package service

import (
	"bytes"
	"encoding/base64"
	"image"
	"image/color"
	"image/png"
	"math/rand/v2"
	"strings"
	"time"
	"yintai-api/app/common/cache"
	err2 "yintai-api/app/common/err"

	"github.com/smbrave/goutil"
)

const captchaAlphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"

var captchaFont = map[rune][7]byte{
	'2': {0b01110, 0b10001, 0b00001, 0b00010, 0b00100, 0b01000, 0b11111},
	'3': {0b01110, 0b10001, 0b00001, 0b00110, 0b00001, 0b10001, 0b01110},
	'4': {0b00100, 0b01000, 0b10000, 0b10010, 0b11111, 0b00010, 0b00010},
	'5': {0b11111, 0b10000, 0b11110, 0b00001, 0b00001, 0b10001, 0b01110},
	'6': {0b00110, 0b01000, 0b10000, 0b11110, 0b10001, 0b10001, 0b01110},
	'7': {0b11111, 0b00001, 0b00010, 0b00100, 0b01000, 0b01000, 0b01000},
	'8': {0b01110, 0b10001, 0b10001, 0b01110, 0b10001, 0b10001, 0b01110},
	'9': {0b01110, 0b10001, 0b10001, 0b01111, 0b00001, 0b00010, 0b01100},
	'A': {0b01110, 0b10001, 0b10001, 0b11111, 0b10001, 0b10001, 0b10001},
	'B': {0b11110, 0b10001, 0b10001, 0b11110, 0b10001, 0b10001, 0b11110},
	'C': {0b01110, 0b10001, 0b10000, 0b10000, 0b10000, 0b10001, 0b01110},
	'D': {0b11110, 0b10001, 0b10001, 0b10001, 0b10001, 0b10001, 0b11110},
	'E': {0b11111, 0b10000, 0b10000, 0b11110, 0b10000, 0b10000, 0b11111},
	'F': {0b11111, 0b10000, 0b10000, 0b11110, 0b10000, 0b10000, 0b10000},
	'G': {0b01110, 0b10001, 0b10000, 0b10111, 0b10001, 0b10001, 0b01111},
	'H': {0b10001, 0b10001, 0b10001, 0b11111, 0b10001, 0b10001, 0b10001},
	'J': {0b00111, 0b00010, 0b00010, 0b00010, 0b00010, 0b10010, 0b01100},
	'K': {0b10001, 0b10010, 0b10100, 0b11000, 0b10100, 0b10010, 0b10001},
	'L': {0b10000, 0b10000, 0b10000, 0b10000, 0b10000, 0b10000, 0b11111},
	'M': {0b10001, 0b11011, 0b10101, 0b10101, 0b10001, 0b10001, 0b10001},
	'N': {0b10001, 0b11001, 0b10101, 0b10011, 0b10001, 0b10001, 0b10001},
	'P': {0b11110, 0b10001, 0b10001, 0b11110, 0b10000, 0b10000, 0b10000},
	'Q': {0b01110, 0b10001, 0b10001, 0b10001, 0b10101, 0b10010, 0b01101},
	'R': {0b11110, 0b10001, 0b10001, 0b11110, 0b10100, 0b10010, 0b10001},
	'S': {0b01111, 0b10000, 0b10000, 0b01110, 0b00001, 0b00001, 0b11110},
	'T': {0b11111, 0b00100, 0b00100, 0b00100, 0b00100, 0b00100, 0b00100},
	'U': {0b10001, 0b10001, 0b10001, 0b10001, 0b10001, 0b10001, 0b01110},
	'V': {0b10001, 0b10001, 0b10001, 0b10001, 0b10001, 0b01010, 0b00100},
	'W': {0b10001, 0b10001, 0b10001, 0b10101, 0b10101, 0b10101, 0b01010},
	'X': {0b10001, 0b10001, 0b01010, 0b00100, 0b01010, 0b10001, 0b10001},
	'Y': {0b10001, 0b10001, 0b01010, 0b00100, 0b00100, 0b00100, 0b00100},
	'Z': {0b11111, 0b00001, 0b00010, 0b00100, 0b01000, 0b10000, 0b11111},
}

func (a *User) Captcha() (string, string) {
	code := randomCaptcha(4)
	id := goutil.RandomStr(16)
	if err := cache.GetRedis().Set(cache.NewKeys().Captcha(id), code, 10*time.Minute).Err(); err != nil {
		err2.DbErr("<user captcha>", err)
	}
	return id, "data:image/png;base64," + base64.StdEncoding.EncodeToString(captchaPNG(code))
}

func verifyCaptcha(id, code string) {
	id = strings.TrimSpace(id)
	code = strings.TrimSpace(code)
	if id == "" {
		err2.CaptchaErr()
	}
	key := cache.NewKeys().Captcha(id)
	redix := cache.GetRedis()
	saved := redix.Get(key).Val()
	redix.Del(key)
	if code == "" || saved == "" || !strings.EqualFold(saved, code) {
		err2.CaptchaErr()
	}
}

func randomCaptcha(n int) string {
	buf := make([]byte, n)
	for i := range buf {
		buf[i] = captchaAlphabet[rand.IntN(len(captchaAlphabet))]
	}
	return string(buf)
}

func captchaPNG(code string) []byte {
	const scale = 3
	charW, charH := 5*scale, 7*scale
	gap, padX, padY := 10, 14, 12
	width := padX*2 + len(code)*charW + (len(code)-1)*gap
	height := padY*2 + charH + 8
	img := image.NewRGBA(image.Rect(0, 0, width, height))
	bg := color.RGBA{245, 246, 248, 255}
	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			img.Set(x, y, bg)
		}
	}
	for range 8 {
		c := color.RGBA{uint8(160 + rand.IntN(70)), uint8(160 + rand.IntN(70)), uint8(160 + rand.IntN(70)), 255}
		x1, y1 := rand.IntN(width), rand.IntN(height)
		x2, y2 := rand.IntN(width), rand.IntN(height)
		drawLine(img, x1, y1, x2, y2, c)
	}
	for i, r := range code {
		glyph, ok := captchaFont[r]
		if !ok {
			continue
		}
		ox := padX + i*(charW+gap) + rand.IntN(3) - 1
		oy := padY + rand.IntN(5)
		ink := color.RGBA{uint8(rand.IntN(80)), uint8(rand.IntN(80)), uint8(rand.IntN(80)), 255}
		for row := 0; row < 7; row++ {
			bits := glyph[row]
			for col := 0; col < 5; col++ {
				if bits&(1<<uint(4-col)) == 0 {
					continue
				}
				for dy := 0; dy < scale; dy++ {
					for dx := 0; dx < scale; dx++ {
						img.Set(ox+col*scale+dx, oy+row*scale+dy, ink)
					}
				}
			}
		}
	}
	var buf bytes.Buffer
	_ = png.Encode(&buf, img)
	return buf.Bytes()
}

func drawLine(img *image.RGBA, x1, y1, x2, y2 int, c color.Color) {
	dx := abs(x2 - x1)
	dy := abs(y2 - y1)
	sx, sy := 1, 1
	if x1 > x2 {
		sx = -1
	}
	if y1 > y2 {
		sy = -1
	}
	err := dx - dy
	for {
		if image.Pt(x1, y1).In(img.Bounds()) {
			img.Set(x1, y1, c)
		}
		if x1 == x2 && y1 == y2 {
			return
		}
		e2 := 2 * err
		if e2 > -dy {
			err -= dy
			x1 += sx
		}
		if e2 < dx {
			err += dx
			y1 += sy
		}
	}
}

func abs(n int) int {
	if n < 0 {
		return -n
	}
	return n
}