package lang

import (
	"strings"
	"testing"
)

// TestEmbeddedVersionMutation is the П0 acceptance test (D39.60 §6.1, "bytes ARE version" for the embed
// plane): a byte edit of an embedded data file MUST move EmbeddedVersion — so, once it is folded into the
// snapshot, an edit is a loud --resnapshot, never a silent verdict/wire change. It also pins the format and
// reproducibility (the same bytes always hash the same).
func TestEmbeddedVersionMutation(t *testing.T) {
	got := EmbeddedVersion()
	if !strings.HasPrefix(got, embedAlgoVersion+"-") {
		t.Fatalf("EmbeddedVersion() = %q, want %s-<hash>", got, embedAlgoVersion)
	}

	files := embeddedDataFiles()
	if len(files) == 0 {
		t.Fatal("no embedded data files")
	}
	if base := hashEmbeddedFiles(files); base != got {
		t.Fatalf("EmbeddedVersion not reproducible from embeddedDataFiles(): %s != %s", base, got)
	}

	// Mutate ONE byte of a verdict-bearing file (target-ru.txt drives the sanitizer) and a wire-bearing file
	// (injection.txt rides the request) — each must diverge the hash on its own.
	for _, target := range []string{"target-ru.txt", "injection.txt"} {
		mutated := make([]embeddedFile, len(files))
		copy(mutated, files)
		var found bool
		for i := range mutated {
			if mutated[i].name == target {
				b := append([]byte(nil), mutated[i].data...)
				b[len(b)/2] ^= 0x01 // flip a content byte
				mutated[i].data = b
				found = true
				break
			}
		}
		if !found {
			t.Fatalf("%s is not embedded", target)
		}
		if mut := hashEmbeddedFiles(mutated); mut == got {
			t.Errorf("a byte edit of %s did NOT move EmbeddedVersion (%s) — the embed plane would drift silently", target, mut)
		}
	}
}