#!/usr/bin/env python3
"""
generate-compose.py
Reads .env and generates docker-compose.override.yml with NAS volumes.
No external dependencies required.
"""

import os
import sys
import re
from pathlib import Path

ENV_FILE = Path(".env")
OUTPUT_FILE = Path("docker-compose.override.yml")

OVERRIDE_HEADER = """\
# Auto-generated by generate-compose.py — do not edit manually.
# Re-run the script after changing NAS_* entries in .env.

services:
  backend:
    volumes:
"""


def load_env(path: Path) -> dict:
    env = {}
    if not path.exists():
        print(f"[ERROR] {path} not found. Copy .env.example to .env first.")
        sys.exit(1)
    with path.open(encoding="utf-8") as fh:
        for line in fh:
            line = line.strip()
            if not line or line.startswith("#"):
                continue
            if "=" not in line:
                continue
            key, _, value = line.partition("=")
            key = key.strip()
            # Strip inline comments
            value = value.split("#")[0].strip()
            env[key] = value
    return env


def parse_nas_entries(env: dict) -> list[tuple[str, str, str]]:
    """Return list of (key, name, host_path) sorted by key."""
    nas_pattern = re.compile(r"^NAS_(\d+)$")
    entries = []
    for key, value in env.items():
        match = nas_pattern.match(key)
        if not match:
            continue
        if "|" not in value:
            print(f"[WARN] {key}={value!r} — expected format 'Name|/host/path', skipping.")
            continue
        name, _, host_path = value.partition("|")
        entries.append((key, name.strip(), host_path.strip()))
    entries.sort(key=lambda t: int(t[0].split("_")[1]))
    return entries


def validate_paths(entries: list[tuple[str, str, str]]) -> None:
    for key, name, host_path in entries:
        if not Path(host_path).exists():
            print(f"[WARN] {key} — host path does not exist: {host_path!r}")
        else:
            print(f"[OK]   {key} — {name!r} → {host_path}")


def generate_override(entries: list[tuple[str, str, str]]) -> str:
    lines = [OVERRIDE_HEADER]
    for idx, (key, name, host_path) in enumerate(entries, start=1):
        container_path = f"/nas/nas{idx}"
        lines.append(f"      - {host_path}:{container_path}:ro  # {name}")
    # Pass NAS_X env vars into the container so config.py can read the names
    lines.append("    environment:")
    for idx, (key, name, host_path) in enumerate(entries, start=1):
        lines.append(f"      - {key}={name}|/nas/nas{idx}")
    lines.append("")
    return "\n".join(lines)


def main() -> None:
    print("=" * 55)
    print("  MediaTracker — generate-compose.py")
    print("=" * 55)

    env = load_env(ENV_FILE)
    entries = parse_nas_entries(env)

    if not entries:
        print("[ERROR] No NAS_* entries found in .env. Add at least one NAS.")
        sys.exit(1)

    print(f"\nFound {len(entries)} NAS source(s):\n")
    validate_paths(entries)

    content = generate_override(entries)
    OUTPUT_FILE.write_text(content, encoding="utf-8")

    print(f"\n[DONE] {OUTPUT_FILE} generated with {len(entries)} volume(s).")
    print("\nNext step:")
    print("  docker compose -f docker-compose.yml -f docker-compose.override.yml up -d --build\n")


if __name__ == "__main__":
    main()