package main

import (
	"fmt"
	"math"
	"time"
)

var (
	uiBg     = rgb{0x12, 0x14, 0x18}
	uiPanel  = rgb{0x1c, 0x20, 0x26}
	uiRule   = rgb{0x2e, 0x34, 0x3c}
	uiButton = rgb{0x25, 0x2b, 0x33}
	uiFg     = rgb{0xe6, 0xe8, 0xea}
	uiDim    = rgb{0x7a, 0x82, 0x8c}
	uiCyan   = rgb{0x5c, 0xc8, 0xe0}
	uiGreen  = rgb{0x4c, 0xc2, 0x6a}
	uiRed    = rgb{0xe0, 0x4b, 0x4b}
	uiYellow = rgb{0xe0, 0xb0, 0x40}
)

// Everything tabular sits on one monospace cell grid and every number is
// right-aligned to a column end, so columns line up by construction.
const (
	uiMargin = 16

	cellDirA  = 0
	cellArrow = 2
	cellDirB  = 4

	colTxGbEnd  = 14
	colTxPPSEnd = 27
	colRxGbEnd  = 37
	colRxPPSEnd = 50

	colFramesEnd = 18
	colDataEnd   = 27
	colLostEnd   = 38
	colLateEnd   = 46
	colCRCEnd    = 53
	colKdropEnd  = 62

	btnW         = 200
	btnH         = 64
	holdDuration = time.Second
)

type rect struct {
	x, y, w, h int
}

func (r rect) contains(x, y int) bool {
	return x >= r.x && x < r.x+r.w && y >= r.y && y < r.y+r.h
}

type display struct {
	fb    *framebuffer
	huge  *textFace
	grid  *textFace
	gridB *textFace
	small *textFace

	resetBtn  rect
	holdStart time.Time
	holdFrac  float64
	fired     bool
}

func newDisplay() (*display, error) {
	fb, err := openFramebuffer("/dev/fb0")
	if err != nil {
		return nil, err
	}
	d := &display{fb: fb}
	for _, spec := range []struct {
		dst  **textFace
		bold bool
		size float64
	}{
		{&d.huge, true, 72},
		{&d.grid, false, 24},
		{&d.gridB, true, 24},
		{&d.small, false, 18},
	} {
		face, err := loadFace(spec.bold, spec.size)
		if err != nil {
			fb.close()
			return nil, err
		}
		*spec.dst = face
	}
	if d.grid.cellW != d.gridB.cellW {
		fb.close()
		return nil, fmt.Errorf("grid faces disagree on cell width: %d vs %d",
			d.grid.cellW, d.gridB.cellW)
	}
	d.resetBtn = rect{
		x: fb.w - uiMargin - btnW,
		y: fb.h - uiMargin - btnH,
		w: btnW,
		h: btnH,
	}
	return d, nil
}

// Tracks a press and hold on the reset button, returning true once it has been
// held long enough. Lifting or sliding off cancels, and the press has to be
// released before it can arm again.
func (d *display) holdReset(x, y int, down bool, now time.Time) bool {
	if !down {
		d.holdStart, d.holdFrac, d.fired = time.Time{}, 0, false
		return false
	}
	if d.fired || !d.resetBtn.contains(x, y) {
		d.holdStart, d.holdFrac = time.Time{}, 0
		return false
	}
	if d.holdStart.IsZero() {
		d.holdStart = now
	}
	d.holdFrac = now.Sub(d.holdStart).Seconds() / holdDuration.Seconds()
	if d.holdFrac < 1 {
		return false
	}
	d.holdFrac, d.fired, d.holdStart = 0, true, time.Time{}
	return true
}

func (d *display) drawResetButton() {
	r := d.resetBtn
	d.fb.rect(r.x, r.y, r.w, r.h, uiButton)

	if d.holdFrac > 0 {
		w := int(float64(r.w) * math.Min(d.holdFrac, 1))
		d.fb.rect(r.x, r.y, w, r.h, uiCyan)
	}
	for _, e := range []rect{
		{r.x, r.y, r.w, 2},
		{r.x, r.y + r.h - 2, r.w, 2},
		{r.x, r.y, 2, r.h},
		{r.x + r.w - 2, r.y, 2, r.h},
	} {
		d.fb.rect(e.x, e.y, e.w, e.h, uiCyan)
	}

	label := "RESET"
	lx := r.x + (r.w-len(label)*d.gridB.cellW)/2
	ly := r.y + (r.h-d.gridB.cellH)/2
	// The label straddles the fill, so each glyph takes the colour that reads
	// against whatever is behind it.
	split := r.x + int(float64(r.w)*math.Min(d.holdFrac, 1))
	for i, c := range label {
		gx := lx + i*d.gridB.cellW
		col := uiFg
		if gx+d.gridB.cellW/2 < split {
			col = uiBg
		}
		d.gridB.draw(d.fb, gx, ly, string(c), col)
	}
}

func (d *display) close() {
	d.fb.close()
}

func (d *display) cellX(c int) int {
	return uiMargin + c*d.grid.cellW
}

func (d *display) at(c, y int, s string, col rgb) {
	d.grid.draw(d.fb, d.cellX(c), y, s, col)
}

func (d *display) atBold(c, y int, s string, col rgb) {
	d.gridB.draw(d.fb, d.cellX(c), y, s, col)
}

func (d *display) rightAt(cEnd, y int, s string, col rgb) {
	d.grid.draw(d.fb, d.cellX(cEnd)-len([]rune(s))*d.grid.cellW, y, s, col)
}

func (d *display) right(f *textFace, xEnd, y int, s string, col rgb) {
	f.draw(d.fb, xEnd-len([]rune(s))*f.cellW, y, s, col)
}

func (d *display) center(f *textFace, y int, s string, col rgb) {
	f.draw(d.fb, (d.fb.w-len([]rune(s))*f.cellW)/2, y, s, col)
}

// Rendered rates are quantised so the text only changes when the value moves
// meaningfully. Without this the low digits churn every frame no matter how
// long the averaging window is.
func roundPPS(v float64) uint64 {
	const unit = 1000
	if v < 0 {
		return 0
	}
	return uint64((v+unit/2)/unit) * unit
}

func errColor(n uint64) rgb {
	if n == 0 {
		return uiGreen
	}
	return uiRed
}

func rateColor(gb, target float64) rgb {
	switch {
	case gb >= target*rateGreenFrac:
		return uiGreen
	case gb >= target*rateYellowFrac:
		return uiYellow
	default:
		return uiRed
	}
}

func (d *display) render(dirs []*direction, views []view, elapsed time.Duration, target float64, cable string) {
	fb := d.fb
	fb.fill(uiBg)

	d.small.draw(fb, uiMargin, 10, "cabletest", uiCyan)
	d.small.draw(fb, uiMargin+11*d.small.cellW, 10,
		fmt.Sprintf("%s %s   %s %s", dirs[0].tx.tag, dirs[0].tx.name,
			dirs[0].rx.tag, dirs[0].rx.name), uiDim)
	d.right(d.small, fb.w-uiMargin, 10, uptime(elapsed), uiDim)

	var total uint64
	for _, v := range views {
		total += v.errors
	}

	bandY, bandH := 40, 150
	fb.rect(0, bandY, fb.w, bandH, uiPanel)
	fb.rect(0, bandY, 8, bandH, errColor(total))
	word, wc := "NO ERRORS", uiGreen
	if total > 0 {
		word, wc = fmt.Sprintf("%s ERRORS", commas(total)), uiRed
	}
	d.center(d.huge, bandY+(bandH-d.huge.cellH)/2, word, wc)

	// Two tight blocks rather than rows spread over the whole panel, centred in
	// what is left below the band.
	lineH := d.grid.cellH + 4
	sectionH := d.small.cellH + 10 + (1+len(dirs))*lineH
	gap := 30
	avail := fb.h - (bandY + bandH) - btnH - 2*uiMargin
	y := bandY + bandH + 8 + (avail-2*sectionH-gap)/2

	y = d.section(y, "RATE", "")
	d.rightAt(colTxGbEnd, y, "TX Gb/s", uiDim)
	d.rightAt(colTxPPSEnd, y, "TX pps", uiDim)
	d.rightAt(colRxGbEnd, y, "RX Gb/s", uiDim)
	d.rightAt(colRxPPSEnd, y, "RX pps", uiDim)
	y += lineH
	for i, dir := range dirs {
		d.dirTag(dir, y)
		v := views[i]
		d.rightAt(colTxGbEnd, y, fmt.Sprintf("%.2f", v.txGbps), rateColor(v.txGbps, target))
		d.rightAt(colTxPPSEnd, y, commas(roundPPS(v.txPPS)), uiFg)
		d.rightAt(colRxGbEnd, y, fmt.Sprintf("%.2f", v.rxGbps), rateColor(v.rxGbps, target))
		d.rightAt(colRxPPSEnd, y, commas(roundPPS(v.rxPPS)), uiFg)
		y += lineH
	}

	y += gap
	y = d.section(y, "OVERALL", cable)
	d.rightAt(colFramesEnd, y, "frames", uiDim)
	d.rightAt(colDataEnd, y, "data", uiDim)
	d.rightAt(colLostEnd, y, "lost", uiDim)
	d.rightAt(colLateEnd, y, "late", uiDim)
	d.rightAt(colCRCEnd, y, "crc", uiDim)
	d.rightAt(colKdropEnd, y, "kdrop", uiDim)
	y += lineH
	for i, dir := range dirs {
		d.dirTag(dir, y)
		v := views[i]
		d.rightAt(colFramesEnd, y, commas(v.txFrames), uiFg)
		d.rightAt(colDataEnd, y, humanBytes(v.txSent), uiFg)
		d.rightAt(colLostEnd, y, commas(v.lost), errColor(v.lost))
		d.rightAt(colLateEnd, y, commas(v.late), errColor(v.late))
		d.rightAt(colCRCEnd, y, commas(v.crc), errColor(v.crc))
		d.rightAt(colKdropEnd, y, commas(v.kdrop), errColor(v.kdrop))
		y += lineH
	}

	d.drawResetButton()
	fb.flush()
}

func (d *display) section(y int, title, right string) int {
	d.small.draw(d.fb, uiMargin, y, title, uiFg)
	if right != "" {
		d.right(d.small, d.cellX(colKdropEnd), y, right, uiCyan)
	}
	ruleY := y + d.small.cellH + 3
	d.fb.rect(uiMargin, ruleY, d.fb.w-2*uiMargin, 1, uiRule)
	return ruleY + 7
}

func (d *display) dirTag(dir *direction, y int) {
	d.atBold(cellDirA, y, dir.tx.tag, uiCyan)
	d.arrow(d.cellX(cellArrow), y+d.grid.cellH/2, uiDim)
	d.atBold(cellDirB, y, dir.rx.tag, uiCyan)
}

// Drawn because the font has no arrow glyph. Occupies exactly one cell so the
// grid is unaffected.
func (d *display) arrow(x, y int, c rgb) {
	w := d.grid.cellW
	d.fb.rect(x, y-1, w-5, 2, c)
	for i := 0; i < 6; i++ {
		d.fb.rect(x+w-6+i, y-5+i, 1, 11-2*i, c)
	}
}