package gallery

import (
	"strings"

	"golang.org/x/text/language"
	"golang.org/x/text/message"
	"golang.org/x/text/number"

	"amadan.net/rastrillo/fiesta/internal/build"
)

// What a file weighs. The Getting started page gives each shipped file
// two figures, the bytes as written and gzipped, computed at render
// time from the release build's bytes. Neither is typed into prose or
// pinned in a test: compressor output can move between Go versions, so
// a golden figure would churn on a toolchain bump while proving
// nothing. Rastrillo's third figure, gzipped without comments, has no
// place here: a release file is already stripped, so the line's third
// part is always dropped.

// weightSep is the separator the weight line's parts are cut at. The
// stripped figure is the last part after it in every language, so a
// file with no stripped figure loses that part rather than repeating
// the gzipped figure under a different name.
const weightSep = " · "

// weight is one file's figures, in bytes.
type weight struct {
	Raw, Gzip int
}

// weigh measures one file: its length, and its length gzipped at level
// 6, the level a server or edge that compresses on the fly typically
// uses, through the release build's own compressor so the two agree.
func weigh(body []byte) weight {
	return weight{Raw: len(body), Gzip: build.Gzipped(body)}
}

// kib formats a byte count in KiB (1024; lowercase "kb" is kilobits)
// in the page's own number format: one decimal below 10 KiB, where
// rounding to a whole number would turn a 634-byte theme into "1" or
// "0", and whole numbers above, where a decimal is noise. The digits
// and separators are the locale's own, as x/text writes them.
func kib(locale string, n int) string {
	tag, err := language.Parse(locale)
	if err != nil {
		tag = language.English
	}
	p := message.NewPrinter(tag)
	v := float64(n) / 1024
	if n < 10*1024 {
		return p.Sprint(number.Decimal(v, number.MinFractionDigits(1), number.MaxFractionDigits(1)))
	}
	return p.Sprint(number.Decimal(v, number.MaxFractionDigits(0)))
}

// weightIn is one file's line in one locale: the weight line with its
// last part, the stripped figure, cut off, since no release file has
// one, and the two figures written in.
func (s *site) weightIn(locale string, w weight) string {
	line := s.say(locale, "gallery.started.weight")
	if i := strings.LastIndex(line, weightSep); i >= 0 {
		line = line[:i]
	}
	return interpolate(line, []string{"raw", kib(locale, w.Raw), "gzip", kib(locale, w.Gzip)})
}