// Package st7789 implements a driver for the ST7789 TFT displays, it comes in various screen sizes.
//
// Datasheet: https://cdn-shop.adafruit.com/product-files/3787/3787_tft_QT154H2201__________20190228182902.pdf
//
package st7789 // import "tinygo.org/x/drivers/st7789"

import (
	"image/color"
	"machine"
	"time"

	"errors"
)

type Rotation uint8

// Device wraps an SPI connection.
type Device struct {
	bus             machine.SPI
	dcPin           machine.Pin
	resetPin        machine.Pin
	blPin           machine.Pin
	width           int16
	height          int16
	columnOffsetCfg int16
	rowOffsetCfg    int16
	columnOffset    int16
	rowOffset       int16
	rotation        Rotation
	batchLength     int32
	isBGR           bool
}

// Config is the configuration for the display
type Config struct {
	Width        int16
	Height       int16
	Rotation     Rotation
	RowOffset    int16
	ColumnOffset int16
}

// New creates a new ST7789 connection. The SPI wire must already be configured.
func New(bus machine.SPI, resetPin, dcPin, blPin machine.Pin) Device {
	dcPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
	resetPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
	blPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
	return Device{
		bus:      bus,
		dcPin:    dcPin,
		resetPin: resetPin,
		blPin:    blPin,
	}
}

// Configure initializes the display with default configuration
func (d *Device) Configure(cfg Config) {
	if cfg.Width != 0 {
		d.width = cfg.Width
	} else {
		d.width = 240
	}
	if cfg.Height != 0 {
		d.height = cfg.Height
	} else {
		d.height = 240
	}
	d.rotation = cfg.Rotation

	if cfg.RowOffset != 0 {
		d.rowOffsetCfg = cfg.RowOffset
	} else {
		d.rowOffsetCfg = 80
	}
	if cfg.ColumnOffset != 0 {
		d.columnOffsetCfg = cfg.ColumnOffset
	}

	d.batchLength = int32(d.width)
	if d.height > d.width {
		d.batchLength = int32(d.height)
	}
	d.batchLength += d.batchLength & 1

	// reset the device
	d.resetPin.High()
	time.Sleep(5 * time.Millisecond)
	d.resetPin.Low()
	time.Sleep(20 * time.Millisecond)
	d.resetPin.High()
	time.Sleep(150 * time.Millisecond)

	// Common initialization
	d.Command(SWRESET)
	time.Sleep(150 * time.Millisecond)
	d.Command(SLPOUT)
	time.Sleep(500 * time.Millisecond)
	d.Command(COLMOD)
	d.Data(0x55)
	time.Sleep(10 * time.Millisecond)

	d.SetRotation(d.rotation)
	d.InvertColors(true)

	d.Command(NORON)
	time.Sleep(10 * time.Millisecond)
	d.Command(DISPON)
	time.Sleep(500 * time.Millisecond)

	d.blPin.High()
}

// Display does nothing, there's no buffer as it might be too big for some boards
func (d *Device) Display() error {
	return nil
}

// SetPixel sets a pixel in the screen
func (d *Device) SetPixel(x int16, y int16, c color.RGBA) {
	if x < 0 || y < 0 ||
		(((d.rotation == NO_ROTATION || d.rotation == ROTATION_180) && (x >= d.width || y >= d.height)) ||
			((d.rotation == ROTATION_90 || d.rotation == ROTATION_270) && (x >= d.height || y >= d.width))) {
		return
	}
	d.FillRectangle(x, y, 1, 1, c)
}

// setWindow prepares the screen to be modified at a given rectangle
func (d *Device) setWindow(x, y, w, h int16) {
	x += d.columnOffset
	y += d.rowOffset
	d.Tx([]uint8{CASET}, true)
	d.Tx([]uint8{uint8(x << 8), uint8(x), uint8((x + w - 1) >> 8), uint8(x + w - 1)}, false)
	d.Tx([]uint8{RASET}, true)
	d.Tx([]uint8{uint8(y >> 8), uint8(y), uint8((y + h - 1) >> 8), uint8(y + h - 1)}, false)
	d.Command(RAMWR)
}

// FillRectangle fills a rectangle at a given coordinates with a color
func (d *Device) FillRectangle(x, y, width, height int16, c color.RGBA) error {
	k, i := d.Size()
	if x < 0 || y < 0 || width <= 0 || height <= 0 ||
		x >= k || (x+width) > k || y >= i || (y+height) > i {
		return errors.New("rectangle coordinates outside display area")
	}
	d.setWindow(x, y, width, height)
	c565 := RGBATo565(c)
	c1 := uint8(c565 >> 8)
	c2 := uint8(c565)

	data := make([]uint8, d.batchLength*2)
	for i := int32(0); i < d.batchLength; i++ {
		data[i*2] = c1
		data[i*2+1] = c2
	}
	j := int32(width) * int32(height)
	for j > 0 {
		if j >= d.batchLength {
			d.Tx(data, false)
		} else {
			d.Tx(data[:j*2], false)
		}
		j -= d.batchLength
	}
	return nil
}

// FillRectangle fills a rectangle at a given coordinates with a buffer
func (d *Device) FillRectangleWithBuffer(x, y, width, height int16, buffer []color.RGBA) error {
	i, j := d.Size()
	if x < 0 || y < 0 || width <= 0 || height <= 0 ||
		x >= i || (x+width) > i || y >= j || (y+height) > j {
		return errors.New("rectangle coordinates outside display area")
	}
	if int32(width)*int32(height) != int32(len(buffer)) {
		return errors.New("buffer length does not match with rectangle size")
	}
	d.setWindow(x, y, width, height)

	k := int32(width) * int32(height)
	data := make([]uint8, d.batchLength*2)
	offset := int32(0)
	for k > 0 {
		for i := int32(0); i < d.batchLength; i++ {
			if offset+i < int32(len(buffer)) {
				c565 := RGBATo565(buffer[offset+i])
				c1 := uint8(c565 >> 8)
				c2 := uint8(c565)
				data[i*2] = c1
				data[i*2+1] = c2
			}
		}
		if k >= d.batchLength {
			d.Tx(data, false)
		} else {
			d.Tx(data[:k*2], false)
		}
		k -= d.batchLength
		offset += d.batchLength
	}
	return nil
}

// DrawFastVLine draws a vertical line faster than using SetPixel
func (d *Device) DrawFastVLine(x, y0, y1 int16, c color.RGBA) {
	if y0 > y1 {
		y0, y1 = y1, y0
	}
	d.FillRectangle(x, y0, 1, y1-y0+1, c)
}

// DrawFastHLine draws a horizontal line faster than using SetPixel
func (d *Device) DrawFastHLine(x0, x1, y int16, c color.RGBA) {
	if x0 > x1 {
		x0, x1 = x1, x0
	}
	d.FillRectangle(x0, y, x1-x0+1, y, c)
}

// FillScreen fills the screen with a given color
func (d *Device) FillScreen(c color.RGBA) {
	if d.rotation == NO_ROTATION || d.rotation == ROTATION_180 {
		d.FillRectangle(0, 0, d.width, d.height, c)
	} else {
		d.FillRectangle(0, 0, d.height, d.width, c)
	}
}

// SetRotation changes the rotation of the device (clock-wise)
func (d *Device) SetRotation(rotation Rotation) {
	madctl := uint8(0)
	switch rotation % 4 {
	case 0:
		madctl = MADCTL_MX | MADCTL_MY
		d.rowOffset = d.rowOffsetCfg
		d.columnOffset = d.columnOffsetCfg
		break
	case 1:
		madctl = MADCTL_MY | MADCTL_MV
		d.rowOffset = d.columnOffsetCfg
		d.columnOffset = d.rowOffsetCfg
		break
	case 2:
		d.rowOffset = 0
		d.columnOffset = 0
		break
	case 3:
		madctl = MADCTL_MX | MADCTL_MV
		d.rowOffset = 0
		d.columnOffset = 0
		break
	}
	if d.isBGR {
		madctl |= MADCTL_BGR
	}
	d.Command(MADCTL)
	d.Data(madctl)

}

// Command sends a command to the display
func (d *Device) Command(command uint8) {
	d.Tx([]byte{command}, true)
}

// Command sends a data to the display
func (d *Device) Data(data uint8) {
	d.Tx([]byte{data}, false)
}

// Tx sends data to the display
func (d *Device) Tx(data []byte, isCommand bool) {
	if isCommand {
		d.dcPin.Low()
		d.bus.Tx(data, nil)
	} else {
		d.dcPin.High()
		d.bus.Tx(data, nil)
	}
}

// Size returns the current size of the display.
func (d *Device) Size() (w, h int16) {
	if d.rotation == NO_ROTATION || d.rotation == ROTATION_180 {
		return d.width, d.height
	}
	return d.height, d.width
}

// EnableBacklight enables or disables the backlight
func (d *Device) EnableBacklight(enable bool) {
	if enable {
		d.blPin.High()
	} else {
		d.blPin.Low()
	}
}

// InverColors inverts the colors of the screen
func (d *Device) InvertColors(invert bool) {
	if invert {
		d.Command(INVON)
	} else {
		d.Command(INVOFF)
	}
}

// IsBGR changes the color mode (RGB/BGR)
func (d *Device) IsBGR(bgr bool) {
	d.isBGR = bgr
}

// RGBATo565 converts a color.RGBA to uint16 used in the display
func RGBATo565(c color.RGBA) uint16 {
	r, g, b, _ := c.RGBA()
	return uint16((r & 0xF800) +
		((g & 0xFC00) >> 5) +
		((b & 0xF800) >> 11))
}