#!/usr/bin/env python3
"""
migrate_cache.py

Migrate DiskCache caches from “old” in‐memory entries (bytes, mime) into
“new” on‐disk read=True entries so that Flask can send them via send_file(path).

Usage:
    python migrate_cache.py /path/to/filecache_audio \
                           /path/to/filecache_image \
                           /path/to/filecache_video \
                           /path/to/filecache_other
"""

import io
import sys
from diskcache import Cache

def migrate_cache(cache_path):
    """
    Walks every key in the cache at `cache_path`.  If the value is a tuple of
    (bytes, mime), re‐writes it via read=True so DiskCache stores it as a file.
    """
    print(f"➡ Migrating cache at {cache_path!r}")
    cache = Cache(cache_path)
    migrated = 0
    skipped  = 0

    # Iterate keys without loading everything into memory
    for key in cache.iterkeys():
        try:
            val = cache.get(key)
        except Exception as e:
            print(f"  [ERROR] key={key!r} get failed: {e}")
            continue

        # Detect old‐style entries: (bytes, mime)
        if (
            isinstance(val, tuple)
            and len(val) == 2
            and isinstance(val[0], (bytes, bytearray))
            and isinstance(val[1], str)
        ):
            data, mime = val
            buf = io.BytesIO(data)
            buf.seek(0)
            # Re‐store as an on‐disk file
            cache.set(key, buf, read=True)
            migrated += 1
        else:
            skipped += 1

    cache.close()
    print(f"   → Done: migrated={migrated}, skipped={skipped}\n")


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: migrate_cache.py <cache_dir1> [<cache_dir2> ...]")
        sys.exit(1)

    for directory in sys.argv[1:]:
        migrate_cache(directory)