fix: improve show command cache design and reliability

- Merge get_tweet_id_by_index + get_cache_size into resolve_cached_tweet
  to eliminate redundant file IO on cache miss
- Move save_tweet_cache before emit_structured so --json/--yaml modes
  also persist the cache for subsequent show commands
- Extract _print_show_hint helper to reduce duplication
- Add trailing newline to cache.py

twitter_cli/cache.py

@@ -6,7 +6,7 @@ import json
 import logging
 import time
 from pathlib import Path
-from typing import List, Optional
+from typing import List, Optional, Tuple
 
 from .models import Tweet
 
@@ -50,19 +50,17 @@ def _load_cache() -> Optional[List[dict]]:
         return None
 
 
-def get_tweet_id_by_index(index: int) -> Optional[str]:
+def resolve_cached_tweet(index: int) -> Tuple[Optional[str], int]:
-    """Return tweet ID at *index* (1-based), or None if not found."""
+    """Resolve a 1-based index to a tweet ID, returning (tweet_id, cache_size).
+
+    Returns (tweet_id, cache_size) where tweet_id is None if the index
+    cannot be resolved (empty/expired cache or out-of-range index).
+    """
     entries = _load_cache()
     if entries is None:
-        return None
+        return None, 0
     for entry in entries:
         if entry.get("index") == index:
             tweet_id = entry.get("id")
-            return str(tweet_id) if tweet_id is not None else None
+            return (str(tweet_id) if tweet_id is not None else None), len(entries)
-    return None
+    return None, len(entries)
-
-
-def get_cache_size() -> int:
-    """Return number of tweets in the current cache (0 if unavailable)."""
-    entries = _load_cache()
-    return len(entries) if entries is not None else 0

twitter_cli/cli.py

@@ -45,7 +45,7 @@ from rich.console import Console
 
 from . import __version__
 from .auth import get_cookies
-from .cache import get_cache_size, get_tweet_id_by_index, save_tweet_cache
+from .cache import resolve_cached_tweet, save_tweet_cache
 from .client import TwitterClient
 from .config import load_config
 from .filter import filter_tweets
@@ -349,17 +349,18 @@ def _fetch_and_display(fetch_fn, label, emoji, max_count, as_json, as_yaml, outp
         click.echo(tweets_to_compact_json(filtered))
         return
 
+    save_tweet_cache(filtered)
+
     if emit_structured(tweets_to_data(filtered), as_json=as_json, as_yaml=as_yaml):
         return
 
-    save_tweet_cache(filtered)
     print_tweet_table(
         filtered,
         console,
         title="%s %s — %d tweets" % (emoji, label, len(filtered)),
         full_text=full_text,
     )
-    console.print("[dim]💡 Use `twitter show <N>` to view tweet #N from this list.[/dim]")
+    _print_show_hint()
     console.print()
 
 
@@ -443,14 +444,15 @@ def feed(ctx, feed_type, max_count, as_json, as_yaml, input_file, output_file, d
         click.echo(tweets_to_compact_json(filtered))
         return
 
+    save_tweet_cache(filtered)
+
     if emit_structured(tweets_to_data(filtered), as_json=as_json, as_yaml=as_yaml):
         return
 
     title = "👥 Following" if feed_type == "following" else "📱 Twitter"
     title += " — %d tweets" % len(filtered)
-    save_tweet_cache(filtered)
     print_tweet_table(filtered, console, title=title, full_text=full_text)
-    console.print("[dim]💡 Use `twitter show <N>` to view tweet #N from this list.[/dim]")
+    _print_show_hint()
     console.print()
 
 
@@ -725,6 +727,12 @@ def _emit_tweet_detail(tweets, compact, as_json, as_yaml, full_text):
     console.print()
 
 
+def _print_show_hint():
+    # type: () -> None
+    """Print a hint about the `show` command."""
+    console.print("[dim]💡 Use `twitter show <N>` to view tweet #N from this list.[/dim]")
+
+
 @cli.command()
 @click.argument("index", type=click.IntRange(1))
 @click.option("--max", "-n", "max_count", type=int, default=None, help="Max replies to fetch.")
@@ -736,9 +744,8 @@ def show(ctx, index, max_count, full_text, as_json, as_yaml):
     """View tweet #INDEX from the last feed/search results."""
     compact = ctx.obj.get("compact", False)
 
-    tweet_id = get_tweet_id_by_index(index)
+    tweet_id, cache_size = resolve_cached_tweet(index)
     if tweet_id is None:
-        cache_size = get_cache_size()
         if cache_size == 0:
             raise click.UsageError(
                 "No cached results found. Run `twitter feed`, `twitter search`, "