package audio

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/adapters/storage"
	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
)

// S3MaterializeRequest describes one S3-backed audio materialization.
type S3MaterializeRequest struct {
	Store        storage.ObjectStore
	Object       storage.ObjectInfo
	Bucket       string
	CacheRoot    string
	CacheEnabled bool
	SpoolPath    string
	DestPath     string
}

// S3MaterializeResult captures local materialization provenance.
type S3MaterializeResult struct {
	Checksum   string
	CachePath  string
	SpoolPath  string
	CacheHit   bool
	Downloaded bool
}

// MaterializeS3Audio installs one S3 audio object into the destination path,
// reusing and refreshing the durable local cache when enabled.
func MaterializeS3Audio(ctx context.Context, req S3MaterializeRequest) (S3MaterializeResult, error) {
	if err := ctx.Err(); err != nil {
		return S3MaterializeResult{}, err
	}
	if req.Store == nil {
		return S3MaterializeResult{}, fmt.Errorf("object store is required")
	}
	key := strings.TrimSpace(req.Object.Key)
	if key == "" {
		return S3MaterializeResult{}, fmt.Errorf("s3 object key is required")
	}
	if strings.TrimSpace(req.DestPath) == "" {
		return S3MaterializeResult{}, fmt.Errorf("destination path is required")
	}

	result := S3MaterializeResult{}
	if req.CacheEnabled {
		cachePath, err := artifacts.S3AudioCachePath(req.CacheRoot, req.Bucket, key)
		if err != nil {
			return S3MaterializeResult{}, fmt.Errorf("resolve audio cache path: %w", err)
		}
		result.CachePath = cachePath
		if ok, err := validCachedAudio(cachePath, req.Object.Size); err != nil {
			return S3MaterializeResult{}, err
		} else if ok {
			checksum, err := fileops.CopyFileAtomicWithChecksum(cachePath, req.DestPath, 0o644)
			if err != nil {
				return S3MaterializeResult{}, fmt.Errorf("materialize cached audio %q: %w", cachePath, err)
			}
			result.Checksum = checksum
			result.CacheHit = true
			return result, nil
		}
	}

	spoolPath := strings.TrimSpace(req.SpoolPath)
	if spoolPath == "" {
		return S3MaterializeResult{}, fmt.Errorf("spool path is required for s3 audio download")
	}
	if err := downloadObjectAtomic(ctx, req.Store, key, spoolPath); err != nil {
		return S3MaterializeResult{}, fmt.Errorf("download s3 audio object %q: %w", key, err)
	}
	if err := validateLocalAudio(spoolPath, req.Object.Size); err != nil {
		return S3MaterializeResult{}, fmt.Errorf("validate downloaded audio %q: %w", spoolPath, err)
	}

	checksum, err := fileops.CopyFileAtomicWithChecksum(spoolPath, req.DestPath, 0o644)
	if err != nil {
		return S3MaterializeResult{}, fmt.Errorf("materialize downloaded audio %q: %w", filepath.Base(req.DestPath), err)
	}
	result.Checksum = checksum
	result.SpoolPath = spoolPath
	result.Downloaded = true

	if result.CachePath != "" {
		if _, err := fileops.CopyFileAtomicWithChecksum(spoolPath, result.CachePath, 0o644); err != nil {
			return S3MaterializeResult{}, fmt.Errorf("populate audio cache %q: %w", result.CachePath, err)
		}
	}

	return result, nil
}

func validCachedAudio(path string, expectedSize int64) (bool, error) {
	info, err := os.Stat(path)
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, fmt.Errorf("stat cached audio %q: %w", path, err)
	}
	if info.IsDir() {
		return false, fmt.Errorf("cached audio path is a directory: %q", path)
	}
	if info.Size() <= 0 {
		return false, nil
	}
	if expectedSize > 0 && info.Size() != expectedSize {
		return false, nil
	}
	return true, nil
}

func validateLocalAudio(path string, expectedSize int64) error {
	info, err := os.Stat(path)
	if err != nil {
		return fmt.Errorf("stat: %w", err)
	}
	if info.IsDir() {
		return fmt.Errorf("path is a directory")
	}
	if info.Size() <= 0 {
		return fmt.Errorf("file is empty")
	}
	if expectedSize > 0 && info.Size() != expectedSize {
		return fmt.Errorf("size %d does not match remote size %d", info.Size(), expectedSize)
	}
	return nil
}

func downloadObjectAtomic(ctx context.Context, store storage.ObjectStore, key, destPath string) error {
	if strings.TrimSpace(destPath) == "" {
		return fmt.Errorf("destination path is required")
	}
	dir := filepath.Dir(destPath)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return fmt.Errorf("create destination directory: %w", err)
	}
	base := filepath.Base(destPath)
	tmp, err := os.CreateTemp(dir, "."+base+".download-*.tmp")
	if err != nil {
		return fmt.Errorf("create temp file: %w", err)
	}
	tmpPath := tmp.Name()
	if err := tmp.Close(); err != nil {
		_ = os.Remove(tmpPath)
		return fmt.Errorf("close temp file: %w", err)
	}
	removeTmp := true
	defer func() {
		if removeTmp {
			_ = os.Remove(tmpPath)
		}
	}()

	if err := store.Download(ctx, key, tmpPath); err != nil {
		return err
	}
	if err := fileops.InstallDownloadedTempFile(tmpPath, destPath, 0o644); err != nil {
		return err
	}
	removeTmp = false
	return nil
}