//go:build !android

// Package camera.
package camera

import (
	"fmt"
	"image"
	"io"
	"slices"

	"github.com/korandiz/v4l"

	im "github.com/gen2brain/cam2ip/image"
)

// supportedFormats lists the formats the camera can decode, in order of preference.
var supportedFormats = []uint32{
	mjpgFourCC, jpegFourCC,
	yuyvFourCC, uyvyFourCC, yvyuFourCC, vyuyFourCC,
	nv12FourCC, yu12FourCC, yv12FourCC,
	rgb24FourCC, bgr24FourCC,
	greyFourCC,
}

// Camera represents camera.
type Camera struct {
	opts   Options
	camera *v4l.Device
	config v4l.DeviceConfig
	ycbcr  *image.YCbCr
	rgba   *image.RGBA
	gray   *image.Gray
}

// New returns new Camera for given camera index.
func New(opts Options) (c *Camera, err error) {
	c = &Camera{}
	c.opts = opts

	devices := v4l.FindDevices()
	if len(devices) < opts.Index+1 {
		err = fmt.Errorf("camera: no camera at index %d", opts.Index)

		return
	}

	c.camera, err = v4l.Open(devices[opts.Index].Path)
	if err != nil {
		err = fmt.Errorf("camera: %w", err)

		return
	}

	if c.camera == nil {
		err = fmt.Errorf("camera: can not open camera %d", opts.Index)

		return
	}

	defer func() {
		if err != nil {
			c.camera.Close()
			c.camera = nil
		}
	}()

	configs, e := c.camera.ListConfigs()
	if e != nil {
		err = fmt.Errorf("camera: can not list configs: %w", e)

		return
	}

	formats := make([]uint32, 0)
	for _, config := range configs {
		formats = append(formats, config.Format)
	}

	c.config, err = c.camera.GetConfig()
	if err != nil {
		err = fmt.Errorf("camera: can not get config: %w", err)

		return
	}

	format, ok := selectFormat(formats)
	if !ok {
		err = fmt.Errorf("camera: no supported pixel format")

		return
	}
	c.config.Format = format

	c.config.Width = int(opts.Width)
	c.config.Height = int(opts.Height)

	err = c.camera.SetConfig(c.config)
	if err != nil {
		err = fmt.Errorf("camera: format %d: can not set config: %w", c.config.Format, err)

		return
	}

	rect := image.Rect(0, 0, int(c.opts.Width), int(c.opts.Height))

	switch c.config.Format {
	case yuy2FourCC, yuyvFourCC, uyvyFourCC, yvyuFourCC, vyuyFourCC:
		c.ycbcr = image.NewYCbCr(rect, image.YCbCrSubsampleRatio422)
	case nv12FourCC, yu12FourCC, yv12FourCC:
		c.ycbcr = image.NewYCbCr(rect, image.YCbCrSubsampleRatio420)
	case rgb24FourCC, bgr24FourCC:
		c.rgba = image.NewRGBA(rect)
	case greyFourCC:
		c.gray = image.NewGray(rect)
	}

	err = c.camera.TurnOn()
	if err != nil {
		err = fmt.Errorf("camera: format %d: can not turn on: %w", c.config.Format, err)

		return
	}

	return
}

// selectFormat returns the first supported format the device offers.
func selectFormat(formats []uint32) (uint32, bool) {
	for _, f := range supportedFormats {
		if slices.Contains(formats, f) {
			return f, true
		}
	}

	return 0, false
}

// Read reads next frame from camera and returns image.
func (c *Camera) Read() (img image.Image, err error) {
	buffer, err := c.camera.Capture()
	if err != nil {
		err = fmt.Errorf("camera: format %d: can not grab frame: %w", c.config.Format, err)

		return
	}

	if c.config.Format == mjpgFourCC || c.config.Format == jpegFourCC {
		img, err = im.NewDecoder(buffer).Decode()
		if err != nil {
			err = fmt.Errorf("camera: format %d: can not decode frame: %w", c.config.Format, err)

			return
		}
	} else {
		data, e := io.ReadAll(buffer)
		if e != nil {
			err = fmt.Errorf("camera: format %d: can not read buffer: %w", c.config.Format, e)

			return
		}

		img, err = c.convert(data)
		if err != nil {
			err = fmt.Errorf("camera: format %d: can not retrieve frame: %w", c.config.Format, err)

			return
		}
	}

	if c.opts.Rotate != 0 {
		img = im.Rotate(img, c.opts.Rotate)
	}

	if c.opts.Flip != "" {
		img = im.Flip(img, c.opts.Flip)
	}

	if c.opts.Timestamp {
		img = im.Timestamp(img, c.opts.TimeFormat)
	}

	return
}

// convert converts a raw frame in the negotiated format to an image.
func (c *Camera) convert(data []byte) (image.Image, error) {
	if y0, y1, cb, cr, ok := packed422Offsets(c.config.Format); ok {
		return c.ycbcr, packedYUV422ToYCbCr(data, c.ycbcr, y0, y1, cb, cr)
	}

	switch c.config.Format {
	case yu12FourCC:
		return c.ycbcr, planar420ToYCbCr(data, c.ycbcr, false)
	case yv12FourCC:
		return c.ycbcr, planar420ToYCbCr(data, c.ycbcr, true)
	case nv12FourCC:
		return c.ycbcr, nv12ToYCbCr(data, c.ycbcr)
	case rgb24FourCC:
		return c.rgba, rgb24ToRgba(data, c.rgba, false)
	case bgr24FourCC:
		return c.rgba, rgb24ToRgba(data, c.rgba, true)
	case greyFourCC:
		return c.gray, greyToGray(data, c.gray)
	}

	return nil, fmt.Errorf("unsupported format %d", c.config.Format)
}

// Close closes camera.
func (c *Camera) Close() (err error) {
	if c.camera == nil {
		err = fmt.Errorf("camera: close: camera is not opened")

		return
	}

	c.camera.TurnOff()
	c.camera.Close()
	c.camera = nil

	return
}

// Info returns the negotiated capture format.
func (c *Camera) Info() Info {
	return Info{Format: fourccName(c.config.Format), Width: c.config.Width, Height: c.config.Height}
}

// Devices returns the available capture devices.
func Devices() ([]DeviceInfo, error) {
	infos := v4l.FindDevices()
	devices := make([]DeviceInfo, 0, len(infos))

	for i, d := range infos {
		name := d.DeviceName
		if name == "" {
			name = d.Path
		}

		devices = append(devices, DeviceInfo{Index: i, Name: name})
	}

	return devices, nil
}