package clipmon

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"
)

const maxLoggedText = 1 << 16 // ponytail: 64KB cap per clipboard text entry

type Writer struct {
	dir       string
	imagesDir string
	file      *os.File
	bucket    string
}

func NewWriter(dir string) (*Writer, error) {
	imagesDir := filepath.Join(dir, "images")
	if err := os.MkdirAll(imagesDir, 0o700); err != nil {
		return nil, err
	}
	return &Writer{dir: dir, imagesDir: imagesDir}, nil
}

func (w *Writer) Write(event Event) error {
	bucket := HourBucket(event.Time)
	if bucket != w.bucket {
		if err := w.rotate(bucket); err != nil {
			return err
		}
	}
	_, err := w.file.WriteString(formatLine(event))
	return err
}

func (w *Writer) SavePNG(data []byte) (string, error) {
	name, err := randomName(".png")
	if err != nil {
		return "", err
	}
	path := filepath.Join(w.imagesDir, name)
	if err := os.WriteFile(path, data, 0o600); err != nil {
		return "", fmt.Errorf("write image: %w", err)
	}
	return filepath.ToSlash(filepath.Join("images", name)), nil
}

func (w *Writer) rotate(bucket string) error {
	if w.file != nil {
		if err := w.file.Close(); err != nil {
			return err
		}
		w.file = nil
	}
	path := filepath.Join(w.dir, LogFilename(bucket))
	file, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o600)
	if err != nil {
		return err
	}
	w.file = file
	w.bucket = bucket
	return nil
}

func (w *Writer) Close() error {
	if w.file == nil {
		return nil
	}
	err := w.file.Close()
	w.file = nil
	w.bucket = ""
	return err
}

func TrimText(text string) string {
	if len(text) <= maxLoggedText {
		return text
	}
	return text[:maxLoggedText] + "\n...(truncated)"
}

func randomName(ext string) (string, error) {
	var buf [16]byte
	if _, err := rand.Read(buf[:]); err != nil {
		return "", err
	}
	if !strings.HasPrefix(ext, ".") {
		ext = "." + ext
	}
	return hex.EncodeToString(buf[:]) + ext, nil
}

func PruneOld(dir string, retentionDays int) error {
	if retentionDays <= 0 {
		return nil
	}
	cutoff := time.Now().AddDate(0, 0, -retentionDays)
	if err := pruneLogs(dir, cutoff); err != nil {
		return err
	}
	return pruneImages(filepath.Join(dir, "images"), cutoff)
}

func pruneLogs(dir string, cutoff time.Time) error {
	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return err
	}
	for _, entry := range entries {
		if entry.IsDir() || !ValidLogFilename(entry.Name()) {
			continue
		}
		info, err := entry.Info()
		if err != nil {
			continue
		}
		if info.ModTime().Before(cutoff) {
			_ = os.Remove(filepath.Join(dir, entry.Name()))
		}
	}
	return nil
}

func pruneImages(dir string, cutoff time.Time) error {
	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return err
	}
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}
		info, err := entry.Info()
		if err != nil {
			continue
		}
		if info.ModTime().Before(cutoff) {
			_ = os.Remove(filepath.Join(dir, entry.Name()))
		}
	}
	return nil
}