feat: add prediction and omit empty Buy/Sell

internal/archive/archive.go

@@ -67,22 +67,35 @@ func Save(cfg config.ArchiveConfig, run Run, now time.Time) (string, error) {
 	return dir, nil
 }
 
-// LoadLatest reads back the most recent previously-archived run's
-// report.md, for the prompt to dedup the next briefing against. Returns
-// ("", nil) if no prior run exists yet (e.g. first-ever run) — callers
-// should treat that as "no previous report" rather than an error.
-func LoadLatest(cfg config.ArchiveConfig) (string, error) {
+// RecentRun is one previously-archived run's timestamp and report text, as
+// returned by LoadRecent.
+type RecentRun struct {
+	When   time.Time
+	Report string
+}
+
+// runDirLayout is the timestamp format run directories are named with (see
+// Save), used by LoadRecent to recover each run's time.
+const runDirLayout = "20060102T150405Z"
+
+// LoadRecent reads back up to the last n previously-archived runs' report.md
+// contents, oldest first, for the prompt to dedup the next briefing against
+// a rolling window of recent history. Returns (nil, nil) if no prior run
+// exists yet (e.g. first-ever run) — callers should treat that as "no
+// previous reports" rather than an error. Runs whose report.md is missing or
+// unreadable are skipped rather than failing the whole call.
+func LoadRecent(cfg config.ArchiveConfig, n int) ([]RecentRun, error) {
 	base, err := resolveDir(cfg)
 	if err != nil {
-		return "", err
+		return nil, err
 	}
 
 	entries, err := os.ReadDir(base)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return "", nil
+			return nil, nil
 		}
-		return "", fmt.Errorf("archive: list %q: %w", base, err)
+		return nil, fmt.Errorf("archive: list %q: %w", base, err)
 	}
 
 	var runDirs []string
@@ -92,19 +105,27 @@ func LoadLatest(cfg config.ArchiveConfig) (string, error) {
 		}
 	}
 	if len(runDirs) == 0 {
-		return "", nil
+		return nil, nil
 	}
 	sort.Strings(runDirs) // timestamp-named dirs sort chronologically
-	latest := runDirs[len(runDirs)-1]
 
-	data, err := os.ReadFile(filepath.Join(base, latest, "report.md"))
-	if err != nil {
-		if os.IsNotExist(err) {
-			return "", nil
-		}
-		return "", fmt.Errorf("archive: read previous report: %w", err)
+	if len(runDirs) > n {
+		runDirs = runDirs[len(runDirs)-n:]
 	}
-	return string(data), nil
+
+	var runs []RecentRun
+	for _, name := range runDirs {
+		when, err := time.Parse(runDirLayout, name)
+		if err != nil {
+			continue
+		}
+		data, err := os.ReadFile(filepath.Join(base, name, "report.md"))
+		if err != nil {
+			continue
+		}
+		runs = append(runs, RecentRun{When: when.UTC(), Report: string(data)})
+	}
+	return runs, nil
 }
 
 // resolveDir returns cfg.Dir (or defaultDir if empty) with "~" expanded.