package lib

import (
	"bytes"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/devrites/devrites/internal/gate"
)

// driftWorkspace builds a workspace with every required readiness input.
func driftWorkspace(t *testing.T) (root, featureDir string) {
	t.Helper()
	root, featureDir = newWorkspace(t, "vet")
	for _, name := range []string{
		"spec.md", "decision-coverage.md", "architecture.md",
		"plan.md", "tasks.md", "traceability.md", "test-plan.md",
	} {
		writeFile(t, filepath.Join(featureDir, name), "# "+name+"\n\ncontent\n")
	}
	return root, featureDir
}

func checkDrift(t *testing.T, root string, args ...string) (int, string) {
	t.Helper()
	stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
	code := RunCheckDrift(root, args, stdout, stderr)
	return code, stdout.String() + stderr.String()
}

func TestDriftUnprovenWithoutBaselineOrBinding(t *testing.T) {
	root, _ := driftWorkspace(t)
	code, out := checkDrift(t, root, "feat")
	if code != 0 || !strings.Contains(out, "unproven") {
		t.Fatalf("code=%d out=%s", code, out)
	}
}

func TestDriftRecordThenCleanPass(t *testing.T) {
	root, _ := driftWorkspace(t)
	code, out := checkDrift(t, root, "feat", "--record")
	if code != 0 || !strings.Contains(out, "baseline recorded") {
		t.Fatalf("record code=%d out=%s", code, out)
	}
	code, out = checkDrift(t, root, "feat")
	if code != 0 || !strings.Contains(out, "drift: none") {
		t.Fatalf("compare code=%d out=%s", code, out)
	}
}

func TestDriftAttributesChangedFile(t *testing.T) {
	root, featureDir := driftWorkspace(t)
	if code, out := checkDrift(t, root, "feat", "--record"); code != 0 {
		t.Fatalf("record code=%d out=%s", code, out)
	}
	writeFile(t, filepath.Join(featureDir, "plan.md"), "# plan.md\n\nrewritten\n")
	writeFile(t, filepath.Join(featureDir, "strategy.md"), "# strategy\n\nnew optional input\n")
	code, out := checkDrift(t, root, "feat")
	if code != 0 {
		t.Fatalf("code=%d out=%s", code, out)
	}
	if !strings.Contains(out, "plan.md changed") || !strings.Contains(out, "strategy.md added") {
		t.Fatalf("expected per-file attribution:\n%s", out)
	}
	if strings.Contains(out, "spec.md changed") {
		t.Fatalf("spec.md did not change:\n%s", out)
	}
}

func TestDriftFallbackEngReviewBinding(t *testing.T) {
	root, featureDir := driftWorkspace(t)
	_, binding, err := gate.ReadinessInputDigests(root, "feat")
	if err != nil {
		t.Fatal(err)
	}
	writeFile(t, filepath.Join(featureDir, "eng-review.md"), "# Eng review\n\n"+binding+"\n")
	code, out := checkDrift(t, root, "feat")
	if code != 0 || !strings.Contains(out, "drift: none") {
		t.Fatalf("code=%d out=%s", code, out)
	}
	writeFile(t, filepath.Join(featureDir, "tasks.md"), "# tasks\n\ndrifted\n")
	// eng-review must predate the drifted file for the mtime heuristic.
	old := time.Now().Add(-time.Hour)
	if err := os.Chtimes(filepath.Join(featureDir, "eng-review.md"), old, old); err != nil {
		t.Fatal(err)
	}
	code, out = checkDrift(t, root, "feat")
	if code != 0 {
		t.Fatalf("code=%d out=%s", code, out)
	}
	if !strings.Contains(out, "DRIFT: readiness inputs changed") || !strings.Contains(out, "tasks.md") {
		t.Fatalf("expected aggregate drift + candidate:\n%s", out)
	}
}

func TestDriftCorruptBaselineBlocks(t *testing.T) {
	root, featureDir := driftWorkspace(t)
	writeFile(t, filepath.Join(featureDir, driftBaselineFile), "{not json")
	code, out := checkDrift(t, root, "feat")
	if code != 3 || !strings.Contains(out, "BLOCKED") {
		t.Fatalf("code=%d out=%s", code, out)
	}
}