//go:build linux

package service

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"errors"
	"log"
	"net"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/aritmolab/thothii/tools/dwh-auth/internal/credential"
	"github.com/aritmolab/thothii/tools/dwh-auth/internal/record"
	"github.com/aritmolab/thothii/tools/dwh-auth/internal/registry"
)

const verifiedKeyIDHeader = "X-DWH-Key-ID"

func TestVerifyDecisionsAreFailClosedAndBodiesEmpty(t *testing.T) {
	store, closeStore := testStore(t)
	defer closeStore()
	valid, validRecord := testV1(t, 1)
	if err := store.Add(validRecord); err != nil {
		t.Fatalf("Add(valid) error = %v", err)
	}
	legacy := []byte("synthetic-legacy-secret")
	if err := store.Add(testLegacy(legacy)); err != nil {
		t.Fatalf("Add(legacy) error = %v", err)
	}
	expired, expiredRecord := testV1(t, 2)
	expiresAt := time.Date(2026, 8, 20, 11, 0, 0, 0, time.UTC)
	expiredRecord.ExpiresAt = &expiresAt
	if err := store.Add(expiredRecord); err != nil {
		t.Fatalf("Add(expired) error = %v", err)
	}
	revoked, revokedRecord := testV1(t, 3)
	if err := store.Add(revokedRecord); err != nil {
		t.Fatalf("Add(revoked) error = %v", err)
	}
	if err := store.Revoke(revokedRecord.KeyID, "synthetic", revokedRecord.CreatedAt.Add(time.Hour)); err != nil {
		t.Fatalf("Revoke() error = %v", err)
	}

	var logs bytes.Buffer
	handler := New(store, log.New(&logs, "", 0), func() time.Time {
		return time.Date(2026, 8, 20, 12, 0, 0, 0, time.UTC)
	})
	cases := []struct {
		name    string
		headers []string
		status  int
		keyID   string
		logCode string
	}{
		{name: "valid v1", headers: []string{string(valid)}, status: http.StatusNoContent, keyID: validRecord.KeyID, logCode: "allow_v1"},
		{name: "valid legacy", headers: []string{string(legacy)}, status: http.StatusNoContent, keyID: record.LegacyKeyID, logCode: "allow_legacy"},
		{name: "absent", status: http.StatusUnauthorized, logCode: "deny_header"},
		{name: "duplicate", headers: []string{string(valid), string(valid)}, status: http.StatusUnauthorized, logCode: "deny_header"},
		{name: "malformed", headers: []string{"thtdwh_v1.bad.bad"}, status: http.StatusUnauthorized, logCode: "deny_v1"},
		{name: "unknown", headers: []string{string(testUnknown(valid))}, status: http.StatusUnauthorized, logCode: "deny_unknown"},
		{name: "changed", headers: []string{string(testChanged(valid))}, status: http.StatusUnauthorized, logCode: "deny_mismatch"},
		{name: "expired", headers: []string{string(expired)}, status: http.StatusUnauthorized, logCode: "deny_unknown"},
		{name: "revoked", headers: []string{string(revoked)}, status: http.StatusUnauthorized, logCode: "deny_revoked"},
		{name: "oversized", headers: []string{strings.Repeat("a", credential.MaxHeaderBytes+1)}, status: http.StatusUnauthorized, logCode: "deny_header"},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			response := verifyRequest(handler, tc.headers...)
			if response.Code != tc.status {
				t.Fatalf("status = %d, want %d", response.Code, tc.status)
			}
			if response.Body.Len() != 0 {
				t.Fatalf("body = %q, want empty", response.Body.String())
			}
			if got := response.Header().Get(verifiedKeyIDHeader); got != tc.keyID {
				t.Fatalf("%s = %q, want %q", verifiedKeyIDHeader, got, tc.keyID)
			}
			if !strings.Contains(logs.String(), tc.logCode) {
				t.Fatalf("logs = %q, want decision %q", logs.String(), tc.logCode)
			}
		})
	}
	for _, forbidden := range []string{string(valid), string(legacy), validRecord.SecretSHA256, validRecord.Description, "query-secret"} {
		if strings.Contains(logs.String(), forbidden) {
			t.Fatalf("logs exposed forbidden value %q: %q", forbidden, logs.String())
		}
	}
	for _, line := range strings.Split(strings.TrimSpace(logs.String()), "\n") {
		fields := strings.Fields(line)
		if len(fields) != 2 && len(fields) != 3 {
			t.Fatalf("log fields = %q, want timestamp+decision with optional public ID", line)
		}
		if !strings.HasPrefix(fields[0], "timestamp=2026-08-20T12:00:00Z") || !strings.HasPrefix(fields[1], "decision=") {
			t.Fatalf("log line = %q, want timestamp and decision only", line)
		}
		if len(fields) == 3 && !strings.HasPrefix(fields[2], "key_id=") {
			t.Fatalf("log public field = %q, want key_id", line)
		}
	}
}

func TestVerifyMapsRegistryIntegrityFailuresToServiceUnavailable(t *testing.T) {
	root := t.TempDir()
	store, err := registry.Open(root)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	defer store.Close()
	value, item := testV1(t, 4)
	if err := store.Add(item); err != nil {
		t.Fatalf("Add() error = %v", err)
	}
	if err := os.Chmod(filepath.Join(root, "active", item.KeyID+".json"), 0o660); err != nil {
		t.Fatalf("Chmod() error = %v", err)
	}
	response := verifyRequest(New(store, log.New(&bytes.Buffer{}, "", 0), time.Now), string(value))
	if response.Code != http.StatusServiceUnavailable || response.Body.Len() != 0 {
		t.Fatalf("integrity response = (%d, %q), want (503, empty)", response.Code, response.Body.String())
	}
}

func TestVerifyFailsClosedWhenUnrelatedRegistryRecordIsCorrupt(t *testing.T) {
	root := t.TempDir()
	store, err := registry.Open(root)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	defer store.Close()
	value, item := testV1(t, 5)
	if err := store.Add(item); err != nil {
		t.Fatalf("Add() error = %v", err)
	}
	_, corrupt := testV1(t, 6)
	path := filepath.Join(root, "active", corrupt.KeyID+".json")
	if err := os.WriteFile(path, []byte(`{"schema_version":`), 0o640); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	if err := os.Chmod(path, 0o640); err != nil {
		t.Fatalf("Chmod() error = %v", err)
	}
	response := verifyRequest(New(store, log.New(&bytes.Buffer{}, "", 0), time.Now), string(value))
	if response.Code != http.StatusServiceUnavailable || response.Body.Len() != 0 {
		t.Fatalf("unrelated corrupt record response = (%d, %q), want (503, empty)", response.Code, response.Body.String())
	}
}

func TestVerifyFailsClosedWhenActiveAndRevokedLegacyRecordsCoexist(t *testing.T) {
	root := t.TempDir()
	store, err := registry.Open(root)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	defer store.Close()
	legacyValue := []byte("synthetic-legacy-secret")
	legacy := testLegacy(legacyValue)
	if err := store.Add(legacy); err != nil {
		t.Fatalf("Add() error = %v", err)
	}
	revokedAt := legacy.CreatedAt.Add(time.Hour)
	legacy.RevokedAt = &revokedAt
	legacy.RevocationReason = "synthetic"
	data, err := json.Marshal(legacy)
	if err != nil {
		t.Fatalf("Marshal() error = %v", err)
	}
	data = append(data, '\n')
	path := filepath.Join(root, "revoked", record.LegacyKeyID+".json")
	if err := os.WriteFile(path, data, 0o640); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	if err := os.Chmod(path, 0o640); err != nil {
		t.Fatalf("Chmod() error = %v", err)
	}
	response := verifyRequest(New(store, log.New(&bytes.Buffer{}, "", 0), time.Now), string(legacyValue))
	if response.Code != http.StatusServiceUnavailable || response.Body.Len() != 0 {
		t.Fatalf("multiple legacy response = (%d, %q), want (503, empty)", response.Code, response.Body.String())
	}
}

func TestVerifyMapsMultipleLegacyRecordsToServiceUnavailable(t *testing.T) {
	root := t.TempDir()
	store, err := registry.Open(root)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	defer store.Close()
	legacy := testLegacy([]byte("synthetic-legacy-secret"))
	if err := store.Add(legacy); err != nil {
		t.Fatalf("Add() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(root, "active", "duplicate.json"), []byte(`{"schema_version":1}`), 0o640); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	if err := os.Chmod(filepath.Join(root, "active", "duplicate.json"), 0o640); err != nil {
		t.Fatalf("Chmod() error = %v", err)
	}
	response := verifyRequest(New(store, log.New(&bytes.Buffer{}, "", 0), time.Now), "synthetic-legacy-secret")
	if response.Code != http.StatusServiceUnavailable || response.Body.Len() != 0 {
		t.Fatalf("multiple legacy response = (%d, %q), want (503, empty)", response.Code, response.Body.String())
	}
}

func TestListenAndServeFailsClosedForInvalidPathsAndCollisions(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	parent := t.TempDir()
	for _, tc := range []struct {
		name, registryRoot, socket string
		setup                      func(string)
	}{
		{name: "noncanonical registry root", registryRoot: root + "/.", socket: filepath.Join(parent, "verify.sock")},
		{name: "noncanonical socket", registryRoot: root, socket: parent + "/./verify.sock"},
		{name: "regular collision", registryRoot: root, socket: filepath.Join(parent, "regular.sock"), setup: func(path string) {
			if err := os.WriteFile(path, []byte("do not remove"), 0o600); err != nil {
				t.Fatal(err)
			}
		}},
		{name: "directory collision", registryRoot: root, socket: filepath.Join(parent, "directory.sock"), setup: func(path string) {
			if err := os.Mkdir(path, 0o700); err != nil {
				t.Fatal(err)
			}
		}},
		{name: "symlink collision", registryRoot: root, socket: filepath.Join(parent, "symlink.sock"), setup: func(path string) {
			if err := os.Symlink(filepath.Join(parent, "target.sock"), path); err != nil {
				t.Fatal(err)
			}
		}},
	} {
		t.Run(tc.name, func(t *testing.T) {
			if tc.setup != nil {
				tc.setup(tc.socket)
			}
			err := ListenAndServe(context.Background(), Config{RegistryRoot: tc.registryRoot, Socket: tc.socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
			if err == nil {
				t.Fatal("ListenAndServe() error = nil, want fail-closed refusal")
			}
			if tc.setup != nil {
				if _, statErr := os.Lstat(tc.socket); statErr != nil {
					t.Fatalf("collision was removed: %v", statErr)
				}
			}
		})
	}
}

func TestListenAndServeRejectsUnsafeSocketParents(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	for _, mode := range []os.FileMode{0o770, 0o702} {
		t.Run("mode "+mode.String(), func(t *testing.T) {
			parent := t.TempDir()
			if err := os.Chmod(parent, mode); err != nil {
				t.Fatalf("Chmod(%v) error = %v", mode, err)
			}
			socket := filepath.Join(parent, "verify.sock")
			err := ListenAndServe(context.Background(), Config{RegistryRoot: root, Socket: socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
			if err == nil {
				t.Fatalf("ListenAndServe(parent mode %v) error = nil, want refusal", mode)
			}
			if _, err := os.Lstat(socket); !errors.Is(err, os.ErrNotExist) {
				t.Fatalf("unsafe parent created socket: %v", err)
			}
		})
	}
}

func TestListenAndServeRejectsForeignOwnedSocketParent(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	parent := t.TempDir()
	socket := filepath.Join(parent, "verify.sock")
	previous := socketParentOwner
	t.Cleanup(func() { socketParentOwner = previous })
	socketParentOwner = func(string) (uint32, error) { return uint32(os.Geteuid()) + 1, nil }
	err := ListenAndServe(context.Background(), Config{RegistryRoot: root, Socket: socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
	if err == nil {
		t.Fatal("ListenAndServe() error = nil, want foreign-parent refusal")
	}
	if _, err := os.Lstat(socket); !errors.Is(err, os.ErrNotExist) {
		t.Fatalf("foreign parent created socket: %v", err)
	}
}

func TestListenAndServeReclaimsOnlyOwnedStaleSocketAndCleansUpOnCancellation(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	socket := filepath.Join(t.TempDir(), "verify.sock")
	stale, err := net.ListenUnix("unix", &net.UnixAddr{Name: socket, Net: "unix"})
	if err != nil {
		t.Fatalf("ListenUnix() error = %v", err)
	}
	stale.SetUnlinkOnClose(false)
	if err := stale.Close(); err != nil {
		t.Fatalf("Close(stale) error = %v", err)
	}
	if info, err := os.Lstat(socket); err != nil || info.Mode()&os.ModeSocket == 0 {
		t.Fatalf("stale socket = (%v, %v), want socket", info, err)
	}
	ctx, cancel := context.WithCancel(context.Background())
	errs := make(chan error, 1)
	go func() {
		errs <- ListenAndServe(ctx, Config{RegistryRoot: root, Socket: socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
	}()
	waitForReadySocket(t, socket)
	info, err := os.Stat(socket)
	if err != nil {
		t.Fatalf("Stat(socket) error = %v", err)
	}
	if got, want := info.Mode().Perm(), os.FileMode(0o660); got != want {
		t.Fatalf("socket mode = %04o, want %04o", got, want)
	}
	cancel()
	if err := <-errs; err != nil {
		t.Fatalf("ListenAndServe() error = %v", err)
	}
	if _, err := os.Lstat(socket); !errors.Is(err, os.ErrNotExist) {
		t.Fatalf("socket after cancellation = %v, want removal", err)
	}
}

func TestListenAndServeRefusesStaleSocketWithForeignOwner(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	socket := filepath.Join(t.TempDir(), "verify.sock")
	stale, err := net.ListenUnix("unix", &net.UnixAddr{Name: socket, Net: "unix"})
	if err != nil {
		t.Fatalf("ListenUnix() error = %v", err)
	}
	stale.SetUnlinkOnClose(false)
	if err := stale.Close(); err != nil {
		t.Fatalf("Close(stale) error = %v", err)
	}
	previous := socketOwner
	socketOwner = func(string) (uint32, error) { return uint32(os.Geteuid()) + 1, nil }
	defer func() { socketOwner = previous }()
	err = ListenAndServe(context.Background(), Config{RegistryRoot: root, Socket: socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
	if err == nil {
		t.Fatal("ListenAndServe() error = nil, want foreign-owner refusal")
	}
	if _, err := os.Lstat(socket); err != nil {
		t.Fatalf("foreign socket was removed: %v", err)
	}
}

func TestListenAndServeRefusesLiveSocket(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	socket := filepath.Join(t.TempDir(), "verify.sock")
	live, err := net.ListenUnix("unix", &net.UnixAddr{Name: socket, Net: "unix"})
	if err != nil {
		t.Fatalf("ListenUnix() error = %v", err)
	}
	defer live.Close()
	err = ListenAndServe(context.Background(), Config{RegistryRoot: root, Socket: socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
	if err == nil {
		t.Fatal("ListenAndServe() error = nil, want live-socket refusal")
	}
	if info, statErr := os.Lstat(socket); statErr != nil || info.Mode()&os.ModeSocket == 0 {
		t.Fatalf("live socket was changed: (%v, %v)", info, statErr)
	}
}

func TestListenAndServeCleanupRefusesChangedSocketPath(t *testing.T) {
	root := t.TempDir()
	initializeRegistry(t, root)
	socket := filepath.Join(t.TempDir(), "verify.sock")
	ctx, cancel := context.WithCancel(context.Background())
	errs := make(chan error, 1)
	go func() {
		errs <- ListenAndServe(ctx, Config{RegistryRoot: root, Socket: socket, Logger: log.New(&bytes.Buffer{}, "", 0), Now: time.Now})
	}()
	waitForReadySocket(t, socket)
	previous := socketOwner
	swapped := false
	t.Cleanup(func() { socketOwner = previous })
	socketOwner = func(path string) (uint32, error) {
		if !swapped {
			swapped = true
			if err := os.Remove(path); err != nil {
				return 0, err
			}
			if err := os.WriteFile(path, []byte("replacement"), 0o600); err != nil {
				return 0, err
			}
		}
		return uint32(os.Geteuid()), nil
	}
	cancel()
	err := <-errs
	if err == nil {
		t.Fatal("ListenAndServe() error = nil, want changed-path refusal")
	}
	value, readErr := os.ReadFile(socket)
	if readErr != nil || string(value) != "replacement" {
		t.Fatalf("replacement after cleanup = (%q, %v), want retained regular file", value, readErr)
	}
}

func initializeRegistry(t *testing.T, root string) {
	t.Helper()
	store, err := registry.Open(root)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	if err := store.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
}

func waitForReadySocket(t *testing.T, socket string) {
	t.Helper()
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if info, err := os.Lstat(socket); err == nil && info.Mode()&os.ModeSocket != 0 && info.Mode().Perm() == 0o660 {
			return
		}
		time.Sleep(5 * time.Millisecond)
	}
	t.Fatalf("socket %q did not become ready with mode 0660", socket)
}

func TestVerifyRejectsOtherPathsAndMethodsWithEmptyBodies(t *testing.T) {
	store, closeStore := testStore(t)
	defer closeStore()
	handler := New(store, log.New(&bytes.Buffer{}, "", 0), time.Now)
	for _, tc := range []struct {
		method string
		path   string
		status int
	}{
		{method: http.MethodGet, path: "/other", status: http.StatusNotFound},
		{method: http.MethodPost, path: "/verify", status: http.StatusMethodNotAllowed},
	} {
		t.Run(tc.method+tc.path, func(t *testing.T) {
			request := httptest.NewRequest(tc.method, tc.path, nil)
			response := httptest.NewRecorder()
			handler.ServeHTTP(response, request)
			if response.Code != tc.status || response.Body.Len() != 0 {
				t.Fatalf("response = (%d, %q), want (%d, empty)", response.Code, response.Body.String(), tc.status)
			}
		})
	}
}

func verifyRequest(handler http.Handler, values ...string) *httptest.ResponseRecorder {
	request := httptest.NewRequest(http.MethodGet, "/verify?credential=query-secret", nil)
	for _, value := range values {
		request.Header.Add("X-API-Key", value)
	}
	response := httptest.NewRecorder()
	handler.ServeHTTP(response, request)
	return response
}

func testStore(t *testing.T) (*registry.Store, func()) {
	t.Helper()
	store, err := registry.Open(t.TempDir())
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	return store, func() {
		if err := store.Close(); err != nil {
			t.Fatalf("Close() error = %v", err)
		}
	}
}

func testV1(t *testing.T, seed byte) ([]byte, record.Record) {
	t.Helper()
	material, err := credential.Generate(bytes.NewReader(bytes.Repeat([]byte{seed}, 44)))
	if err != nil {
		t.Fatalf("Generate() error = %v", err)
	}
	return material.Value, record.Record{
		SchemaVersion:  record.SchemaVersion,
		Kind:           record.KindV1,
		KeyID:          material.KeyID,
		InstallationID: "test-installation",
		Description:    "synthetic description",
		SecretSHA256:   base64.RawURLEncoding.EncodeToString(material.Digest[:]),
		CreatedAt:      time.Date(2026, 8, 20, 10, 0, int(seed), 0, time.UTC),
	}
}

func testLegacy(value []byte) record.Record {
	digest := sha256.Sum256(value)
	return record.Record{
		SchemaVersion:  record.SchemaVersion,
		Kind:           record.KindLegacyRaw,
		KeyID:          record.LegacyKeyID,
		InstallationID: record.LegacyKeyID,
		Description:    "legacy synthetic description",
		SecretSHA256:   base64.RawURLEncoding.EncodeToString(digest[:]),
		CreatedAt:      time.Date(2026, 8, 20, 10, 0, 0, 0, time.UTC),
	}
}

func testChanged(value []byte) []byte {
	changed := append([]byte(nil), value...)
	changed[len(credential.Prefix)+1+credential.KeyIDEncodedLength+1] = 'B'
	return changed
}

func testUnknown(value []byte) []byte {
	unknown := append([]byte(nil), value...)
	unknown[len(credential.Prefix)+1] = 'B'
	return unknown
}