package versioningapi

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"testing"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"

	dmscrypto "gitea.perlbach24.de/scripte/nexarch/dms/internal/crypto"
	"gitea.perlbach24.de/scripte/nexarch/dms/internal/storage"
	"gitea.perlbach24.de/scripte/nexarch/dms/internal/versioning"
)

type fakeKEKProvider struct{ kek []byte }

func (f *fakeKEKProvider) TenantKEK(ctx context.Context, tenantSlug string) ([]byte, error) {
	return f.kek, nil
}
type noopUsageReporter struct{}

func (noopUsageReporter) Report(ctx context.Context, tenantSlug, metric string, delta int64) error {
	return nil
}

type testEnv struct {
	pool    *pgxpool.Pool
	storage *storage.Service
	crypto  *dmscrypto.Service
	server  *httptest.Server
}

func setupTest(t *testing.T) (*testEnv, string, string) {
	t.Helper()
	dsn := os.Getenv("TEST_TENANT_DSN")
	if dsn == "" {
		t.Skip("TEST_TENANT_DSN nicht gesetzt, Integrationstest uebersprungen")
	}
	ctx := context.Background()
	pool, err := pgxpool.New(ctx, dsn)
	if err != nil {
		t.Fatalf("pool: %v", err)
	}
	t.Cleanup(func() { pool.Close() })

	if _, err := pool.Exec(ctx, `
		CREATE EXTENSION IF NOT EXISTS pgcrypto;
		CREATE TABLE IF NOT EXISTS users (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(), email TEXT NOT NULL UNIQUE, name TEXT NOT NULL,
			status TEXT NOT NULL DEFAULT 'active', created_at TIMESTAMPTZ NOT NULL DEFAULT now(), updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
		);
		CREATE TABLE IF NOT EXISTS documents (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(), folder_id UUID,
			title TEXT NOT NULL, current_revision_id UUID, created_by UUID NOT NULL REFERENCES users(id),
			created_at TIMESTAMPTZ NOT NULL DEFAULT now(), updated_at TIMESTAMPTZ NOT NULL DEFAULT now(), deleted_at TIMESTAMPTZ
		);
		CREATE TABLE IF NOT EXISTS file_revisions (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(), document_id UUID NOT NULL REFERENCES documents(id) ON DELETE CASCADE,
			revision_number INT NOT NULL, storage_key TEXT NOT NULL, checksum_sha256 TEXT NOT NULL,
			size_bytes BIGINT NOT NULL, mime_type TEXT NOT NULL, created_by UUID NOT NULL REFERENCES users(id),
			created_at TIMESTAMPTZ NOT NULL DEFAULT now(), wrapped_dek BYTEA, comment TEXT,
			UNIQUE (document_id, revision_number)
		);
		CREATE TABLE IF NOT EXISTS document_locks (
			document_id UUID PRIMARY KEY REFERENCES documents(id) ON DELETE CASCADE,
			locked_by UUID NOT NULL REFERENCES users(id), locked_at TIMESTAMPTZ NOT NULL DEFAULT now(),
			lease_until TIMESTAMPTZ NOT NULL
		);
	`); err != nil {
		t.Fatalf("schema: %v", err)
	}
	t.Cleanup(func() {
		_, _ = pool.Exec(context.Background(), `TRUNCATE document_locks, file_revisions, documents, users CASCADE`)
	})

	var userA, userB string
	if err := pool.QueryRow(ctx, `INSERT INTO users (email, name) VALUES ($1, 'A') RETURNING id`, fmt.Sprintf("verapi-a-%d@example.test", time.Now().UnixNano())).Scan(&userA); err != nil {
		t.Fatalf("user a: %v", err)
	}
	if err := pool.QueryRow(ctx, `INSERT INTO users (email, name) VALUES ($1, 'B') RETURNING id`, fmt.Sprintf("verapi-b-%d@example.test", time.Now().UnixNano())).Scan(&userB); err != nil {
		t.Fatalf("user b: %v", err)
	}

	storageSvc := storage.NewService(storage.NewLocalDriver(t.TempDir(), []byte("secret"), "https://files.example.test"), noopUsageReporter{}, "acme")
	cryptoSvc := dmscrypto.NewService(&fakeKEKProvider{kek: bytes.Repeat([]byte{0x55}, dmscrypto.KEKSize)})

	server := NewServer(pool, storageSvc, cryptoSvc, "acme", &OwnerChecker{Pool: pool})
	mux := http.NewServeMux()
	server.RegisterRoutes(mux)
	httpServer := httptest.NewServer(mux)
	t.Cleanup(httpServer.Close)

	return &testEnv{pool: pool, storage: storageSvc, crypto: cryptoSvc, server: httpServer}, userA, userB
}

func createDocumentWithRevision(t *testing.T, env *testEnv, userID, content string) string {
	t.Helper()
	ctx := context.Background()
	var documentID string
	if err := env.pool.QueryRow(ctx, `INSERT INTO documents (title, created_by) VALUES ('dok.pdf', $1) RETURNING id`, userID).Scan(&documentID); err != nil {
		t.Fatalf("dokument anlegen: %v", err)
	}
	sealEnv, err := env.crypto.Seal(ctx, "acme", strings.NewReader(content))
	if err != nil {
		t.Fatalf("seal: %v", err)
	}
	var buf bytes.Buffer
	_, _ = buf.ReadFrom(sealEnv.Ciphertext)
	key := storage.ObjectKey(documentID, "1")
	var revID string
	if err := env.pool.QueryRow(ctx, `
		INSERT INTO file_revisions (document_id, revision_number, storage_key, checksum_sha256, size_bytes, mime_type, created_by, wrapped_dek)
		VALUES ($1, 1, $2, 'x', $3, 'application/pdf', $4, $5) RETURNING id
	`, documentID, key, buf.Len(), userID, sealEnv.WrappedDEK).Scan(&revID); err != nil {
		t.Fatalf("revision anlegen: %v", err)
	}
	if _, err := env.pool.Exec(ctx, `UPDATE documents SET current_revision_id = $2 WHERE id = $1`, documentID, revID); err != nil {
		t.Fatalf("aktuelle revision setzen: %v", err)
	}
	if _, err := env.storage.Put(ctx, key, bytes.NewReader(buf.Bytes()), int64(buf.Len()), "application/octet-stream"); err != nil {
		t.Fatalf("objekt ablegen: %v", err)
	}
	return documentID
}

// Akzeptanzkriterium 1: Revisionen chronologisch mit Metadaten sichtbar.
func TestHandleList_ReturnsRevisionsChronologicallyWithMetadata(t *testing.T) {
	env, userA, _ := setupTest(t)
	doc := createDocumentWithRevision(t, env, userA, "inhalt")

	resp, err := http.Get(env.server.URL + "/documents/" + doc + "/revisions?caller=" + userA)
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	defer func() { _ = resp.Body.Close() }()
	var revisions []revisionDTO
	_ = json.NewDecoder(resp.Body).Decode(&revisions)
	if len(revisions) != 1 || revisions[0].CreatedBy != userA {
		t.Fatalf("erwartet 1 revision mit autor %q, habe: %+v", userA, revisions)
	}
}

// Akzeptanzkriterium/Pflichtpruefung 3: Berechtigung wird je Revision
// geprueft - userB (weder Dokument- noch Revisions-Ersteller) sieht die
// Revision als NICHT zugaenglich markiert und bekommt beim Content-Abruf
// 403.
func TestPermission_CheckedPerRevisionNotJustPerDocument(t *testing.T) {
	env, userA, userB := setupTest(t)
	doc := createDocumentWithRevision(t, env, userA, "geheim")

	resp, err := http.Get(env.server.URL + "/documents/" + doc + "/revisions?caller=" + userB)
	if err != nil {
		t.Fatalf("get (userB liste): %v", err)
	}
	defer func() { _ = resp.Body.Close() }()
	var revisions []revisionDTO
	_ = json.NewDecoder(resp.Body).Decode(&revisions)
	if len(revisions) != 1 || revisions[0].Accessible {
		t.Fatalf("userB haette die revision als NICHT zugaenglich sehen sollen: %+v", revisions)
	}

	contentResp, err := http.Get(env.server.URL + "/documents/" + doc + "/revisions/" + revisions[0].ID + "/content?caller=" + userB)
	if err != nil {
		t.Fatalf("get (userB content): %v", err)
	}
	defer func() { _ = contentResp.Body.Close() }()
	if contentResp.StatusCode != http.StatusForbidden {
		t.Fatalf("status = %d, want 403 fuer nicht-berechtigten aufrufer", contentResp.StatusCode)
	}

	// userA (ersteller) darf hingegen zugreifen.
	okResp, err := http.Get(env.server.URL + "/documents/" + doc + "/revisions/" + revisions[0].ID + "/content?caller=" + userA)
	if err != nil {
		t.Fatalf("get (userA content): %v", err)
	}
	defer func() { _ = okResp.Body.Close() }()
	if okResp.StatusCode != http.StatusOK {
		t.Fatalf("status = %d, want 200 fuer berechtigten aufrufer", okResp.StatusCode)
	}
	var buf bytes.Buffer
	_, _ = buf.ReadFrom(okResp.Body)
	if buf.String() != "geheim" {
		t.Fatalf("inhalt = %q, want 'geheim'", buf.String())
	}
}

// Akzeptanzkriterium 2: Wiederherstellung ueber die API erzeugt eine neue
// Revision.
func TestHandleRestore_CreatesNewRevisionViaAPI(t *testing.T) {
	env, userA, _ := setupTest(t)
	doc := createDocumentWithRevision(t, env, userA, "original")

	resp, err := http.Get(env.server.URL + "/documents/" + doc + "/revisions?caller=" + userA)
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	defer func() { _ = resp.Body.Close() }()
	var revisions []revisionDTO
	_ = json.NewDecoder(resp.Body).Decode(&revisions)

	restoreResp, err := http.Post(env.server.URL+"/documents/"+doc+"/revisions/"+revisions[0].ID+"/restore?caller="+userA, "application/json", nil)
	if err != nil {
		t.Fatalf("post restore: %v", err)
	}
	defer func() { _ = restoreResp.Body.Close() }()
	if restoreResp.StatusCode != http.StatusOK {
		body := new(bytes.Buffer)
		_, _ = body.ReadFrom(restoreResp.Body)
		t.Fatalf("status = %d, want 200: %s", restoreResp.StatusCode, body.String())
	}
	var restored revisionDTO
	_ = json.NewDecoder(restoreResp.Body).Decode(&restored)
	if restored.RevisionNumber != 2 {
		t.Fatalf("restore haette revision 2 erzeugen sollen, habe %d", restored.RevisionNumber)
	}

	all, err := versioning.ListRevisions(context.Background(), env.pool, doc)
	if err != nil {
		t.Fatalf("ListRevisions: %v", err)
	}
	if len(all) != 2 {
		t.Fatalf("erwartet 2 revisionen nach restore, habe %d", len(all))
	}
}

// VER-04 Akzeptanzkriterium 1: Revisionen sind frei zum Vergleich waehlbar
// (jedes beliebige Paar ueber den Diff-Endpunkt, nicht nur benachbarte).
func TestHandleDiff_ComparesFreelyChosenRevisions(t *testing.T) {
	env, userA, _ := setupTest(t)
	ctx := context.Background()
	doc := createDocumentWithRevision(t, env, userA, "Zeile 1\nZeile 2\nZeile 3")

	if _, err := versioning.CheckOut(ctx, env.pool, doc, userA, versioning.DefaultLeaseDuration); err != nil {
		t.Fatalf("checkout: %v", err)
	}
	if _, err := versioning.CheckIn(ctx, env.pool, env.storage, env.crypto, "acme", doc, userA, "zweite fassung", "text/plain", strings.NewReader("Zeile 1\nZeile 2 geaendert\nZeile 3\nZeile 4")); err != nil {
		t.Fatalf("checkin: %v", err)
	}

	all, err := versioning.ListRevisions(ctx, env.pool, doc)
	if err != nil || len(all) != 2 {
		t.Fatalf("ListRevisions: %v, %d", err, len(all))
	}

	resp, err := http.Get(env.server.URL + "/documents/" + doc + "/diff?caller=" + userA + "&from=" + all[0].ID + "&to=" + all[1].ID)
	if err != nil {
		t.Fatalf("get diff: %v", err)
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		body := new(bytes.Buffer)
		_, _ = body.ReadFrom(resp.Body)
		t.Fatalf("status = %d: %s", resp.StatusCode, body.String())
	}
	var got diffResponseDTO
	if err := json.NewDecoder(resp.Body).Decode(&got); err != nil {
		t.Fatalf("decode: %v", err)
	}

	var deletes, inserts int
	for _, op := range got.Text {
		switch op.Op {
		case "delete":
			deletes++
		case "insert":
			inserts++
		}
	}
	if deletes != 1 || inserts != 2 {
		t.Fatalf("erwartet 1 loeschung, 2 einfuegungen, habe deletes=%d inserts=%d: %+v", deletes, inserts, got.Text)
	}
	foundComment := false
	for _, d := range got.Metadata {
		if d.Field == "comment" && d.After == "zweite fassung" {
			foundComment = true
		}
	}
	if !foundComment {
		t.Fatalf("erwartete comment-metadatenaenderung nicht gefunden: %+v", got.Metadata)
	}
}

// Berechtigung wird fuer BEIDE Revisionen geprueft, nicht nur eine.
func TestHandleDiff_RequiresPermissionOnBothRevisions(t *testing.T) {
	env, userA, userB := setupTest(t)
	ctx := context.Background()
	doc := createDocumentWithRevision(t, env, userA, "geheim v1")

	if _, err := versioning.CheckOut(ctx, env.pool, doc, userA, versioning.DefaultLeaseDuration); err != nil {
		t.Fatalf("checkout: %v", err)
	}
	if _, err := versioning.CheckIn(ctx, env.pool, env.storage, env.crypto, "acme", doc, userA, "v2", "text/plain", strings.NewReader("geheim v2")); err != nil {
		t.Fatalf("checkin: %v", err)
	}
	all, err := versioning.ListRevisions(ctx, env.pool, doc)
	if err != nil || len(all) != 2 {
		t.Fatalf("ListRevisions: %v, %d", err, len(all))
	}

	resp, err := http.Get(env.server.URL + "/documents/" + doc + "/diff?caller=" + userB + "&from=" + all[0].ID + "&to=" + all[1].ID)
	if err != nil {
		t.Fatalf("get diff: %v", err)
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusForbidden {
		t.Fatalf("status = %d, want 403 fuer nicht-berechtigten aufrufer", resp.StatusCode)
	}
}