package mem

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"
	"time"

	"github.com/markbates/pkger/here"
	"github.com/markbates/pkger/pkging"
)

const timeFmt = time.RFC3339Nano

var _ pkging.File = &File{}

type File struct {
	info   *pkging.FileInfo
	her    here.Info
	path   here.Path
	data   []byte
	parent here.Path
	writer *bytes.Buffer
	reader io.Reader
	pkging pkging.Pkger
}

type fJay struct {
	Info   *pkging.FileInfo `json:"info"`
	Her    here.Info        `json:"her"`
	Path   here.Path        `json:"path"`
	Data   []byte           `json:"data"`
	Parent here.Path        `json:"parent"`
}

func (f File) MarshalJSON() ([]byte, error) {
	return json.Marshal(fJay{
		Info:   f.info,
		Her:    f.her,
		Path:   f.path,
		Data:   f.data,
		Parent: f.parent,
	})
}

func (f *File) UnmarshalJSON(b []byte) error {
	var y fJay
	if err := json.Unmarshal(b, &y); err != nil {
		return err
	}
	f.info = y.Info
	f.her = y.Her
	f.path = y.Path
	f.data = y.Data
	f.parent = y.Parent
	return nil
}

// Seek sets the offset for the next Read or Write on file to offset, interpreted according to whence: 0 means relative to the origin of the file, 1 means relative to the current offset, and 2 means relative to the end. It returns the new offset and an error, if any.
func (f *File) Seek(ofpkginget int64, whence int) (int64, error) {
	if sk, ok := f.reader.(io.Seeker); ok {
		return sk.Seek(ofpkginget, whence)
	}
	return 0, nil
}

// Close closes the File, rendering it unusable for I/O.
func (f *File) Close() error {
	defer func() {
		f.reader = nil
		f.writer = nil
	}()
	if f.reader != nil {
		if c, ok := f.reader.(io.Closer); ok {
			if err := c.Close(); err != nil {
				return err
			}
		}
	}

	if f.writer == nil {
		return nil
	}

	f.data = f.writer.Bytes()

	fi := f.info
	fi.Details.Size = int64(len(f.data))
	fi.Details.ModTime = pkging.ModTime(time.Now())
	f.info = fi
	return nil
}

// Read reads up to len(b) bytes from the File. It returns the number of bytes read and any error encountered. At end of file, Read returns 0, io.EOF.
func (f *File) Read(p []byte) (int, error) {
	if len(f.data) > 0 && f.reader == nil {
		f.reader = bytes.NewReader(f.data)
	}

	if f.reader != nil {
		return f.reader.Read(p)
	}

	return 0, fmt.Errorf("unable to read %s", f.Name())
}

// Write writes len(b) bytes to the File. It returns the number of bytes written and an error, if any. Write returns a non-nil error when n != len(b).
func (f *File) Write(b []byte) (int, error) {
	if f.writer == nil {
		f.writer = &bytes.Buffer{}
	}
	i, err := f.writer.Write(b)
	return i, err
}

// Info returns the here.Info of the file
func (f File) Info() here.Info {
	return f.her
}

// Stat returns the FileInfo structure describing file. If there is an error, it will be of type *PathError.
func (f File) Stat() (os.FileInfo, error) {
	if f.info == nil {
		return nil, os.ErrNotExist
	}
	return f.info, nil
}

// Name retuns the name of the file
func (f File) Name() string {
	return f.info.Name()
}

// Abs returns an absolute representation of the file. If the path is not absolute it will be joined with the current working directory to turn it into an absolute path. The absolute path name for a given file is not guaranteed to be unique. Abs calls Clean on the result.
func (f File) Abs() (string, error) {
	return f.pkging.AbsPath(f.Path())
}

// Path returns the here.Path of the file
func (f File) Path() here.Path {
	return f.path
}

func (f File) String() string {
	return f.Path().String()
}

// Readdir reads the contents of the directory associated with file and returns a slice of up to n FileInfo values, as would be returned by Lstat, in directory order. Subsequent calls on the same file will yield further FileInfos.
//
// If n > 0, Readdir returns at most n FileInfo structures. In this case, if Readdir returns an empty slice, it will return a non-nil error explaining why. At the end of a directory, the error is io.EOF.
//
// If n <= 0, Readdir returns all the FileInfo from the directory in a single slice. In this case, if Readdir succeeds (reads all the way to the end of the directory), it returns the slice and a nil error. If it encounters an error before the end of the directory, Readdir returns the FileInfo read until that point and a non-nil error.
func (f *File) Readdir(count int) ([]os.FileInfo, error) {
	var infos []os.FileInfo
	root := f.Path().String()
	err := f.pkging.Walk(root, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if count > 0 && len(infos) == count {
			return io.EOF
		}

		if root == path {
			return nil
		}

		pt, err := f.pkging.Parse(path)
		if err != nil {
			return err
		}
		if pt.Name == f.parent.Name {
			return nil
		}

		info = pkging.WithRelName(strings.TrimPrefix(info.Name(), f.parent.Name), info)
		infos = append(infos, info)
		if info.IsDir() && path != root {
			return filepath.SkipDir
		}

		return nil
	})

	if err != nil {
		if _, ok := err.(*os.PathError); ok {
			return infos, nil
		}
		if err != io.EOF {
			return nil, err
		}
	}
	return infos, nil

}

// Open implements the http.FileSystem interface. A FileSystem implements access to a collection of named files. The elements in a file path are separated by slash ('/', U+002F) characters, regardless of host operating system convention.
func (f *File) Open(name string) (http.File, error) {
	pt, err := f.her.Parse(name)
	if err != nil {
		return nil, err
	}

	if pt == f.path {
		return f, nil
	}

	pt.Name = path.Join(f.Path().Name, pt.Name)

	di, err := f.pkging.Open(pt.String())
	if err != nil {
		return nil, err
	}

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

	if fi.IsDir() {
		d2 := &File{
			info:   pkging.NewFileInfo(fi),
			her:    di.Info(),
			path:   pt,
			parent: f.path,
			pkging: f.pkging,
		}
		di = d2
	}
	return di, nil
}