package fiesta

import (
	"os"
	"strings"
	"testing"
	"time"
)

// This file is rastrillo's cssfloor_test.go aimed at Fiesta's two
// documents, plus the two checks that hold the README and the
// changelog to the release they describe.

// cssFloor is the engine floor the stylesheets impose on every page
// that links them. It is derived, not chosen: take the features
// tokens.css and the three themes use, and keep the highest engine
// version among them. light-dark() sets it everywhere except Firefox,
// where :has() does. Both documents state the result, because a
// reader who cannot find the floor invents one: an agent building on
// rastrillo once refused oklch() as "a 2023-era browser feature" and
// reached for hex twins, which protect nobody, since an engine too old
// for oklch() dropped the whole light-dark() palette several
// declarations earlier.
//
// Two files stating one fact can drift into two facts.
// TestCSSFloorIsStatedTheSameInBothFiles holds them equal. Both
// hard-wrap prose, so the comparison normalises whitespace: the string
// may break across a line, it may not disagree.
const cssFloor = "Chrome 123, Safari 17.5, Firefox 121"

// The adoption policy is a rolling one: a feature is fair game once it
// has been in all three engines about a year. A rolling policy with no
// clock is a lapsed one nobody has noticed yet, and these two constants
// are the clock.
//
// What does not move when the policy rolls is the floor. It rises only
// when someone writes a newer feature into the CSS, so "anything a year
// old may be used" and "today we bottom out at Chrome 123" stay true
// together. That is also why the review is by hand: the computable
// half, what is now a year old, was never the hard half. The judgement
// is which of those to want, and every yes raises the floor for every
// page that links the CSS.
//
// Nine months rather than twelve, so a review that slips a release
// still lands inside the year the policy names.
//
// Answering the failure means re-deriving, not bumping the date: list
// the features css/tokens.css and css/themes/*.css use, take the
// highest engine version among them, and if it differs from cssFloor
// change it here, in README.md and in DESIGN.md together. Then set
// floorReviewed to the day you did it.
const (
	floorReviewed     = "2026-09-01"
	floorReviewMonths = 9
)

// floorFiles are the documents that state the floor: the README, for
// someone deciding whether to link the CSS, and DESIGN.md, for someone
// writing against it.
var floorFiles = []string{"README.md", "DESIGN.md"}

// TestCSSFloorIsStatedTheSameInBothFiles fails when the README and
// DESIGN.md disagree about the floor, or either leaves it out. They
// are written for different readers, and a reader who checks one
// against the other and finds two numbers trusts neither.
func TestCSSFloorIsStatedTheSameInBothFiles(t *testing.T) {
	for _, path := range floorFiles {
		b, err := os.ReadFile(path)
		if err != nil {
			t.Errorf("%s must exist and state the floor %q: %v", path, cssFloor, err)
			continue
		}
		if !strings.Contains(strings.Join(strings.Fields(string(b)), " "), cssFloor) {
			t.Errorf("%s does not state the floor %q.\n"+
				"Either it drifted, or the floor moved and this file was not brought along: "+
				"cssFloor, README.md and DESIGN.md change together or not at all.",
				path, cssFloor)
		}
	}
}

// TestCSSFloorHasBeenReviewedRecently is the tripwire. It fails on a
// date, which is unusual and intended: the alternative is a warning,
// and a warning on a release evening is a thing you scroll past. A
// build that stops for ten minutes while somebody re-reads a list of
// CSS features is cheap; a floor that quietly describes 2024 while
// the policy promises "about a year" is the silence the policy exists
// to end.
func TestCSSFloorHasBeenReviewedRecently(t *testing.T) {
	reviewed, err := time.Parse(time.DateOnly, floorReviewed)
	if err != nil {
		t.Fatalf("floorReviewed must be a %s date: %v", time.DateOnly, err)
	}
	due := reviewed.AddDate(0, floorReviewMonths, 0)
	if time.Now().After(due) {
		t.Fatalf("the CSS floor was last reviewed %s and was due %s.\n"+
			"Re-derive it, the features css/tokens.css and css/themes/*.css use and the highest engine "+
			"version among them, then update cssFloor, README.md and DESIGN.md if it moved, and set "+
			"floorReviewed to today. Do not bump the date alone; the date is the record that somebody looked.",
			floorReviewed, due.Format(time.DateOnly))
	}
}

// changelogName is the file whose newest release must be Version.
const changelogName = "CHANGELOG.md"

// TestVersionIsTheChangelogsNewestRelease holds the changelog and the
// tree to one version: the first second-level heading is Unreleased,
// and the one after it names Version, so a release is cut only once
// its entry is written, and the tree is never a version the changelog
// has not heard of. TestTheVersionIsSemver pins Version itself.
func TestVersionIsTheChangelogsNewestRelease(t *testing.T) {
	b, err := os.ReadFile(changelogName)
	if err != nil {
		t.Fatalf("%s must exist, with ## Unreleased and then ## %s: %v", changelogName, Version, err)
	}
	var headings []string
	for _, line := range strings.Split(string(b), "\n") {
		if strings.HasPrefix(line, "## ") {
			headings = append(headings, strings.TrimSpace(line))
		}
	}
	if len(headings) < 2 {
		t.Fatalf("%s has %d second-level headings %q; want ## Unreleased and then ## %s", changelogName, len(headings), headings, Version)
	}
	if headings[0] != "## Unreleased" {
		t.Errorf("%s's first heading is %q, want %q", changelogName, headings[0], "## Unreleased")
	}
	if want := "## " + Version; headings[1] != want {
		t.Errorf("%s's newest release is %q, but the tree is %q: the changelog entry and fiesta.Version move together", changelogName, headings[1], want)
	}
}

// oneLink is the tag the README exists to show: a page links this and
// has the design system. /1/ is rewritten to the newest 1.y.z release.
const oneLink = `<link rel="stylesheet" href="https://fiesta.rastrillo.org/1/fiesta.css">`

// TestTheReadmeShowsTheOneLink: the README carries the link tag
// exactly as a page should paste it.
func TestTheReadmeShowsTheOneLink(t *testing.T) {
	b, err := os.ReadFile("README.md")
	if err != nil {
		t.Fatalf("README.md must exist and show the one link: %v", err)
	}
	if !strings.Contains(string(b), oneLink) {
		t.Errorf("README.md does not show the one link, verbatim: %s", oneLink)
	}
}