// NextNVR v0.2.1 — Storage retention cleaner
// Background ticker that purges recordings older than retention_days.
// Skips .part.mp4 files (in-progress recordings).
// Works with flat directory: /mnt/recordings/{cam-name}/{YYYY-MM-DD-HH-MM}.mp4
package main

import (
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// Cleaner manages the periodic purge of old recordings.
type Cleaner struct {
	config  StorageConfig
	stopCh  chan struct{}
	running bool
}

// NewCleaner creates a new retention cleaner.
func NewCleaner(cfg StorageConfig) *Cleaner {
	if cfg.CleanupIntervalMins <= 0 {
		cfg.CleanupIntervalMins = 60
	}
	return &Cleaner{
		config: cfg,
		stopCh: make(chan struct{}),
	}
}

// Start begins the periodic cleanup loop.
func (c *Cleaner) Start() {
	c.running = true
	interval := time.Duration(c.config.CleanupIntervalMins) * time.Minute

	log.Printf("cleaner: starting — retention=%d days, interval=%v, path=%s",
		c.config.RetentionDays, interval, c.config.RecordingsPath)

	// Run immediately on startup.
	go c.purge()

	ticker := time.NewTicker(interval)
	defer ticker.Stop()

	for {
		select {
		case <-c.stopCh:
			c.running = false
			log.Println("cleaner: stopped")
			return
		case <-ticker.C:
			go c.purge()
		}
	}
}

// Stop signals the cleaner to shutdown.
func (c *Cleaner) Stop() {
	close(c.stopCh)
}

// purge walks the recordings directory and deletes files older than retention_days.
// Skips *.part.mp4 files (currently being recorded or crashed mid-segment).
func (c *Cleaner) purge() {
	cutoff := time.Now().Add(-time.Duration(c.config.RetentionDays) * 24 * time.Hour)
	deleted := 0
	var freedBytes int64

	err := filepath.Walk(c.config.RecordingsPath, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			log.Printf("cleaner: walk error for %s: %v", path, err)
			return nil // skip unreadable paths
		}
		if info.IsDir() {
			return nil
		}

		// Skip in-progress recordings.
		if strings.HasSuffix(strings.ToLower(info.Name()), ".part.mp4") {
			// Also clean up orphaned .part files older than 1 hour
			// (crashed recordings that were never renamed).
			if time.Since(info.ModTime()) > 1*time.Hour {
				size := info.Size()
				if err := os.Remove(path); err == nil {
					deleted++
					freedBytes += size
					log.Printf("cleaner: removed orphaned .part file: %s", filepath.Base(path))
				}
			}
			return nil
		}

		// Only process .mp4 files.
		if !strings.HasSuffix(strings.ToLower(info.Name()), ".mp4") {
			return nil
		}

		// Delete if older than retention cutoff.
		if info.ModTime().Before(cutoff) {
			size := info.Size()
			if err := os.Remove(path); err != nil {
				log.Printf("cleaner: failed to remove %s: %v", path, err)
				return nil
			}
			deleted++
			freedBytes += size
		}
		return nil
	})

	if err != nil {
		log.Printf("cleaner: walk error: %v", err)
	}

	// Remove empty camera directories.
	c.pruneEmptyDirs(c.config.RecordingsPath)

	if deleted > 0 {
		log.Printf("cleaner: removed %d files, freed %s", deleted, formatBytes(freedBytes))
	}
}

// pruneEmptyDirs removes empty camera directories.
func (c *Cleaner) pruneEmptyDirs(root string) {
	entries, err := os.ReadDir(root)
	if err != nil {
		return
	}
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		dir := filepath.Join(root, entry.Name())
		contents, _ := os.ReadDir(dir)
		if len(contents) == 0 {
			os.Remove(dir)
		}
	}
}

// formatBytes returns a human-readable byte count.
func formatBytes(bytes int64) string {
	const unit = 1024
	if bytes < unit {
		return itoa(int(bytes)) + " B"
	}
	div, exp := int64(unit), 0
	for n := bytes / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	return itoa(int(float64(bytes)/float64(div)*10)/10) + " " + string("KMGTPE"[exp]) + "B"
}