#!/usr/bin/env python3
"""
CLI entry point: re-download mod files that have changed on the server.

Use this after you have updated mod files on the Caddy server without
changing the modlist structure (same mods, same Steam IDs, new file versions).

Detection method: compare local file sizes against server file sizes.
A file is considered stale when it is missing locally OR its local size
differs from the server-reported size.  Use --force to ignore size checks
and re-download every file unconditionally.

Usage:
    python update_mods.py                          # check all groups/mods
    python update_mods.py --group shared           # limit to one group
    python update_mods.py --mod @ace               # limit to one mod folder
    python update_mods.py --force                  # re-download everything
    python update_mods.py --force --group shared   # force-update one group
"""

from __future__ import annotations

import argparse
import sys

from tqdm import tqdm

from arma_modlist_tools.compat import fix_console_encoding
from arma_modlist_tools.config import load_config
from arma_modlist_tools.fetcher import (
    build_server_index, find_mod_folder,
    list_mod_files, list_mod_updates,
    download_file, make_session,
)

fix_console_encoding()


def _fmt_bytes(n: int) -> str:
    for unit in ("B", "KB", "MB", "GB"):
        if n < 1024:
            return f"{n:.1f} {unit}"
        n /= 1024
    return f"{n:.1f} TB"


def _collect_targets(cfg, group_filter: str | None, mod_filter: str | None) -> list[tuple[str, str, object]]:
    """
    Walk downloads/ and return (group, folder_name, folder_path) for each
    @Mod folder that passes the group/mod filters.
    """
    targets = []
    if not cfg.downloads.is_dir():
        return targets
    for group_dir in sorted(cfg.downloads.iterdir()):
        if not group_dir.is_dir():
            continue
        if group_filter and group_dir.name != group_filter:
            continue
        for mod_dir in sorted(group_dir.iterdir()):
            if not mod_dir.is_dir() or not mod_dir.name.startswith("@"):
                continue
            if mod_filter and mod_dir.name != mod_filter:
                continue
            targets.append((group_dir.name, mod_dir.name, mod_dir))
    return targets


def main() -> None:
    cfg = load_config()

    parser = argparse.ArgumentParser(
        description="Re-download mod files that have changed on the server."
    )
    parser.add_argument("--group", "-g", metavar="GROUP",
                        help="Only check mods in this group folder (e.g. shared)")
    parser.add_argument("--mod", "-m", metavar="MOD",
                        help="Only check this mod folder name (e.g. @ace)")
    parser.add_argument("--force", action="store_true",
                        help="Re-download all files regardless of size match")
    args = parser.parse_args()

    # ---- Collect local mod folders to check ----
    targets = _collect_targets(cfg, args.group, args.mod)
    if not targets:
        print("\nNo mod folders found matching the given filters.\n")
        sys.exit(0)

    # ---- Build server index ----
    print(f"\nBuilding server index...")
    index = build_server_index(cfg.server_url, cfg.server_auth)
    print(f"  {len(index['by_steam_id'])} mods indexed\n")

    session = make_session(cfg.server_auth)

    mode = "force" if args.force else "size-check"
    print(f"  Mode: {mode}")
    print(f"  Checking {len(targets)} mod folder(s)...\n")

    # Column widths for the summary table
    COL_MOD   = 44
    COL_GROUP = 24

    total_checked = total_updated = total_bytes = 0
    not_on_server = []

    for group, folder_name, mod_dir in targets:
        # Find this mod on the server by name (no steam_id available from local dir)
        mod_stub = {"name": folder_name, "steam_id": None}
        folder_url = find_mod_folder(mod_stub, index)

        if not folder_url:
            tqdm.write(f"  [?] {folder_name:<{COL_MOD}}  {group:<{COL_GROUP}}  not found on server")
            not_on_server.append(f"{group}/{folder_name}")
            continue

        # Determine which files need downloading
        if args.force:
            stale = list_mod_files(folder_url, session)
        else:
            stale = list_mod_updates(folder_url, mod_dir, session)

        all_files = list_mod_files(folder_url, session) if not args.force else stale
        checked = len(all_files) if not args.force else len(stale)

        if not stale:
            print(f"  [=] {folder_name:<{COL_MOD}}  {group:<{COL_GROUP}}  {checked} files  up-to-date")
            total_checked += checked
            continue

        # Download stale files
        mod_bytes = 0
        with tqdm(
            total=len(stale), unit="file",
            desc=f"  {folder_name[-COL_MOD:]:<{COL_MOD}}",
            position=0, leave=True, dynamic_ncols=True,
        ) as file_bar:
            for rel, url, size in stale:
                dest_file = mod_dir / rel
                with tqdm(
                    total=size if size else None,
                    unit="B", unit_scale=True, unit_divisor=1024,
                    desc=f"  {rel[-40:]:40s}",
                    position=1, leave=False, dynamic_ncols=True,
                ) as chunk_bar:
                    n = download_file(url, dest_file, session,
                                      on_chunk=lambda b: chunk_bar.update(b))
                mod_bytes += n
                file_bar.update(1)

        total_checked += checked
        total_updated += len(stale)
        total_bytes   += mod_bytes
        print(f"  [+] {folder_name:<{COL_MOD}}  {group:<{COL_GROUP}}  "
              f"{checked} files  {len(stale)} updated  ({_fmt_bytes(mod_bytes)})")

    print(f"\n{'='*56}")
    print(f"  Total: {total_checked} files checked, "
          f"{total_updated} updated, "
          f"{_fmt_bytes(total_bytes)} downloaded")
    if not_on_server:
        print(f"  Not found on server ({len(not_on_server)}): {', '.join(not_on_server)}")
    print(f"{'='*56}\n")

    if total_updated == 0 and not not_on_server:
        print("  All mods are up-to-date.\n")


if __name__ == "__main__":
    main()