcases = [find_testcase(args.testcases, number) for number in numbers]
    except (OSError, RuntimeError, ValueError) as err:
        print(f"error: {err}", file=sys.stderr)
        return 2

    passed = 0
    for testcase in testcases:
        try:
            if run_testcase(
                testcase,
                ir_file=args.ir,
                ircompiler=args.ircompiler,
                verbose=args.verbose,
            ):
                passed += 1
        except OSError as err:
            print(f"[FAIL] {testcase.number:03d} failed to run command: {err}")
        except ValueError as err:
            print(f"[FAIL] {testcase.number:03d} invalid expected output: {err}")

    total = len(testcases)
    failed = total - passed
    print(f"\nsummary: {passed}/{total} passed, {failed} failed")
    return 0 if failed == 0 else 1


if __name__ == "__main__":
    raise SystemExit(main())