package main

import (
	"crypto/sha256"
	"fmt"
	"net/http"
	"strings"
)

// An avatar is drawn from the name alone: fetching one tells somewhere else
// who reads what, and an upload needs a parser.
func avatarSVG(name string) []byte {
	sum := sha256.Sum256([]byte(name))
	// Fixed saturation and lightness, so every one is readable.
	hue := int(sum[0]) * 360 / 256
	var b strings.Builder
	fmt.Fprintf(&b, `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 5 5" width="20" height="20" role="img" aria-label="%s">`, name)
	fmt.Fprintf(&b, `<rect width="5" height="5" fill="#eee"/>`)
	fmt.Fprintf(&b, `<g fill="hsl(%d,45%%,35%%)">`, hue)
	// Three columns mirrored into five.
	for x := range 3 {
		for y := range 5 {
			if sum[1+x*5+y]&1 == 0 {
				continue
			}
			fmt.Fprintf(&b, `<rect x="%d" y="%d" width="1" height="1"/>`, x, y)
			if x < 2 {
				fmt.Fprintf(&b, `<rect x="%d" y="%d" width="1" height="1"/>`, 4-x, y)
			}
		}
	}
	b.WriteString(`</g></svg>`)
	return []byte(b.String())
}

func (f *Forge) handleAvatar(w http.ResponseWriter, r *http.Request) {
	name := r.PathValue("name")
	if !accountNameRE.MatchString(name) {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "image/svg+xml")
	w.Header().Set("Cache-Control", "max-age=86400")
	w.Write(avatarSVG(name))
}