#!/usr/bin/env python3
"""
Check code coverage for new lines in a git commit using gcovr
"""
import argparse
import subprocess
import json
import re
import sys
import os
from typing import Dict, Set, Tuple, List, Optional


def create_argument_parser() -> argparse.ArgumentParser:
    """Create argument parser"""
    parser = argparse.ArgumentParser(
        description="Check gcov coverage for new code in a git commit",
        formatter_class=argparse.RawDescriptionHelpFormatter,
    )

    parser.add_argument(
        "--commit",
        help="Git commit hash, reference (e.g. HEAD, HEAD~1) or range (base...head)",
        default="HEAD",
    )

    parser.add_argument(
        "--path",
        metavar="PATH",
        help=(
            "Analyze coverage for a single file or a directory (relative or absolute path). "
            "When specified, --commit is ignored."
        ),
    )

    parser.add_argument(
        "--fail-under",
        type=float,
        metavar="PERCENT",
        default=0,
        help="Fail if coverage is below this percentage (0-100), default: 0 (no failure)",
    )

    parser.add_argument(
        "--min-lines",
        type=int,
        metavar="N",
        default=0,
        help=(
            "Skip --fail-under enforcement when new coverable lines < N. "
            "Small patches produce noisy percentages; this avoids false positives. "
            "Default: 0 (always enforce)"
        ),
    )

    return parser


def run_git_command(args: List[str], cwd: str = ".") -> str:
    """Run git command and return output"""
    result = subprocess.run(
        ["git"] + args,
        capture_output=True,
        cwd=cwd,
        check=True,
        encoding="utf-8",
        errors="replace",
    )
    return result.stdout


def get_changed_lines(commit: str, root: str) -> Dict[str, Set[int]]:
    """
    Get changed lines in specified commit
    Returns: {file_path: {set of changed line numbers}}
    """
    diff_output = run_git_command(
        ["diff", f"{commit}^", commit, "--unified=0"], cwd=root
    )

    changed_lines: Dict[str, Set[int]] = {}
    current_file = None

    for line in diff_output.split("\n"):
        if line.startswith("+++ b/"):
            current_file = line[6:]
            if current_file not in changed_lines:
                changed_lines[current_file] = set()

        elif line.startswith("@@"):
            match = re.search(r"\+(\d+)(?:,(\d+))?", line)
            if match and current_file:
                start_line = int(match.group(1))
                count = int(match.group(2)) if match.group(2) else 1
                for lineno in range(start_line, start_line + count):
                    changed_lines[current_file].add(lineno)

    return changed_lines


def get_coverage_data(root: str) -> Dict[str, Dict[int, int]]:
    """
    Get coverage data using gcovr
    Returns: {rel_file_path: {line_number: execution_count}}
    Notes:
    - Only lines explicitly present in gcovr JSON are considered "coverable".
        Lines that are missing from the JSON (e.g. preprocessor directives like
        #include, comments, whitespace, or excluded lines) are treated as
        non-coverable and will be ignored by the uncovered check.
    Raises: subprocess.CalledProcessError if gcovr fails
    """
    cmd = [
        "gcovr",
        "--gcov-ignore-parse-errors",
        "--json",
        "-",
        "--root",
        root,
    ]

    result = subprocess.run(
        cmd,
        capture_output=True,
        text=True,
        cwd=root,
        check=False,  # Don't raise exception automatically
    )

    if result.returncode != 0:
        error_msg = f"gcovr command failed (exit code {result.returncode}):\n"
        if result.stderr:
            error_msg += f"Error output:\n{result.stderr}\n"
        if result.stdout:
            error_msg += f"Standard output:\n{result.stdout}\n"
        raise subprocess.CalledProcessError(
            result.returncode, cmd, result.stdout, result.stderr
        )

    coverage_json = json.loads(result.stdout)
    coverage_data: Dict[str, Dict[int, int]] = {}

    for file_info in coverage_json.get("files", []):
        # Normalize path to be relative to repo root with POSIX separators.
        filename = file_info["file"]
        rel = os.path.relpath(filename, root)
        rel = rel.replace(os.path.sep, "/")
        coverage_data[rel] = {}

        for line_info in file_info.get("lines", []):
            line_number = line_info.get("line_number")
            # Only consider lines explicitly listed by gcovr as coverable.
            # Some gcovr versions may include additional flags like
            # "gcovr/noncode" or "excluded"; we simply ignore such lines
            # by relying on their absence from the JSON or by requiring
            # a numeric execution count.
            if line_number is None:
                continue
            count = line_info.get("count")
            if isinstance(count, int):
                coverage_data[rel][line_number] = count

    return coverage_data


def check_commit_coverage(
    commit: str, root: str
) -> Tuple[int, int, List[Tuple[str, int]], int]:
    """
    Check coverage for a commit or range
    Returns: (covered_lines, total_new_lines, uncovered_lines, skipped_noncoverable)
    """

    if "..." in commit:
        # Handle range format (base...head)
        base, head = commit.split("...")
        # Get changes for each commit in the range
        commits = run_git_command(["rev-list", f"{base}...{head}"], cwd=root).split()
    else:
        # Handle single commit
        commits = [commit]

    print(f"Found {len(commits)} commits in range:")
    changed_lines = {}
    for c in commits:
        print(f"  {c}")
        cl = get_changed_lines(c, root)
        for f, lines in cl.items():
            if f not in changed_lines:
                changed_lines[f] = set()
            changed_lines[f].update(lines)

    print(f"Found changes in {len(changed_lines)} files (before filtering):")
    for filename, lines in sorted(changed_lines.items()):
        print(f"  {filename}: {len(lines)} lines changed")

    print("Getting coverage data...")
    coverage_data = get_coverage_data(root)

    # Normalize changed file paths to POSIX separators for matching.
    normalized_changed: Dict[str, Set[int]] = {
        f.replace(os.path.sep, "/"): lines for f, lines in changed_lines.items()
    }

    # If desired, we could additionally filter by the gcovr filter pattern.
    # However, by intersecting with coverage_data keys, we inherently ignore
    # files that are not part of coverage anyway.

    total_new_lines = 0  # total coverable new lines (per gcovr)
    covered_lines = 0
    uncovered_lines: List[Tuple[str, int]] = []
    skipped_noncoverable = 0  # changed lines that gcovr doesn't consider coverable

    # Build quick lookup for filenames present in coverage.
    coverage_files: Set[str] = set(coverage_data.keys())

    # Iterate changed files and intersect with gcovr-provided coverable lines.
    for filename, line_numbers in normalized_changed.items():
        if filename not in coverage_files:
            # Entire file has no coverable lines in gcovr output; skip all.
            skipped_noncoverable += len(line_numbers)
            continue

        file_coverage = coverage_data[filename]
        for lineno in line_numbers:
            if lineno not in file_coverage:
                skipped_noncoverable += 1
                continue

            total_new_lines += 1
            if file_coverage[lineno] > 0:
                covered_lines += 1
            else:
                uncovered_lines.append((filename, lineno))

    return covered_lines, total_new_lines, uncovered_lines, skipped_noncoverable


def check_path_coverage(path: str, root: str) -> Tuple[int, int, List[Tuple[str, int]]]:
    """
    Compute coverage for a specific file or directory.
    Returns: (covered_lines, total_coverable_lines, uncovered_lines)
    Notes:
    - Only lines reported by gcovr as coverable are counted toward totals.
    - If PATH is a directory, coverage is aggregated over all coverable files within it.
    - If PATH is a file, coverage is computed only for that file.
    """
    # Normalize input path
    abs_path = os.path.abspath(path)
    if not os.path.exists(abs_path):
        print(f"Error: The specified path does not exist: {abs_path}", file=sys.stderr)
        sys.exit(1)

    # Ensure we operate from repo root to construct relative POSIX paths
    root = os.path.abspath(root)

    # Build relative POSIX target(s)
    rel = os.path.relpath(abs_path, root)
    rel_posix = rel.replace(os.path.sep, "/")

    print("Getting coverage data...")
    coverage_data = get_coverage_data(root)

    covered = 0
    total = 0
    uncovered: List[Tuple[str, int]] = []

    if os.path.isdir(abs_path):
        # Directory scope: include all files under this directory
        scoped_files = {}
        for f, lines in coverage_data.items():
            # Convert both to absolute paths for comparison
            f_abs = os.path.abspath(os.path.join(root, f.replace("/", os.path.sep)))
            # If the common path of abs_path and f_abs is abs_path, f is under abs_path
            if os.path.commonpath([abs_path, f_abs]) == abs_path:
                scoped_files[f] = lines

        print(f"Found {len(scoped_files)} coverable file(s) under: {rel_posix}")
        for filename, line_map in sorted(scoped_files.items()):
            for lineno, count in line_map.items():
                total += 1
                if count > 0:
                    covered += 1
                else:
                    uncovered.append((filename, lineno))
    else:
        # File scope
        if rel_posix in coverage_data:
            line_map = coverage_data[rel_posix]
            print(f"Found coverable file: {rel_posix}")
            for lineno, count in line_map.items():
                total += 1
                if count > 0:
                    covered += 1
                else:
                    uncovered.append((rel_posix, lineno))
        else:
            print(
                f"Warning: No coverable lines found for '{rel_posix}' in gcovr output."
            )

    return covered, total, uncovered


def report_coverage(
    header: str,
    total: int,
    covered: int,
    uncovered: List[Tuple[str, int]],
    fail_under: float,
    *,
    total_label: str,
    skipped_noncoverable: Optional[int] = None,
    min_lines: int = 0,
) -> int:
    """
    Print a standardized coverage report and return exit code (0/1).

    - header: text to show in the report title (e.g., "commit <hash>", "'<path>'")
    - total_label: label to use for the total line count (e.g.,
      "New coverable lines (per gcovr)" for commit mode, or
      "Coverable lines (per gcovr)" for path mode)
    - skipped_noncoverable: when provided, prints the skipped non-coverable count
    - min_lines: when > 0, skip --fail-under enforcement if total < min_lines
    """

    title = f" Coverage analysis results for {header} "
    separator = "=" * len(title)
    print(f"\n{separator}\n{title}\n{separator}")
    print(f"{total_label}: {total}")
    print(f"Covered lines: {covered}")
    print(f"Uncovered lines: {len(uncovered)}")
    if skipped_noncoverable is not None:
        print(f"Skipped non-coverable changed lines: {skipped_noncoverable}")

    retval = 0
    if total > 0:
        coverage_percent = (covered / total) * 100
        print(f"Coverage: {coverage_percent:.2f}%")

        # Check if this patch is too small to enforce the threshold
        if min_lines > 0 and fail_under > 0 and total < min_lines:
            print(
                f"\nℹ Only {total} new coverable line(s) (< {min_lines}), "
                f"skipping --fail-under enforcement."
            )
        elif coverage_percent < fail_under:
            print(
                f"\n✗ Coverage {coverage_percent:.2f}% is below required {fail_under}%"
            )
            retval = 1

    if uncovered:
        print(
            "\nUncovered lines (explicitly reported by gcovr as coverable with 0 hits):"
        )
        for filename, lineno in sorted(uncovered):
            print(f"  {filename}:{lineno}")
    else:
        if total == 0:
            print("\nNo coverable lines found.")
        else:
            print(f"\n✓ Code coverage check passed!")

    return retval


def main() -> int:
    """Main entry point"""
    parser = create_argument_parser()
    args = parser.parse_args()

    try:
        script_dir = os.path.dirname(os.path.abspath(__file__))
        root = os.path.dirname(script_dir)
        os.chdir(root)
        print(f"Current working directory: {root}")

        if args.path:
            # Path mode: ignore commit, compute coverage for file/dir
            # --min-lines is not applied here since it targets patch (commit) mode.
            covered, total, uncovered = check_path_coverage(args.path, root)

            return report_coverage(
                header=f"'{args.path}'",
                total=total,
                covered=covered,
                uncovered=uncovered,
                fail_under=args.fail_under,
                total_label="Coverable lines (per gcovr)",
            )
        else:
            # Commit mode: default behavior
            covered, total, uncovered, skipped_noncoverable = check_commit_coverage(
                args.commit, root
            )

            return report_coverage(
                header=f"commit {args.commit}",
                total=total,
                covered=covered,
                uncovered=uncovered,
                fail_under=args.fail_under,
                total_label="New coverable lines (per gcovr)",
                skipped_noncoverable=skipped_noncoverable,
                min_lines=args.min_lines,
            )

    except subprocess.CalledProcessError as e:
        print(f"Error: Command failed - {e}", file=sys.stderr)
        if e.stderr:
            print(f"Error details:\n{e.stderr}", file=sys.stderr)
        if e.stdout:
            print(f"Command output:\n{e.stdout}", file=sys.stderr)
        return e.returncode
    except Exception as e:
        print(f"Error: {e}", file=sys.stderr)
        return 2


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