package files

import (
	"compress/gzip"
	"io"
	"os"
	"path/filepath"
	"time"

	"go.alanpearce.eu/website/internal/buffer"
	"go.alanpearce.eu/website/internal/multibuf"
	"go.alanpearce.eu/website/internal/storage"
	"go.alanpearce.eu/x/log"

	"github.com/andybalholm/brotli"
	"github.com/klauspost/compress/zstd"
	"gitlab.com/tozd/go/errors"
)

const (
	gzipLevel   = 6
	brotliLevel = 9
)

type Files struct {
	outputDirectory string
	options         *Options
	log             *log.Logger
}

type Options struct {
	Compress bool
}

func NewWriter(outputDirectory string, logger *log.Logger, opts *Options) (*Files, error) {
	return &Files{
		outputDirectory: outputDirectory,
		options:         opts,
		log:             logger,
	}, nil
}

func (f *Files) NewFile(path string) *storage.File {
	return &storage.File{
		Path:         path,
		ContentType:  "",
		LastModified: time.Time{},
		Etag:         "",
		Encodings: map[string]io.ReadSeeker{
			"identity": nil,
		},
	}
}

func (f *Files) OpenRead(filename string) (io.ReadCloser, error) {
	return os.Open(f.join(filename))
}

func (f *Files) OpenWrite(filename string) (io.WriteCloser, error) {
	return openFileWrite(f.join(filename))
}

func (f *Files) Write(pathname string, content *buffer.Buffer) error {
	filename := pathNameToFileName(pathname)
	err := f.Mkdirp(filepath.Dir(filename))
	if err != nil {
		return errors.WithMessage(err, "could not create directory")
	}

	fd, err := f.OpenFileAndVariants(filename)
	if err != nil {
		return errors.WithMessagef(err, "could not open output file")
	}
	defer fd.Close()

	_, err = fd.Write(content.Bytes())
	if err != nil {
		return errors.WithMessage(err, "could not write output file")
	}

	return nil
}

func openFileWrite(filename string) (*os.File, error) {
	return os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
}

func openFileGz(filename string) (*gzip.Writer, error) {
	filenameGz := filename + ".gz"
	f, err := openFileWrite(filenameGz)
	if err != nil {
		return nil, err
	}

	return gzip.NewWriterLevel(f, gzipLevel)
}

func openFileBrotli(filename string) (*brotli.Writer, error) {
	filenameBrotli := filename + ".br"
	f, err := openFileWrite(filenameBrotli)
	if err != nil {
		return nil, err
	}

	return brotli.NewWriterLevel(f, brotliLevel), nil
}

func openFileZstd(filename string) (*zstd.Encoder, error) {
	f, err := openFileWrite(filename + ".zstd")
	if err != nil {
		return nil, err
	}

	return zstd.NewWriter(f)
}

func multiOpenFile(filename string) (*multibuf.WriteCloser, error) {
	r, err := openFileWrite(filename)
	if err != nil {
		return nil, err
	}
	gz, err := openFileGz(filename)
	if err != nil {
		return nil, err
	}
	br, err := openFileBrotli(filename)
	if err != nil {
		return nil, err
	}
	zst, err := openFileZstd(filename)
	if err != nil {
		return nil, err
	}

	return multibuf.NewWriteCloser(r, gz, br, zst), nil
}

func (f *Files) OpenFileAndVariants(filename string) (io.WriteCloser, error) {
	if f.options.Compress {
		return multiOpenFile(f.join(filename))
	}

	return openFileWrite(f.join(filename))
}

func (f *Files) Mkdirp(dir string) error {
	err := os.MkdirAll(f.join(dir), 0755)
	if err != nil {
		return errors.WithMessage(err, "could not create directory")
	}

	return nil
}

func (f *Files) join(filename string) string {
	return filepath.Join(f.outputDirectory, pathNameToFileName(filename))
}