// 一次性 icon 生成工具 — 產 visionA Local logo 的多種解析度 PNG
// 用法：go run gen_icon.go <output-dir>
//
// 此檔案為 standalone 工具，不屬於 visiona-local app。
// 用 build tag 避免被一般 go build 抓到（只有明確 go run 才執行）。
//go:build ignore

package main

import (
	"fmt"
	"image"
	"image/color"
	"image/png"
	"math"
	"os"
	"path/filepath"
	"strconv"
)

var (
	bgTop      = color.RGBA{0x1A, 0x1F, 0x36, 0xFF}
	bgBottom   = color.RGBA{0x0E, 0x12, 0x22, 0xFF}
	lensTop    = color.RGBA{0x6E, 0xA8, 0xFF, 0xFF}
	lensBot    = color.RGBA{0x4F, 0x7E, 0xFF, 0xFF}
	lensMid    = color.RGBA{0x4F, 0x7E, 0xFF, 0x99}
	centerGlow = color.RGBA{0x6E, 0xF3, 0xC5, 0xE0}
	white      = color.RGBA{0xFF, 0xFF, 0xFF, 0xFF}
	mint       = color.RGBA{0x6E, 0xF3, 0xC5, 0xFF}
	lightBlue  = color.RGBA{0x6E, 0xA8, 0xFF, 0xFF}
)

func lerpColor(a, b color.RGBA, t float64) color.RGBA {
	if t < 0 {
		t = 0
	}
	if t > 1 {
		t = 1
	}
	return color.RGBA{
		R: uint8(float64(a.R)*(1-t) + float64(b.R)*t),
		G: uint8(float64(a.G)*(1-t) + float64(b.G)*t),
		B: uint8(float64(a.B)*(1-t) + float64(b.B)*t),
		A: uint8(float64(a.A)*(1-t) + float64(b.A)*t),
	}
}

func blendAlpha(dst, src color.RGBA) color.RGBA {
	if src.A == 0 {
		return dst
	}
	if src.A == 0xFF {
		return src
	}
	sa := float64(src.A) / 255.0
	da := float64(dst.A) / 255.0
	out := 1.0 - (1.0-sa)*(1.0-da)
	if out == 0 {
		return dst
	}
	return color.RGBA{
		R: uint8((float64(src.R)*sa + float64(dst.R)*da*(1-sa)) / out),
		G: uint8((float64(src.G)*sa + float64(dst.G)*da*(1-sa)) / out),
		B: uint8((float64(src.B)*sa + float64(dst.B)*da*(1-sa)) / out),
		A: uint8(out * 255),
	}
}

func rgba(c color.Color) color.RGBA {
	if r, ok := c.(color.RGBA); ok {
		return r
	}
	r, g, b, a := c.RGBA()
	return color.RGBA{R: uint8(r >> 8), G: uint8(g >> 8), B: uint8(b >> 8), A: uint8(a >> 8)}
}

func drawRoundedRect(img *image.RGBA, size int, radius float64, colorAt func(y int) color.RGBA) {
	cx, cy := float64(size)/2, float64(size)/2
	for y := 0; y < size; y++ {
		c := colorAt(y)
		for x := 0; x < size; x++ {
			dx := math.Max(0, math.Abs(float64(x)-cx+0.5)-(float64(size)/2-radius))
			dy := math.Max(0, math.Abs(float64(y)-cy+0.5)-(float64(size)/2-radius))
			d := math.Hypot(dx, dy)
			if d <= radius {
				a := 1.0
				if d > radius-1 {
					a = radius - d
				}
				if a < 0 {
					continue
				}
				if a > 1 {
					a = 1
				}
				cc := c
				cc.A = uint8(float64(cc.A) * a)
				img.Set(x, y, blendAlpha(rgba(img.At(x, y)), cc))
			}
		}
	}
}

func drawCircleRing(img *image.RGBA, cx, cy, rOuter, rInner float64, c color.RGBA) {
	size := img.Bounds().Dx()
	for y := int(cy-rOuter-1) - 1; y <= int(cy+rOuter+1)+1; y++ {
		for x := int(cx-rOuter-1) - 1; x <= int(cx+rOuter+1)+1; x++ {
			if x < 0 || y < 0 || x >= size || y >= size {
				continue
			}
			d := math.Hypot(float64(x)-cx+0.5, float64(y)-cy+0.5)
			if d <= rOuter && d >= rInner {
				a := 1.0
				if d > rOuter-1 {
					a = rOuter - d
				} else if d < rInner+1 {
					a = d - rInner
				}
				if a < 0 {
					continue
				}
				if a > 1 {
					a = 1
				}
				cc := c
				cc.A = uint8(float64(cc.A) * a)
				img.Set(x, y, blendAlpha(rgba(img.At(x, y)), cc))
			}
		}
	}
}

func drawFilledCircle(img *image.RGBA, cx, cy, r float64, c color.RGBA) {
	size := img.Bounds().Dx()
	for y := int(cy-r-1) - 1; y <= int(cy+r+1)+1; y++ {
		for x := int(cx-r-1) - 1; x <= int(cx+r+1)+1; x++ {
			if x < 0 || y < 0 || x >= size || y >= size {
				continue
			}
			d := math.Hypot(float64(x)-cx+0.5, float64(y)-cy+0.5)
			if d <= r {
				a := 1.0
				if d > r-1 {
					a = r - d
				}
				if a < 0 {
					continue
				}
				cc := c
				cc.A = uint8(float64(cc.A) * a)
				img.Set(x, y, blendAlpha(rgba(img.At(x, y)), cc))
			}
		}
	}
}

func drawRadialGlow(img *image.RGBA, cx, cy, r float64, c color.RGBA) {
	size := img.Bounds().Dx()
	for y := int(cy-r-1) - 1; y <= int(cy+r+1)+1; y++ {
		for x := int(cx-r-1) - 1; x <= int(cx+r+1)+1; x++ {
			if x < 0 || y < 0 || x >= size || y >= size {
				continue
			}
			d := math.Hypot(float64(x)-cx+0.5, float64(y)-cy+0.5)
			if d <= r {
				t := 1.0 - d/r
				t = t * t
				cc := c
				cc.A = uint8(float64(cc.A) * t)
				img.Set(x, y, blendAlpha(rgba(img.At(x, y)), cc))
			}
		}
	}
}

func drawLine(img *image.RGBA, x1, y1, x2, y2, width float64, c color.RGBA) {
	size := img.Bounds().Dx()
	r := width / 2
	minX := int(math.Min(x1, x2) - r - 1)
	maxX := int(math.Max(x1, x2) + r + 1)
	minY := int(math.Min(y1, y2) - r - 1)
	maxY := int(math.Max(y1, y2) + r + 1)
	dx := x2 - x1
	dy := y2 - y1
	lenSq := dx*dx + dy*dy
	for y := minY; y <= maxY; y++ {
		for x := minX; x <= maxX; x++ {
			if x < 0 || y < 0 || x >= size || y >= size {
				continue
			}
			px := float64(x) + 0.5
			py := float64(y) + 0.5
			var t float64
			if lenSq > 0 {
				t = ((px-x1)*dx + (py-y1)*dy) / lenSq
				if t < 0 {
					t = 0
				}
				if t > 1 {
					t = 1
				}
			}
			cx := x1 + t*dx
			cy := y1 + t*dy
			d := math.Hypot(px-cx, py-cy)
			if d <= r {
				a := 1.0
				if d > r-1 {
					a = r - d
				}
				if a < 0 {
					continue
				}
				cc := c
				cc.A = uint8(float64(cc.A) * a)
				img.Set(x, y, blendAlpha(rgba(img.At(x, y)), cc))
			}
		}
	}
}

func renderLogo(size int) *image.RGBA {
	img := image.NewRGBA(image.Rect(0, 0, size, size))
	s := float64(size)
	k := s / 1024.0

	radius := 220.0 * k
	drawRoundedRect(img, size, radius, func(y int) color.RGBA {
		t := float64(y) / s
		return lerpColor(bgTop, bgBottom, t)
	})

	cx := 512.0 * k
	cy := 512.0 * k
	outerR := 360.0 * k
	outerW := 36.0 * k
	drawCircleRing(img, cx, cy, outerR, outerR-outerW, lensTop)
	drawCircleRing(img, cx, cy, outerR, outerR-outerW/2, lerpColor(lensTop, lensBot, 0.6))

	midR := 296.0 * k
	midW := 14.0 * k
	drawCircleRing(img, cx, cy, midR, midR-midW, lensMid)

	glowR := 240.0 * k
	drawRadialGlow(img, cx, cy, glowR, centerGlow)

	lineW := 44.0 * k
	drawLine(img, 360*k, 360*k, 512*k, 640*k, lineW, white)
	drawLine(img, 664*k, 360*k, 512*k, 640*k, lineW, white)

	drawFilledCircle(img, 360*k, 360*k, 22*k, mint)
	drawFilledCircle(img, 664*k, 360*k, 22*k, lightBlue)
	drawFilledCircle(img, 512*k, 640*k, 26*k, white)

	drawFilledCircle(img, 760*k, 264*k, 14*k, mint)
	drawCircleRing(img, 760*k, 264*k, 24*k, 21*k, color.RGBA{0x6E, 0xF3, 0xC5, 0x66})

	return img
}

func savePNG(img *image.RGBA, path string) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	f, err := os.Create(path)
	if err != nil {
		return err
	}
	defer f.Close()
	return png.Encode(f, img)
}

func main() {
	if len(os.Args) < 2 {
		fmt.Fprintln(os.Stderr, "usage: go run gen_icon.go <output-dir>")
		os.Exit(1)
	}
	outDir := os.Args[1]
	sizes := []int{16, 24, 32, 48, 64, 96, 128, 256, 512, 1024}
	for _, s := range sizes {
		img := renderLogo(s)
		path := filepath.Join(outDir, "icon-"+strconv.Itoa(s)+".png")
		if err := savePNG(img, path); err != nil {
			fmt.Fprintln(os.Stderr, "save", path, err)
			os.Exit(1)
		}
		fmt.Println("wrote", path)
	}
}