package web

import (
	"fmt"
	"html/template"
	"strings"
)

// Row is one labelled value in a ranked chart.
type Row struct {
	Label string
	Value float64
	// Note is shown beside the value: a second figure worth carrying, such as
	// how many requests made up a token total.
	Note string
}

// HBarChart ranks labelled values as horizontal bars.
//
// Horizontal because the labels are email addresses and model names. Rotated or
// truncated labels on a column chart are a way of saying the chart is more
// important than being able to read it, and here the label is the point: the
// question is which person or which model, not what shape the distribution is.
//
// One series, so no legend — the heading names it. The value is written at the
// end of each bar rather than on an axis, because a reader wants the number for
// the row they are looking at, not a scale to estimate it against.
func HBarChart(rows []Row, colour, unit string) template.HTML {
	return english.HBarChart(rows, colour, unit)
}

// HBarChart is the ranked chart with its figures, and what it says when it
// has none, in this language.
func (l *Lang) HBarChart(rows []Row, colour, unit string) template.HTML {
	if colour == "" {
		colour = "--viz-1"
	}
	if len(rows) == 0 {
		return `<p class="empty">` + escapeText(l.T("chart.nothing_yet")) + `</p>`
	}

	maxV := 0.0
	for _, r := range rows {
		if r.Value > maxV {
			maxV = r.Value
		}
	}
	if maxV <= 0 {
		maxV = 1
	}

	// HTML rather than an SVG of fixed width. The SVG gave the value 96 units
	// and "34.2k tok  114 req" did not fit, so the one figure a reader came for
	// was the one cut off. A grid lets the label and the value take the room
	// they need and gives the bar whatever is left.
	var b strings.Builder
	b.WriteString(`<div class="ranked" role="list">`)
	for _, r := range rows {
		pct := r.Value / maxV * 100
		if pct < 0.5 && r.Value > 0 {
			// A value that rounds to nothing still happened, and a bar of zero
			// width reads as no data rather than as a small number.
			pct = 0.5
		}
		value := l.Compact(r.Value) + unitSuffix(unit)
		title := r.Label + ": " + value
		if r.Note != "" {
			value += " · " + r.Note
		}
		fmt.Fprintf(&b, `<div class="rk" role="listitem" title="%s">`+
			`<span class="rk-label">%s</span>`+
			`<span class="rk-track"><i class="rk-bar" style="width:%.1f%%;background:var(%s)"></i></span>`+
			`<span class="rk-value">%s</span></div>`,
			escapeText(title), escapeText(r.Label), pct, cssVar(colour), escapeText(value))
	}
	b.WriteString(`</div>`)
	return template.HTML(b.String()) //nolint:gosec // every interpolation is escaped above
}

// Sparkline draws a value's recent shape beside its number.
//
// No axes, no labels, no gridlines. It answers "rising, falling or flat" and
// nothing else; a reader who wants a number reads the number it sits under.
func Sparkline(values []float64, colour string) template.HTML {
	return english.Sparkline(values, colour)
}

// Sparkline is the trend line, named for a screen reader in this language.
func (l *Lang) Sparkline(values []float64, colour string) template.HTML {
	if colour == "" {
		colour = "--viz-1"
	}
	if len(values) < 2 {
		return ""
	}
	const w, h = 120.0, 24.0

	maxV := 0.0
	for _, v := range values {
		if v > maxV {
			maxV = v
		}
	}
	if maxV <= 0 {
		// Flat at zero is a real answer — no traffic — and drawing it along the
		// bottom says so, where an empty box would read as a broken chart.
		maxV = 1
	}

	var b strings.Builder
	fmt.Fprintf(&b, `<svg viewBox="0 0 %.0f %.0f" width="%.0f" height="%.0f" `+
		`role="img" aria-label="%s">`, w, h, w, h, escapeText(l.T("chart.trend")))
	b.WriteString(`<polyline fill="none" stroke="var(` + cssVar(colour) + `)` +
		`" stroke-width="2" stroke-linejoin="round" stroke-linecap="round" points="`)
	step := w / float64(len(values)-1)
	for i, v := range values {
		fmt.Fprintf(&b, "%.1f,%.1f ", float64(i)*step, h-(v/maxV*(h-4))-2)
	}
	b.WriteString(`"/></svg>`)
	return template.HTML(b.String()) //nolint:gosec // numbers and a CSS var only
}

// trimLabel keeps a long label readable without letting it push the plot off
// the side. Long email addresses are the common case.
func trimLabel(s string, n int) string {
	if len(s) <= n {
		return s
	}
	if n <= 1 {
		return s[:n]
	}
	return s[:n-1] + "…"
}

func unitSuffix(unit string) string {
	if unit == "" {
		return ""
	}
	return " " + unit
}

func maxFloat(a, b float64) float64 {
	if a > b {
		return a
	}
	return b
}