//
// Copyright (c) 2019-2022 Markku Rossi
//
// All rights reserved.
//

package circuit

import (
	"fmt"
	"io"
	"sort"
)

const (
	ioWidth  = 32
	ioHeight = 32
	ioPadX   = 16
	ioPadY   = 32

	gateWidth  = 32
	gateHeight = 32
	gatePadX   = 16
	gatePadY   = 64
)

type tile struct {
	gate *Gate
	avg  float64
	x    float64
	y    float64
}

type point struct {
	x, y float64
}

type wireType int

const (
	wireTypeNormal wireType = iota
	wireTypeZero
	wireTypeOne
)

type wire struct {
	t    wireType
	from point
	to   point
}

func (w *wire) svg(out io.Writer) {
	label := "1"

	switch w.t {
	case wireTypeNormal:
		midY := w.from.y + (w.to.y-w.from.y)/2 - 5
		fmt.Fprintf(out, `    <path d="M %v %v
	         v %v
	         C %v %v %v %v %v %v
	         v %v" />
`,
			w.from.x, w.from.y,

			midY-w.from.y,

			w.from.x, midY+10,
			w.to.x, midY,
			w.to.x, midY+10,

			w.to.y-midY-10,
		)

	case wireTypeZero:
		label = "0"
		fallthrough

	case wireTypeOne:
		fmt.Fprintf(out, `    <g fill="#000">
      <text x="%v" y="%v" text-anchor="middle">%v</text>
    </g>
`,
			w.to.x, w.to.y-2, label)
	}
}

type svgCtx struct {
	wireStarts []point
	zero       Wire
	one        Wire
}

func (ctx *svgCtx) setWireType(input Wire, w *wire) {
	if input == ctx.zero {
		w.t = wireTypeZero
	} else if input == ctx.one {
		w.t = wireTypeOne
	}
}

func (ctx *svgCtx) tileAvgInputX(t *tile) {
	var count float64
	switch t.gate.Op {
	case XOR, XNOR, AND, OR:
		if t.gate.Input1 != ctx.zero && t.gate.Input1 != ctx.one {
			count++
			t.avg += ctx.wireStarts[t.gate.Input1].x
		}
		fallthrough

	case INV:
		if count == 0 ||
			(t.gate.Input0 != ctx.zero && t.gate.Input0 != ctx.one) {
			count++
			t.avg += ctx.wireStarts[t.gate.Input0].x
		}
	}
	t.avg /= count
	t.avg -= (gateWidth) / 2
}

// Svg creates an SVG output of the circuit.
func (c *Circuit) Svg(out io.Writer) {
	c.AssignLevels()

	cols := c.Stats[MaxWidth]
	rows := c.Stats[NumLevels]

	fmt.Printf("")

	// Header.

	ctx := &svgCtx{
		wireStarts: make([]point, c.NumWires),
		zero:       InvalidWire,
		one:        InvalidWire,
	}

	iw := uint64(ioPadX + c.Inputs.Size()*(ioWidth+ioPadX))
	ow := uint64(ioPadX + c.Outputs.Size()*(ioWidth+ioPadX))

	width := cols * (gateWidth + gatePadX)

	if iw > width {
		width = iw
	}
	if ow > width {
		width = ow
	}

	fmt.Fprintf(out,
		`<svg xmlns="http://www.w3.org/2000/svg" width="%d" height="%d">
  <style><![CDATA[
  text {
    font: 10px Courier, monospace;
  }
  ]]></style>
  <g fill="none" stroke="#000" stroke-width=".5">
`,
		width, rows*(gateHeight+gatePadY)+2*(ioHeight+gatePadY))

	// Input wires.
	leftPad := ioPadX + int((width-iw)/2)
	for i := 0; i < c.Inputs.Size(); i++ {
		p := point{
			x: float64(leftPad + i*(ioWidth+ioPadX)),
			y: ioHeight,
		}
		ctx.wireStarts[i] = p

		staticInput(out, p.x, p.y, fmt.Sprintf("i%v", i))
	}

	// Compute level widths.

	widths := make([]uint64, rows)

	var lastLevel Level
	var x, y int

	for _, g := range c.Gates {
		if g.Level != lastLevel {
			lastLevel = g.Level
			y++
		}
		widths[y]++
	}

	// Render circuit.

	var tiles []*tile
	var wires []*wire

	x = 0
	y = -1
	lastLevel = 0

	for idx, g := range c.Gates {
		if idx == 0 || g.Level != lastLevel {
			wires = append(wires, renderRow(out, int(width),
				float64(ioHeight+gatePadY+y*(gateHeight+gatePadY)), tiles,
				ctx)...)
			tiles = nil

			lastLevel = g.Level
			y++
			x = 0
		}
		tiles = append(tiles, &tile{
			gate: &c.Gates[idx],
		})
		x++
	}
	wires = append(wires, renderRow(out, int(width),
		float64(ioHeight+gatePadY+y*(gateHeight+gatePadY)), tiles, ctx)...)

	// Output wires.
	y++
	numOutputs := c.Outputs.Size()

	var oAvg float64
	for i := 0; i < numOutputs; i++ {
		oAvg += ctx.wireStarts[c.NumWires-numOutputs+i].x
	}
	oAvg /= float64(numOutputs)

	oWidth := float64((numOutputs-1)*(ioWidth+ioPadX) + ioWidth)

	leftPad = int(oAvg-oWidth/2) + ioWidth/2

	for i := 0; i < numOutputs; i++ {
		p := point{
			x: float64(leftPad + i*(ioWidth+ioPadX)),
			y: float64(ioHeight + gatePadY + y*(gateHeight+gatePadY)),
		}
		staticOutput(out, p.x, p.y, fmt.Sprintf("o%v", i))
		wires = append(wires, &wire{
			from: ctx.wireStarts[c.NumWires-numOutputs+i],
			to:   p,
		})
	}

	for _, w := range wires {
		w.svg(out)
	}

	fmt.Fprintln(out, "  </g>\n</svg>")
}

func renderRow(out io.Writer, width int, y float64, tiles []*tile,
	ctx *svgCtx) []*wire {

	var wires []*wire

	for _, t := range tiles {
		ctx.tileAvgInputX(t)
	}
	sort.Slice(tiles, func(i, j int) bool {
		return tiles[i].avg < tiles[j].avg
	})

	// Assign x based on input average and push tiles right.
	var next float64
	for _, t := range tiles {
		if next <= t.avg {
			t.x = t.avg
		} else {
			t.x = next
		}
		next = t.x + gateWidth + gatePadX
	}

	// Starting from the right end, shift tiles left until they are on
	// screen and not overlapping.
	next = float64(width) - gateWidth - gatePadX
	for i := len(tiles) - 1; i >= 0; i-- {
		if tiles[i].x > next {
			tiles[i].x = next
		}
		next -= gateWidth + gatePadX
	}

	for _, t := range tiles {
		wires = append(wires, t.gate.svg(out, t.x, y, ctx)...)
	}

	return wires
}

func (g *Gate) svg(out io.Writer, x, y float64, ctx *svgCtx) []*wire {
	fmt.Fprintf(out, `    <g transform="translate(%v %v)">
`,
		x, y)

	tmpl := templates[g.Op]
	if tmpl == nil {
		tmpl = templates[Count]
	}
	out.Write([]byte(tmpl.Expand()))
	fmt.Fprintln(out, `    </g>`)

	ctx.wireStarts[g.Output] = point{
		x: x + gateWidth/2,
		y: y + gateHeight,
	}

	var wires []*wire

	switch g.Op {
	case XOR, XNOR, AND, OR:
		x0 := x + intCvt(35)
		x1 := x + intCvt(65)

		f0 := ctx.wireStarts[g.Input0]
		f1 := ctx.wireStarts[g.Input1]

		w0 := &wire{
			from: f0,
			to: point{
				x: x0,
				y: y,
			},
		}
		w1 := &wire{
			from: f1,
			to: point{
				x: x1,
				y: y,
			},
		}
		ctx.setWireType(g.Input0, w0)
		ctx.setWireType(g.Input1, w1)

		// The input pin order does not matter in the
		// visualization. Swap input pins if input wires would cross
		// each other.
		if f0.x > f1.x {
			w0.to, w1.to = w1.to, w0.to
		}

		wires = append(wires, w0)
		wires = append(wires, w1)

	case INV:
		wire := &wire{
			from: ctx.wireStarts[g.Input0],
			to: point{
				x: x + intCvt(50),
				y: y,
			},
		}
		ctx.setWireType(g.Input0, wire)
		wires = append(wires, wire)
	}

	// Constant value gates.
	switch g.Op {
	case XOR:
		if g.Input0 == g.Input1 {
			ctx.zero = g.Output
			staticOutput(out, x+gateWidth/2, y+gateHeight, "0")
		}

	case XNOR:
		if g.Input0 == g.Input1 {
			fmt.Printf("*** one!\n")
			ctx.one = g.Output
			staticOutput(out, x+gateWidth/2, y+gateHeight, "1")
		}
	}

	return wires
}

func staticInput(out io.Writer, x, y float64, label string) {
	fmt.Fprintf(out, `    <g fill="#000">
      <text x="%v" y="%v" text-anchor="middle">%v</text>
    </g>
`,
		x, y-2, label)
}

func staticOutput(out io.Writer, x, y float64, label string) {
	fmt.Fprintf(out, `    <g fill="#000">
      <text x="%v" y="%v" text-anchor="middle">%v</text>
    </g>
`,
		x, y+10, label)
}

func scale(in int) float64 {
	return float64(in) * gateWidth / 100
}

func path(out io.Writer) {
	fmt.Fprintln(out, `  <path fill="none" stroke="#000" stroke-width=".5"`)
}

var templates [Count + 1]*Template

var intCvt IntCvt
var floatCvt FloatCvt

func init() {
	templates[XOR] = NewTemplate(`      <path d="M {{25}} {{20}}
               c {{10}} {{10}} {{40}} {{10}} {{50}} 0" />
      <path d="M {{25}} {{25}}
               c {{10}} {{10}} {{40}} {{10}} {{50}} 0" />
      <path d="M {{75}} {{25}}
               v {{25}}
               s 0 {{10}} {{-25}} {{25}}" />
      <path d="M {{25}} {{25}}
               v {{25}}
               s 0 {{10}} {{25}} {{25}}" />
      <path d="M {{35}} 0
               v {{25}}
               z" />
      <path d="M {{65}} 0
               v {{25}}
               z" />
      <path d="M {{50}} {{75}}
               v {{25}}
               z" />
`)
	templates[XNOR] = NewTemplate(`      <path d="M {{25}} {{20}}
               c {{10}} {{10}} {{40}} {{10}} {{50}} 0" />
      <path d="M {{25}} {{25}}
               c {{10}} {{10}} {{40}} {{10}} {{50}} 0" />
      <path d="M {{75}} {{25}}
               v {{25}}
               s 0 {{10}} {{-25}} {{25}}" />
      <path d="M {{25}} {{25}}
               v {{25}}
               s 0 {{10}} {{25}} {{25}}" />
      <circle cx="{{50}}" cy="{{80}}" r="{{5}}" />
      <path d="M {{35}} 0
               v {{25}}
               z" />
      <path d="M {{65}} 0
               v {{25}}
               z" />
      <path d="M {{50}} {{85}}
               v {{15}}
               z" />
`)

	templates[AND] = NewTemplate(`      <path d="M {{25}} {{25}}
               h {{50}}
               v {{25}}
               a {{25}} {{25}} 0 1 1 {{-50}} 0
               v {{-25}}
               z" />
      <path d="M {{35}} 0
               v {{25}}
               z" />
      <path d="M {{65}} 0
               v {{25}}
               z" />
      <path d="M {{50}} {{75}}
               v {{25}}
               z" />
`)

	templates[OR] = NewTemplate(`    <path d="M {{25}} {{20}}
               c {{10}} {{10}} {{40}} {{10}} {{50}} 0" />
      <path d="M {{75}} {{20}}
               v {{30}}
               s 0 {{10}} {{-25}} {{25}}" />
      <path d="M {{25}} {{20}}
               v {{30}}
               s 0 {{10}} {{25}} {{25}}" />
      <path d="M {{35}} 0
               v {{25}}
              z" />
      <path d="M {{65}} 0
               v {{25}}
               z" />
      <path d="M {{50}} {{75}}
               v {{25}}
               z" />
`)

	templates[INV] = NewTemplate(`      <path d="M {{25}} {{25}}
               h {{50}}
               l {{-25}} {{43}}
               z" />
      <circle cx="{{50}}" cy="{{73.5}}" r="{{5}}" />
      <path d="M {{50}} 0
               v {{25}}
               z" />
      <path d="M {{50}} {{79}}
               v {{21}}
               z" />
`)

	templates[Count] = NewTemplate(`<path
        d="M {{25}} {{25}} h {{50}} v{{50}} h {{-50}} z" />`)

	floatCvt = func(v float64) float64 {
		return v * gateWidth / 100
	}
	intCvt = func(v int) float64 {
		return float64(v) * gateWidth / 100
	}
	for op := XOR; op < Count+1; op++ {
		if templates[op] != nil {
			templates[op].FloatCvt = floatCvt
			templates[op].IntCvt = intCvt
		}
	}
}