#!/bin/env python3
#
# Based on check-style.py by
# Carlos Garnacho <carlosg@gnome.org>

import argparse
import os
import re
import subprocess
import sys
import tempfile

# Path relative to this script
uncrustify_cfg = ".gitlab-ci/uncrustify.cfg"


def run_diff(sha):
    proc = subprocess.run(
        ["git", "diff", "-U0", "--function-context", sha, "HEAD"],
        stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT,
        encoding="utf-8",
    )
    return proc.stdout.strip().splitlines()


def find_chunks(diff):
    file_entry_re = re.compile(r"^\+\+\+ b/(.*)$")
    diff_chunk_re = re.compile(r"^@@ -\d+,\d+ \+(\d+),(\d+)")
    file = None
    chunks = []

    for line in diff:
        match = file_entry_re.match(line)
        if match:
            file = match.group(1)

        match = diff_chunk_re.match(line)
        if match:
            start = int(match.group(1))
            len = int(match.group(2))
            end = start + len

            if len > 0 and (
                file.endswith(".c") or file.endswith(".h") or file.endswith(".vala")
            ):
                chunks.append({"file": file, "start": start, "end": end})

    return chunks


def reformat_chunks(chunks, rewrite, dry_run):
    # Creates temp file with INDENT-ON/OFF comments
    def create_temp_file(file, start, end):
        with open(file) as f:
            tmp = tempfile.NamedTemporaryFile()
            if start > 1:
                tmp.write(b"/** *INDENT-OFF* **/\n")
            for i, line in enumerate(f, start=1):
                if i == start - 1:
                    tmp.write(b"/** *INDENT-ON* **/\n")

                tmp.write(bytes(line, "utf-8"))
                if i == end - 1:
                    tmp.write(b"/** *INDENT-OFF* **/\n")
            tmp.seek(0)
        return tmp

    # Removes uncrustify INDENT-ON/OFF helper comments
    def remove_indent_comments(output):
        tmp = tempfile.NamedTemporaryFile()
        for line in output:
            if line != b"/** *INDENT-OFF* **/\n" and line != b"/** *INDENT-ON* **/\n":
                tmp.write(line)

        tmp.seek(0)
        return tmp

    changed = None
    for chunk in chunks:
        # Add INDENT-ON/OFF comments
        tmp = create_temp_file(chunk["file"], chunk["start"], chunk["end"])

        # uncrustify chunk
        proc = subprocess.run(
            ["uncrustify", "-c", uncrustify_cfg, "-f", tmp.name],
            stdout=subprocess.PIPE,
        )
        reindented = proc.stdout.splitlines(keepends=True)
        if proc.returncode != 0:
            continue

        tmp.close()

        # Remove INDENT-ON/OFF comments
        formatted = remove_indent_comments(reindented)

        if dry_run is True:
            # Show changes
            proc = subprocess.run(
                ["diff", "-up", "--color=always", chunk["file"], formatted.name],
                stdout=subprocess.PIPE,
                stderr=subprocess.STDOUT,
                encoding="utf-8",
            )
            diff = proc.stdout
            if diff != "":
                output = re.sub("\t", "↦\t", diff)
                print(output)
                changed = True
        else:
            # Apply changes
            diff = subprocess.run(
                ["diff", "-up", chunk["file"], formatted.name],
                stdout=subprocess.PIPE,
                stderr=subprocess.STDOUT,
            )
            subprocess.run(["patch", chunk["file"]], input=diff.stdout)

        formatted.close()

    return changed


def main(argv):
    parser = argparse.ArgumentParser(
        description="Check code style. Needs uncrustify installed."
    )
    parser.add_argument(
        "--sha", metavar="SHA", type=str, help="SHA for the commit to compare HEAD with"
    )
    parser.add_argument(
        "--dry-run",
        "-d",
        type=bool,
        action=argparse.BooleanOptionalAction,
        help="Only print changes to stdout, do not change code",
    )
    parser.add_argument(
        "--rewrite",
        "-r",
        type=bool,
        action=argparse.BooleanOptionalAction,
        help="Whether to amend the result to the last commit (e.g. 'git rebase --exec \"%(prog)s -r\"')",
    )

    if not os.path.exists(".git"):
        print("Not in toplevel of a git repository", fille=sys.stderr)
        return 1

    args = parser.parse_args(argv)
    sha = args.sha or "HEAD^"

    diff = run_diff(sha)
    chunks = find_chunks(diff)
    changed = reformat_chunks(chunks, args.rewrite, args.dry_run)

    if args.dry_run is not True and args.rewrite is True:
        proc = subprocess.run(["git", "add", "-p"])
        if proc.returncode == 0:
            # Commit the added changes as a squash commit
            subprocess.run(
                ["git", "commit", "--squash", "HEAD", "-C", "HEAD"],
                stdout=subprocess.DEVNULL,
            )
            # Delete the unapplied changes
            subprocess.run(["git", "reset", "--hard"], stdout=subprocess.DEVNULL)
            return 0
    elif args.dry_run is True and changed is True:
        print(
            f"""
Issue the following commands in your local tree to apply the suggested changes:

    $ git rebase {sha} --exec "./.gitlab-ci/check-style.py -r"
    $ git rebase --autosquash {sha}

Don't trust uncrustify unconditionally.
"""
        )
        return 1
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))