package main

import (
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"os"
	"path/filepath"
)

const (
	voiceDirName  = "voices"
	voiceMaxBytes = 20 << 20
)

var errVoiceSize = errors.New("voice note is empty or exceeds 20 MB")

// VoiceStore holds immutable audio shared by all agents. Names are hashes of
// the received bytes, not sender filenames. The decoder detects the format.
type VoiceStore struct {
	dir string
}

// Save publishes private audio atomically before its message is acknowledged.
// Only nonempty input up to voiceMaxBytes is stored.
func (s *VoiceStore) Save(data []byte) (name string, err error) {
	if len(data) == 0 || len(data) > voiceMaxBytes {
		return "", errVoiceSize
	}

	sum := sha256.Sum256(data)
	name = hex.EncodeToString(sum[:]) + ".audio"
	err = os.MkdirAll(s.dir, 0o700)
	if err != nil {
		return "", fmt.Errorf("create voice directory: %w", err)
	}

	file, err := os.CreateTemp(s.dir, ".voice-*")
	if err != nil {
		return "", fmt.Errorf("create voice file: %w", err)
	}

	defer func() {
		err = errors.Join(err, os.Remove(file.Name()))
	}()

	_, err = file.Write(data)
	if err == nil {
		err = file.Sync()
	}

	err = errors.Join(err, file.Close())
	if err != nil {
		return "", fmt.Errorf("write voice: %w", err)
	}

	err = os.Link(file.Name(), filepath.Join(s.dir, name))
	if err != nil && !errors.Is(err, os.ErrExist) {
		return "", fmt.Errorf("publish voice: %w", err)
	}

	return name, nil
}