package infinitime

import (
	"archive/zip"
	"encoding/json"
	"io"
	"os"
	"path/filepath"

	"go.arsenm.dev/infinitime/blefs"
)

// ResourceOperation represents an operation performed during
// resource loading
type ResourceOperation uint8

const (
	// ResourceOperationUpload represents the upload phase
	// of resource loading
	ResourceOperationUpload = iota
	// ResourceOperationRemoveObsolete represents the obsolete
	// file removal phase of resource loading
	ResourceOperationRemoveObsolete
)

// ResourceManifest is the structure of the resource manifest file
type ResourceManifest struct {
	Resources []Resource         `json:"resources"`
	Obsolete  []ObsoleteResource `json:"obsolete_files"`
}

// Resource represents a resource entry in the manifest
type Resource struct {
	Name string `json:"filename"`
	Path string `json:"path"`
}

// ObsoleteResource represents an obsolete file entry in the manifest
type ObsoleteResource struct {
	Path  string `json:"path"`
	Since string `json:"since"`
}

// ResourceLoadProgress contains information on the progress of
// a resource load
type ResourceLoadProgress struct {
	Operation ResourceOperation
	Name      string
	Total     int64
	Sent      int64
	Err       error
}

// LoadResources accepts a resources zip file and a BLE FS.
// It loads the resources from the zip onto the FS.
func LoadResources(file *os.File, fs *blefs.FS) (<-chan ResourceLoadProgress, error) {
	out := make(chan ResourceLoadProgress, 10)

	fi, err := file.Stat()
	if err != nil {
		return nil, err
	}

	r, err := zip.NewReader(file, fi.Size())
	if err != nil {
		return nil, err
	}

	m, err := r.Open("resources.json")
	if err != nil {
		return nil, err
	}

	var manifest ResourceManifest
	err = json.NewDecoder(m).Decode(&manifest)
	if err != nil {
		return nil, err
	}

	go func() {
		defer close(out)

		for _, file := range manifest.Obsolete {
			name := filepath.Base(file.Path)

			err := fs.RemoveAll(file.Path)
			if err != nil {
				out <- ResourceLoadProgress{
					Name:      name,
					Operation: ResourceOperationRemoveObsolete,
					Err:       err,
				}
				return
			}

			out <- ResourceLoadProgress{
				Name:      name,
				Operation: ResourceOperationRemoveObsolete,
			}
		}

		for _, file := range manifest.Resources {
			src, err := r.Open(file.Name)
			if err != nil {
				out <- ResourceLoadProgress{
					Name:      file.Name,
					Operation: ResourceOperationUpload,
					Err:       err,
				}
				return
			}

			srcFi, err := src.Stat()
			if err != nil {
				out <- ResourceLoadProgress{
					Name:      file.Name,
					Operation: ResourceOperationUpload,
					Total:     srcFi.Size(),
					Err:       err,
				}
				return
			}

			err = fs.MkdirAll(filepath.Dir(file.Path))
			if err != nil {
				out <- ResourceLoadProgress{
					Name:      file.Name,
					Operation: ResourceOperationUpload,
					Total:     srcFi.Size(),
					Err:       err,
				}
				return
			}

			dst, err := fs.Create(file.Path, uint32(srcFi.Size()))
			if err != nil {
				out <- ResourceLoadProgress{
					Name:      file.Name,
					Operation: ResourceOperationUpload,
					Total:     srcFi.Size(),
					Err:       err,
				}
				return
			}

			progCh := dst.Progress()
			go func() {
				for sent := range progCh {
					out <- ResourceLoadProgress{
						Name:      file.Name,
						Operation: ResourceOperationUpload,
						Total:     srcFi.Size(),
						Sent:      int64(sent),
					}

					if sent == uint32(srcFi.Size()) {
						return
					}
				}
			}()

			n, err := io.Copy(dst, src)
			if err != nil {
				out <- ResourceLoadProgress{
					Name:      file.Name,
					Operation: ResourceOperationUpload,
					Total:     srcFi.Size(),
					Sent:      n,
					Err:       err,
				}
				return
			}

			src.Close()
			dst.Close()
		}
	}()

	return out, nil
}