package fiesta

import (
	"os"
	"os/exec"
	"strings"
	"testing"
)

// Fiesta is the design system on its own. Rastrillo adopts it, so a
// path from here back to Rastrillo would be a cycle, and a user who
// links the CSS from a static page has no Go at all. The two tests
// below are the two halves of that promise, executable: no build of
// this module reaches amadan.net/rastrillo/rastrillo, and the packages
// a Go program imports from Fiesta pull in no browser.

// rastrilloModule is the import path that must never appear in this
// module's dependency graph, and never in its go.mod.
const rastrilloModule = "amadan.net/rastrillo/rastrillo"

// listDeps runs go list with the given arguments and returns its
// output, one import path per line. A go list that cannot run fails
// the test rather than listing nothing: piped straight into a check,
// an empty listing would pass as clean, which is how a toolchain that
// could not fetch itself once passed rastrillo's own graph check.
func listDeps(t *testing.T, args ...string) []string {
	t.Helper()
	cmd := exec.Command("go", append([]string{"list"}, args...)...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		t.Fatalf("go list %s: %v\n%s", strings.Join(args, " "), err, out)
	}
	lines := strings.Split(strings.TrimRight(string(out), "\n"), "\n")
	if len(lines) == 0 || lines[0] == "" {
		t.Fatalf("go list %s printed nothing", strings.Join(args, " "))
	}
	return lines
}

// requireListed is the precondition that keeps either check honest: a
// listing that does not name this module's own package is not a
// listing of this module, whatever else it says.
func requireListed(t *testing.T, lines []string, args string) {
	t.Helper()
	for _, l := range lines {
		if l == "amadan.net/rastrillo/fiesta" {
			return
		}
	}
	t.Fatalf("go list %s did not list amadan.net/rastrillo/fiesta itself; the check below would be looking at nothing:\n%s", args, strings.Join(lines, "\n"))
}

// TestFiestaNeverImportsRastrillo is the global constraint "No
// Rastrillo dependency" as a test: every package of this module, its
// tests included and with the browser tag on (a strict superset of the
// plain build), imports nothing from amadan.net/rastrillo/rastrillo,
// and go.mod never requires it. The go.mod half catches a requirement
// nobody imports yet, which `go list -deps` alone would not see.
func TestFiestaNeverImportsRastrillo(t *testing.T) {
	mod, err := os.ReadFile("go.mod")
	if err != nil {
		t.Fatalf("reading go.mod: %v", err)
	}
	if strings.Contains(string(mod), rastrilloModule) {
		t.Errorf("go.mod mentions %s; Fiesta never requires Rastrillo", rastrilloModule)
	}

	args := "-deps -test -tags browser ./..."
	lines := listDeps(t, "-deps", "-test", "-tags", "browser", "./...")
	requireListed(t, lines, args)
	for _, l := range lines {
		if strings.HasPrefix(l, rastrilloModule) {
			t.Errorf("go list %s reaches %s; Fiesta never imports Rastrillo in any build, tag or test", args, l)
		}
	}
}

// TestThePublicPackagesLinkNoBrowser is the other half: the packages
// a Go program imports from Fiesta, the root and example, never link
// chromedp. The browser is for check/ and the drives, and an app that
// embeds the CSS must not take on a Chrome driver to do it.
func TestThePublicPackagesLinkNoBrowser(t *testing.T) {
	args := "-deps . ./example"
	lines := listDeps(t, "-deps", ".", "./example")
	requireListed(t, lines, args)
	for _, l := range lines {
		if strings.Contains(l, "chromedp") {
			t.Errorf("go list %s reaches %s; the public packages never link a browser", args, l)
		}
	}
}