#!/usr/bin/env python3
from __future__ import annotations

import re
import subprocess
from datetime import datetime, timezone
from pathlib import Path

ROOT_DIR = Path(__file__).resolve().parents[2]
BACKLOG_PATH = ROOT_DIR / "BACKLOG.md"
ARCHIVE_PATH = ROOT_DIR / "ARCHIVE.md"
PROOF_PATH = ROOT_DIR / "PROOF.md"
IMPLEMENTATION_PATH = ROOT_DIR / "IMPLEMENTATION.md"
RESEARCH_ACTIVE_PATH = ROOT_DIR / "research/ACTIVE.md"
IMPLEMENTATION_ARCHIVE_DIR = ROOT_DIR / "archive/implementation"
RESEARCH_ARCHIVE_DIR = ROOT_DIR / "archive/research"

LANE_PREFIX = {
    "implementation": "I",
    "research": "R",
    "ops": "O",
    "bug": "B",
}

BACKLOG_SECTION = {
    "implementation": "## Implementation Candidates",
    "research": "## Research Candidates",
    "ops": "## Ops Candidates",
    "bug": "## Bugs",
}

ARCHIVE_SECTION = {
    "implementation": "## Implementation Turns",
    "research": "## Research Turns",
    "planning": "## Planning Events",
}


def now_utc() -> datetime:
    return datetime.now(timezone.utc)


def today_iso() -> str:
    return now_utc().date().isoformat()


def timestamp_slug() -> str:
    return now_utc().strftime("%Y%m%dT%H%M%SZ")


def slugify(value: str) -> str:
    slug = re.sub(r"[^a-z0-9]+", "-", value.lower()).strip("-")
    return slug or "turn"


def load_text(path: Path) -> str:
    return path.read_text(encoding="utf-8")


def save_text(path: Path, content: str) -> None:
    path.write_text(content.rstrip() + "\n", encoding="utf-8")


def insert_into_section(document: str, heading: str, block: str) -> str:
    lines = document.splitlines()
    try:
        start = lines.index(heading)
    except ValueError as exc:
        raise SystemExit(f"heading not found: {heading}") from exc

    end = len(lines)
    for idx in range(start + 1, len(lines)):
        if lines[idx].startswith("## "):
            end = idx
            break

    insert_at = end
    return "\n".join(lines[:insert_at] + [block] + lines[insert_at:]) + "\n"


def append_archive_line(section: str, line: str) -> None:
    content = load_text(ARCHIVE_PATH)
    updated = insert_into_section(content, ARCHIVE_SECTION[section], line)
    save_text(ARCHIVE_PATH, updated)


def read_backlog_lines() -> list[str]:
    return load_text(BACKLOG_PATH).splitlines()


def write_backlog_lines(lines: list[str]) -> None:
    save_text(BACKLOG_PATH, "\n".join(lines))


def next_backlog_id(lane: str) -> str:
    prefix = LANE_PREFIX[lane]
    pattern = re.compile(rf"\[{re.escape(prefix)}(\d+)\]")
    highest = 0
    for line in read_backlog_lines():
        match = pattern.search(line)
        if match:
            highest = max(highest, int(match.group(1)))
    return f"{prefix}{highest + 1:03d}"


def backlog_entry_map() -> dict[str, str]:
    entries: dict[str, str] = {}
    pattern = re.compile(r"- \[([A-Z]\d+)\] (.+)")
    for line in read_backlog_lines():
        match = pattern.match(line)
        if match:
            entries[match.group(1)] = match.group(2)
    return entries


def remove_backlog_ids(ids: list[str]) -> None:
    id_set = set(ids)
    pattern = re.compile(r"- \[([A-Z]\d+)\] ")
    kept: list[str] = []
    for line in read_backlog_lines():
        match = pattern.match(line)
        if match and match.group(1) in id_set:
            continue
        kept.append(line)
    write_backlog_lines(kept)


def git_has_changes() -> bool:
    result = subprocess.run(
        ["git", "-C", str(ROOT_DIR), "status", "--porcelain"],
        check=True,
        capture_output=True,
        text=True,
    )
    return bool(result.stdout.strip())


def path_has_changes(paths: list[Path]) -> bool:
    rel_paths = [str(path.relative_to(ROOT_DIR)) for path in paths]
    result = subprocess.run(
        ["git", "-C", str(ROOT_DIR), "status", "--porcelain", "--", *rel_paths],
        check=True,
        capture_output=True,
        text=True,
    )
    return bool(result.stdout.strip())


def git_commit(message: str, paths: list[Path]) -> None:
    if not path_has_changes(paths):
        return
    rel_paths = [str(path.relative_to(ROOT_DIR)) for path in paths]
    subprocess.run(["git", "-C", str(ROOT_DIR), "add", "--", *rel_paths], check=True)
    subprocess.run(["git", "-C", str(ROOT_DIR), "commit", "-m", message], check=True)