package files

import (
	"compress/gzip"
	"context"
	"io"
	"os"
	"path/filepath"
	"strings"

	"go.alanpearce.eu/x/log"

	"github.com/a-h/templ"
	"github.com/andybalholm/brotli"
	"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 {
	return &Files{
		outputDirectory: outputDirectory,
		options:         opts,
		log:             logger,
	}
}

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

func (f *Files) OutputToFile(output io.Reader, filename string) error {
	if err := f.Mkdirp(filepath.Dir(filename)); err != nil {
		return err
	}
	f.log.Debug("outputting file", "filename", filename)
	file, err := f.OpenFileAndVariants(filename)
	if err != nil {
		return errors.WithMessage(err, "could not open output file")
	}
	defer file.Close()

	if _, err := io.Copy(file, output); err != nil {
		return errors.WithMessage(err, "could not write output file")
	}

	return nil
}

func (f *Files) RenderToFile(component templ.Component, filename string) error {
	if err := f.Mkdirp(filepath.Dir(filename)); err != nil {
		return err
	}
	f.log.Debug("outputting file", "filename", filename)
	file, err := f.OpenFileAndVariants(filename)
	if err != nil {
		return errors.WithMessage(err, "could not open output file")
	}
	defer file.Close()

	if err := component.Render(context.TODO(), file); err != nil {
		return errors.WithMessage(err, "could not write output file")
	}

	return nil
}

func (f *Files) WriterToFile(writer io.WriterTo, filename string) error {
	if err := f.Mkdirp(filepath.Dir(filename)); err != nil {
		return err
	}
	f.log.Debug("outputting file", "filename", filename)
	file, err := f.OpenFileAndVariants(filename)
	if err != nil {
		return errors.WithMessage(err, "could not open output file")
	}
	defer file.Close()

	if _, err := writer.WriteTo(file); err != nil {
		return errors.WithMessage(err, "could not write output file")
	}

	return nil
}

type MultiWriteCloser struct {
	writers     []io.WriteCloser
	multiWriter io.Writer
}

func (mw *MultiWriteCloser) Write(p []byte) (n int, err error) {
	return mw.multiWriter.Write(p)
}

func (mw *MultiWriteCloser) Close() error {
	var lastErr error
	for _, w := range mw.writers {
		err := w.Close()
		if err != nil {
			lastErr = err
		}
	}

	return lastErr
}

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 multiOpenFile(filename string) (*MultiWriteCloser, 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
	}

	return &MultiWriteCloser{
		writers:     []io.WriteCloser{r, gz, br},
		multiWriter: io.MultiWriter(r, gz, br),
	}, 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 {
	f.log.Debug("creating directory", "dir", dir)
	err := os.MkdirAll(filepath.Join(f.outputDirectory, dir), 0755)

	return errors.WithMessage(err, "could not create directory")
}

func (f *Files) join(filename string) string {
	if strings.HasSuffix(filename, "/") {
		filename = filename + "index.html"
	}
	return filepath.Join(f.outputDirectory, filename)
}