"""Internal tool to update the CHANGELOG."""

import json
import subprocess
import urllib.request
from dataclasses import dataclass
from datetime import datetime, timezone

GH_ORG = "py-pdf"
GH_PROJECT = "pypdf"
VERSION_FILE_PATH = "pypdf/_version.py"
CHANGELOG_FILE_PATH = "CHANGELOG.md"


@dataclass(frozen=True)
class Change:
    """Capture the data of a git commit."""

    commit_hash: str
    prefix: str
    message: str
    author: str
    author_login: str


def main(changelog_path: str) -> None:
    """
    Create a changelog.

    Args:
        changelog_path: The location of the CHANGELOG file

    """
    changelog = get_changelog(changelog_path)
    git_tag = get_most_recent_git_tag()
    changes, changes_with_author = get_formatted_changes(git_tag)
    if changes == "":
        print("No changes")
        return

    new_version = version_bump(git_tag, changes)
    new_version = get_version_interactive(new_version, changes)
    adjust_version_py(new_version)

    today = datetime.now(tz=timezone.utc)
    header = f"## Version {new_version}, {today:%Y-%m-%d}\n"
    url = f"https://github.com/{GH_ORG}/{GH_PROJECT}/compare/{git_tag}...{new_version}"
    trailer = f"\n[Full Changelog]({url})\n\n"
    new_entry = header + changes + trailer
    print(new_entry)
    write_commit_msg_file(new_version, changes_with_author + trailer)
    # write_release_msg_file(new_version, changes_with_author + trailer, today)

    # Make the script idempotent by checking if the new entry is already in the changelog
    if new_entry in changelog:
        print("Changelog is already up-to-date!")
        return

    new_changelog = "# CHANGELOG\n\n" + new_entry + strip_header(changelog)
    write_changelog(new_changelog, changelog_path)
    print_instructions(new_version)


def print_instructions(new_version: str) -> None:
    """Print release instructions."""
    print("=" * 80)
    print(f"☑  {VERSION_FILE_PATH} was adjusted to '{new_version}'")
    print(f"☑  {CHANGELOG_FILE_PATH} was adjusted")
    print()
    print("Now run:")
    print("  git commit -eF RELEASE_COMMIT_MSG.md")
    print("  git push")


def adjust_version_py(version: str) -> None:
    """Adjust the __version__ string."""
    with open(VERSION_FILE_PATH, "w") as fp:
        fp.write(f'__version__ = "{version}"\n')


def get_version_interactive(new_version: str, changes: str) -> str:
    """Get the new __version__ interactively."""
    from rich.prompt import Prompt  # noqa: PLC0415

    print("The changes are:")
    print(changes)
    orig = new_version
    new_version = Prompt.ask("New semantic version", default=orig)
    while not is_semantic_version(new_version):
        new_version = Prompt.ask(
            "That was not a semantic version. Please enter a semantic version",
            default=orig,
        )
    return new_version


def is_semantic_version(version: str) -> bool:
    """Check if the given version is a semantic version."""
    # This doesn't cover the edge-cases like pre-releases
    if version.count(".") != 2:
        return False
    try:
        return bool([int(part) for part in version.split(".")])
    except Exception:
        return False


def write_commit_msg_file(new_version: str, commit_changes: str) -> None:
    """
    Write a file that can be used as a commit message.

    Like this:

        git commit -eF RELEASE_COMMIT_MSG.md && git push
    """
    with open("RELEASE_COMMIT_MSG.md", "w") as fp:
        fp.write(f"REL: {new_version}\n\n")
        fp.write("## What's new\n")
        fp.write(commit_changes)


def write_release_msg_file(
    new_version: str, commit_changes: str, today: datetime
) -> None:
    """
    Write a file that can be used as a git tag message.

    Like this:

        git tag -eF RELEASE_TAG_MSG.md && git push
    """
    with open("RELEASE_TAG_MSG.md", "w") as fp:
        fp.write(f"Version {new_version}, {today:%Y-%m-%d}\n\n")
        fp.write("## What's new\n")
        fp.write(commit_changes)


def strip_header(md: str) -> str:
    """Remove the 'CHANGELOG' header."""
    return md.removeprefix("# CHANGELOG").lstrip()


def version_bump(git_tag: str, changes: str = "") -> str:
    """
    Increase the version of the git tag according to the release policy.

    The patch version is increased for regular changes and the minor version
    for enhancements or deprecations, which are the ``ENH`` and ``DEP``
    sections of the formatted changes. Major bumps stay manual.

    Args:
        git_tag: Old version tag
        changes: The formatted changes, as returned by
            :func:`get_formatted_changes`. When empty, a patch bump is assumed.

    Returns:
        The new version.

    """
    major, minor, patch = git_tag.split(".")
    if has_minor_changes(changes):
        return f"{major}.{int(minor) + 1}.0"
    return f"{major}.{minor}.{int(patch) + 1}"


def has_minor_changes(changes: str) -> bool:
    """
    Report whether the changes warrant a minor version bump.

    Args:
        changes: The formatted changes, as returned by
            :func:`get_formatted_changes`.

    Returns:
        Whether an enhancement or deprecation section is present.

    """
    return any(
        f"({prefix})" in line
        for line in changes.splitlines()
        if line.startswith("### ")
        for prefix in ("ENH", "DEP")
    )


def get_changelog(changelog_path: str) -> str:
    """
    Read the changelog.

    Args:
        changelog_path: Path to the CHANGELOG file

    Returns:
        Data of the CHANGELOG

    """
    with open(changelog_path, encoding="utf-8") as fh:
        return fh.read()


def write_changelog(new_changelog: str, changelog_path: str) -> None:
    """
    Write the changelog.

    Args:
        new_changelog: Contents of the new CHANGELOG
        changelog_path: Path where the CHANGELOG file is

    """
    with open(changelog_path, "w", encoding="utf-8") as fh:
        fh.write(new_changelog)


def get_formatted_changes(git_tag: str) -> tuple[str, str]:
    """
    Format the changes done since the last tag.

    Args:
        git_tag: the reference tag

    Returns:
        Changes done since git_tag

    """
    commits = get_git_commits_since_tag(git_tag)

    # Group by prefix
    grouped: dict[str, list[Change]] = {}
    for commit in commits:
        if commit.prefix not in grouped:
            grouped[commit.prefix] = []
        grouped[commit.prefix].append(
            commit
        )

    # Order prefixes
    order = [
        "SEC",
        "DEP",
        "ENH",
        "PI",
        "BUG",
        "ROB",
        "DOC",
        "DEV",
        "CI",
        "MAINT",
        "TST",
        "STY",
    ]
    abbrev2long = {
        "SEC": "Security",
        "DEP": "Deprecations",
        "ENH": "New Features",
        "BUG": "Bug Fixes",
        "ROB": "Robustness",
        "DOC": "Documentation",
        "DEV": "Developer Experience",
        "CI": "Continuous Integration",
        "MAINT": "Maintenance",
        "TST": "Testing",
        "STY": "Code Style",
        "PI": "Performance Improvements",
    }

    # Create output
    output = ""
    output_with_user = ""
    for prefix in order:
        if prefix not in grouped:
            continue
        tmp = f"\n### {abbrev2long[prefix]} ({prefix})\n"  # header
        output += tmp
        output_with_user += tmp
        for commit in grouped[prefix]:
            output += f"- {commit.message}\n"
            output_with_user += f"- {commit.message} by @{commit.author_login}\n"
        del grouped[prefix]

    if grouped:
        output += "\n### Other\n"
        output_with_user += "\n### Other\n"
        for prefix, commits in grouped.items():
            for commit in commits:
                output += f"- {prefix}: {commit.message}\n"
                output_with_user += (
                    f"- {prefix}: {commit.message} by @{commit.author_login}\n"
                )

    return output, output_with_user


def get_most_recent_git_tag() -> str:
    """
    Get the git tag most recently created.

    Returns:
        Most recently created git tag.

    """
    return subprocess.check_output(
        ["git", "describe", "--tag", "--abbrev=0"], stderr=subprocess.STDOUT, text=True
    ).strip()


def get_author_mapping(line_count: int) -> dict[str, str]:
    """
    Get the authors for each commit.

    Args:
        line_count: Number of lines from Git log output. Used for determining how
            many commits to fetch.

    Returns:
        A mapping of long commit hashes to author login handles.

    """
    per_page = min(line_count, 100)
    page = 1
    mapping: dict[str, str] = {}
    for _ in range(0, line_count, per_page):
        with urllib.request.urlopen(
            f"https://api.github.com/repos/{GH_ORG}/{GH_PROJECT}/commits?per_page={per_page}&page={page}"
        ) as response:
            commits = json.loads(response.read())
        page += 1
        for commit in commits:
            mapping[commit["sha"]] = commit["author"]["login"]
    return mapping


def get_git_commits_since_tag(git_tag: str) -> list[Change]:
    """
    Get all commits since the last tag.

    Args:
        git_tag: Reference tag from which the changes to the current commit are
            fetched.

    Returns:
        List of all changes since git_tag.

    """
    commits = (
        subprocess.check_output(
            [
                "git",
                "--no-pager",
                "log",
                f"{git_tag}..HEAD",
                '--pretty=format:"%H:::%s:::%aN"',
            ],
            stderr=subprocess.STDOUT,
        )
        .decode("UTF-8")
        .strip()
    )
    lines = commits.splitlines()
    authors = get_author_mapping(len(lines))
    return [parse_commit_line(line, authors) for line in lines if line != ""]


def parse_commit_line(line: str, authors: dict[str, str]) -> Change:
    """
    Parse the first line of a git commit message.

    Args:
        line: The first line of a git commit message.

    Returns:
        The parsed Change object

    Raises:
        ValueError: The commit line is not well-structured

    """
    parts = line.strip().strip('"\\').split(":::")
    if len(parts) != 3:
        raise ValueError(f"Invalid commit line: '{line}'")
    commit_hash, rest, author = parts
    if ":" in rest:
        prefix, message = rest.split(": ", 1)
    else:
        prefix = ""
        message = rest

    # Standardize
    message = message.strip()
    commit_hash = commit_hash.strip()

    author_login = authors[commit_hash]

    prefix = prefix.strip()
    if prefix == "DOCS":
        prefix = "DOC"

    return Change(
        commit_hash=commit_hash,
        prefix=prefix,
        message=message,
        author=author,
        author_login=author_login,
    )


if __name__ == "__main__":
    main(CHANGELOG_FILE_PATH)
