/*
Copyright © 2024 filifa

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package cmd

import (
	"encoding/binary"
	"errors"
	"io"
	"log"
	"os"

	"github.com/spf13/cobra"
	"github.com/veandco/go-sdl2/sdl"
)

var presets []string
var transition bool

/*
 * checkStdin checks if any data has been passed in through stdin and returns
 * an error if we don't believe so.
 */
func checkStdin() error {
	stat, err := os.Stdin.Stat()
	if err != nil {
		return err
	} else if (stat.Mode() & os.ModeCharDevice) != 0 {
		return errors.New("nothing to read from stdin")
	}

	return nil
}

/*
 * validatePresets performs some basic checks on the presets passed in and
 * returns an error if it finds a problem.
 */
func validatePresets() error {
	for _, p := range presets {
		info, err := os.Stat(p)
		if err != nil {
			return err
		} else if info.IsDir() {
			return errors.New("preset " + p + " is a directory")
		}
	}

	return nil
}

/*
 * handleWindowEvent handles window events like resizing.
 */
func handleWindowEvent(event *sdl.WindowEvent, m *milkDropWindow) {
	switch event.Event {
	case sdl.WINDOWEVENT_RESIZED:
		w, h := event.Data1, event.Data2
		m.resize(w, h)
	}
}

/*
 * handleKeyboardEvent handles keyboard inputs.
 */
func handleKeyboardEvent(event *sdl.KeyboardEvent, m *milkDropWindow) {
	scancode := event.Keysym.Scancode
	if event.Type == sdl.KEYDOWN && scancode == sdl.SCANCODE_RIGHT && event.Repeat == 0 {
		m.nextPreset(transition)
	} else if event.Type == sdl.KEYDOWN && scancode == sdl.SCANCODE_LEFT && event.Repeat == 0 {
		m.prevPreset(transition)
	}
}

/*
 * handleEvent passes the event to a more specific function based on its type.
 * It returns false if the program should quit, true otherwise.
 */
func handleEvent(event sdl.Event, m *milkDropWindow) bool {
	switch event.(type) {
	case *sdl.QuitEvent:
		return false
	case *sdl.WindowEvent:
		event := event.(*sdl.WindowEvent)
		handleWindowEvent(event, m)
	case *sdl.KeyboardEvent:
		event := event.(*sdl.KeyboardEvent)
		handleKeyboardEvent(event, m)
	}

	return true
}

/*
 * update handles events and renders new frames of the visualization. It
 * returns a bool indicating whether the program should keep running and an
 * error, if any.
 */
func update(m *milkDropWindow) (bool, error) {
	for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
		keepRunning := handleEvent(event, m)
		if !keepRunning {
			return false, nil
		}
	}

	audioData := make([]int16, 2048)

	err := binary.Read(os.Stdin, binary.LittleEndian, audioData)
	if err == io.ErrUnexpectedEOF {
		return false, nil
	} else if err != nil {
		return true, err
	}

	m.render(audioData)
	return true, nil
}

/*
 * milkbucket sets up the program and starts a rendering loop.
 */
func milkbucket(cmd *cobra.Command, args []string) {
	err := checkStdin()
	if err != nil {
		log.Fatal(err)
	}

	err = sdl.Init(sdl.INIT_VIDEO)
	if err != nil {
		log.Fatal(err)
	}
	defer sdl.Quit()

	err = validatePresets()
	if err != nil {
		log.Fatal(err)
	}

	m, err := newMilkDropWindow(800, 600, presets)
	if err != nil {
		log.Fatal(err)
	}
	defer m.destroy()

	m.loadPreset(false)

	running := true
	for running {
		running, err = update(m)
		if err != nil {
			log.Fatal(err)
		}
	}
}

// rootCmd represents the base command when called without any subcommands
var rootCmd = &cobra.Command{
	Use:   "milkbucket",
	Short: "Audio visualizer",
	Long: `milkbucket is an audio visualizer.

It uses Milkdrop preset files to generate visualizations from standard input.`,
	Run: milkbucket,
}

// Execute adds all child commands to the root command and sets flags appropriately.
// This is called by main.main(). It only needs to happen once to the rootCmd.
func Execute() {
	err := rootCmd.Execute()
	if err != nil {
		os.Exit(1)
	}
}

func init() {
	// Here you will define your flags and configuration settings.
	// Cobra supports persistent flags, which, if defined here,
	// will be global for your application.

	// Cobra also supports local flags, which will only run
	// when this action is called directly.
	rootCmd.Flags().BoolVarP(&transition, "transition", "t", false, "smoothly transition between presets")

	rootCmd.Flags().StringArrayVarP(&presets, "presets", "p", []string{}, "preset files to use")
}