package server

import (
	"encoding/json"
	"fmt"
	"mime"
	"os"
	"path/filepath"
	"strings"
	"sync"

	"warpbox/lib/models"
)

var boxManifestMu sync.Mutex

func listBoxFiles(boxID string) ([]models.BoxFile, error) {
	if manifest, err := reconcileBoxManifest(boxID); err == nil && len(manifest.Files) > 0 {
		files := make([]models.BoxFile, 0, len(manifest.Files))
		for _, file := range manifest.Files {
			files = append(files, decorateBoxFile(boxID, file))
		}

		return files, nil
	}

	return listCompletedFilesFromDisk(boxID)
}

func reconcileBoxManifest(boxID string) (models.BoxManifest, error) {
	boxManifestMu.Lock()
	defer boxManifestMu.Unlock()

	manifest, err := readBoxManifestUnlocked(boxID)
	if err != nil {
		return manifest, err
	}

	changed := false
	for index, file := range manifest.Files {
		path := filepath.Join(boxPath(boxID), file.Name)
		info, err := os.Stat(path)
		if err != nil {
			continue
		}

		if file.Status == fileStatusReady && file.Size == info.Size() {
			continue
		}

		// The manifest is the UI source of truth, but disk wins when an upload
		// was saved and the final status write/response was interrupted.
		manifest.Files[index].Size = info.Size()
		manifest.Files[index].MimeType = mimeTypeForFile(path, file.Name)
		manifest.Files[index].Status = fileStatusReady
		changed = true
	}

	if changed {
		if err := writeBoxManifestUnlocked(boxID, manifest); err != nil {
			return manifest, err
		}
	}

	return manifest, nil
}

func createBoxManifest(boxID string, requests []models.CreateBoxFileRequest) ([]models.BoxFile, error) {
	usedNames := make(map[string]int, len(requests))
	files := make([]models.BoxFile, 0, len(requests))

	for _, request := range requests {
		filename, ok := safeFilename(request.Name)
		if !ok {
			return nil, fmt.Errorf("Invalid filename")
		}

		filename = uniqueManifestFilename(filename, usedNames)
		fileID, err := newFileID()
		if err != nil {
			return nil, fmt.Errorf("Could not create file id")
		}

		mimeType := mime.TypeByExtension(strings.ToLower(filepath.Ext(filename)))
		if mimeType == "" {
			mimeType = "application/octet-stream"
		}

		files = append(files, models.BoxFile{
			ID:       fileID,
			Name:     filename,
			Size:     request.Size,
			MimeType: mimeType,
			Status:   fileStatusWait,
		})
	}

	manifest := models.BoxManifest{Files: files}
	if err := writeBoxManifest(boxID, manifest); err != nil {
		return nil, err
	}

	decoratedFiles := make([]models.BoxFile, 0, len(files))
	for _, file := range files {
		decoratedFiles = append(decoratedFiles, decorateBoxFile(boxID, file))
	}

	return decoratedFiles, nil
}

func markManifestFileStatus(boxID string, fileID string, status string) (models.BoxFile, error) {
	if status != fileStatusWait && status != fileStatusWork && status != fileStatusReady && status != fileStatusFailed {
		return models.BoxFile{}, fmt.Errorf("Invalid file status")
	}

	boxManifestMu.Lock()
	defer boxManifestMu.Unlock()

	manifest, err := readBoxManifestUnlocked(boxID)
	if err != nil {
		return models.BoxFile{}, err
	}

	for index, file := range manifest.Files {
		if file.ID != fileID {
			continue
		}

		manifest.Files[index].Status = status
		if err := writeBoxManifestUnlocked(boxID, manifest); err != nil {
			return models.BoxFile{}, err
		}

		return decorateBoxFile(boxID, manifest.Files[index]), nil
	}

	return models.BoxFile{}, fmt.Errorf("File not found")
}

func readBoxManifest(boxID string) (models.BoxManifest, error) {
	boxManifestMu.Lock()
	defer boxManifestMu.Unlock()

	return readBoxManifestUnlocked(boxID)
}

func readBoxManifestUnlocked(boxID string) (models.BoxManifest, error) {
	var manifest models.BoxManifest
	data, err := os.ReadFile(manifestPath(boxID))
	if err != nil {
		return manifest, err
	}

	if err := json.Unmarshal(data, &manifest); err != nil {
		return manifest, err
	}

	return manifest, nil
}

func writeBoxManifest(boxID string, manifest models.BoxManifest) error {
	boxManifestMu.Lock()
	defer boxManifestMu.Unlock()

	return writeBoxManifestUnlocked(boxID, manifest)
}

// Manifest writes are serialized because the browser can upload several files
// concurrently into the same box. Without this lock, status updates can race.
func writeBoxManifestUnlocked(boxID string, manifest models.BoxManifest) error {
	data, err := json.MarshalIndent(manifest, "", "  ")
	if err != nil {
		return err
	}

	return os.WriteFile(manifestPath(boxID), data, 0644)
}