// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package postgres

import (
	"database/sql"
	"fmt"
	"slices"
	"testing"

	"github.com/google/go-cmp/cmp"
	"golang.org/x/mod/semver"
	"golang.org/x/pkgsite/internal"
	"golang.org/x/pkgsite/internal/source"
	"golang.org/x/pkgsite/internal/stdlib"
	"golang.org/x/pkgsite/internal/testing/sample"
	"golang.org/x/pkgsite/internal/version"
)

func TestGetVersionsForPath(t *testing.T) {
	t.Parallel()
	var (
		taggedAndPseudoModule = "path.to/foo"
		taggedModuleV2        = "path.to/foo/v2"
		taggedModuleV3        = "path.to/foo/v3"
		pseudoModule          = "golang.org/x/tools"
		otherModule           = "path.to/other"
		incompatibleModule    = "path.to/incompatible"
		rootModule            = "golang.org/foo/bar"
		nestedModule          = "golang.org/foo/bar/api"
		testModules           = []*internal.Module{
			sample.Module(stdlib.ModulePath, "v1.15.0-beta.1", "cmd/go"),
			sample.Module(stdlib.ModulePath, "v1.14.6", "cmd/go"),
			sample.Module(taggedModuleV3, "v3.2.0-beta", "bar"),
			sample.Module(taggedModuleV3, "v3.2.0-alpha.2", "bar"),
			sample.Module(taggedModuleV3, "v3.2.0-alpha.1", "bar"),
			sample.Module(taggedModuleV3, "v3.1.0", "bar"),
			sample.Module(taggedModuleV3, "v3.0.0", "bar"),
			sample.Module(taggedModuleV2, "v2.0.1", "bar"),
			sample.Module(taggedAndPseudoModule, "v1.5.3-pre1", "bar"),
			sample.Module(taggedAndPseudoModule, "v1.5.2", "bar"),
			sample.Module(taggedAndPseudoModule, "v0.0.0-20200101120000-000000000000", "bar"),
			sample.Module(otherModule, "v3.0.0", "thing"),
			sample.Module(incompatibleModule, "v2.0.0+incompatible", "module"),
			sample.Module(incompatibleModule, "v0.0.0", "module"),
			sample.Module(rootModule, "v1.0.3", "api"),
			sample.Module(rootModule, "v0.11.6", "api"),
			sample.Module(nestedModule, "v1.0.4", "api"),
			sample.Module(nestedModule, "v1.0.3", "api"),
		}
	)

	// Add 12 pseudo versions to the test modules. Below we only
	// expect to return the 10 most recent.
	for i := 1; i <= 12; i++ {
		testModules = append(testModules, sample.Module(pseudoModule, fmt.Sprintf("v0.0.0-202001011200%02d-000000000000", i), "blog"))
	}

	testDB, release := acquire(t)
	defer release()

	for _, m := range testModules {
		goMod := "module " + m.ModulePath
		if m.ModulePath == rootModule {
			goMod = `
				module golang.org/foo/bar // Deprecated: use other
				retract v1.0.3 // security flaw
			`
		}
		testDB.MustInsertModuleGoMod(t.Context(), t, m, goMod)
	}

	stdModuleVersions := []*internal.ModuleInfo{
		{
			ModulePath: stdlib.ModulePath,
			Version:    "v1.15.0-beta.1",
		},
		{
			ModulePath: stdlib.ModulePath,
			Version:    "v1.14.6",
		},
	}

	fooModuleVersions := []*internal.ModuleInfo{
		{
			ModulePath: taggedModuleV3,
			Version:    "v3.2.0-beta",
		},
		{
			ModulePath: taggedModuleV3,
			Version:    "v3.2.0-alpha.2",
		},
		{
			ModulePath: taggedModuleV3,
			Version:    "v3.2.0-alpha.1",
		},
		{
			ModulePath: taggedModuleV3,
			Version:    "v3.1.0",
		},
		{
			ModulePath: taggedModuleV3,
			Version:    "v3.0.0",
		},
		{
			ModulePath: taggedModuleV2,
			Version:    "v2.0.1",
		},
		{
			ModulePath: taggedAndPseudoModule,
			Version:    "v1.5.3-pre1",
		},
		{
			ModulePath: taggedAndPseudoModule,
			Version:    "v1.5.2",
		},
	}

	testCases := []struct {
		name, path string
		want       []*internal.ModuleInfo
	}{
		{
			name: "std_module",
			path: stdlib.ModulePath,
			want: stdModuleVersions,
		},
		{
			name: "stdlib_path",
			path: "cmd",
			want: stdModuleVersions,
		},
		{
			name: "stdlib_package",
			path: "cmd/go",
			want: stdModuleVersions,
		},
		{
			name: "want_tagged_versions_only",
			path: "path.to/foo/bar",
			want: fooModuleVersions,
		},
		{
			name: "want_all_tagged_versions_at_v2_path",
			path: "path.to/foo/v2/bar",
			want: fooModuleVersions,
		},
		{
			name: "want_pseudo_versions_only",
			path: "golang.org/x/tools/blog",
			want: func() []*internal.ModuleInfo {
				versions := []*internal.ModuleInfo{}
				// Expect the 10 most recent in DESC order
				for i := 12; i > 2; i-- {
					versions = append(versions, &internal.ModuleInfo{
						ModulePath: pseudoModule,
						Version:    fmt.Sprintf("v0.0.0-202001011200%02d-000000000000", i),
					})
				}
				return versions
			}(),
		},
		{
			name: "want_tagged_versions_includes_incompatible",
			path: "path.to/incompatible/module",
			want: []*internal.ModuleInfo{
				{
					ModulePath: incompatibleModule,
					Version:    "v0.0.0",
				},
				{
					ModulePath: incompatibleModule,
					Version:    "v2.0.0+incompatible",
				},
			},
		},
		{
			name: "nested_module_path",
			path: "golang.org/foo/bar/api",
			want: []*internal.ModuleInfo{
				{
					ModulePath: nestedModule,
					Version:    "v1.0.4",
				},
				{
					ModulePath: nestedModule,
					Version:    "v1.0.3",
				},
				{
					ModulePath:          rootModule,
					Version:             "v1.0.3",
					Deprecated:          true,
					DeprecationComment:  "use other",
					Retracted:           true,
					RetractionRationale: "security flaw",
				},
				{
					ModulePath:         rootModule,
					Version:            "v0.11.6",
					Deprecated:         true,
					DeprecationComment: "use other",
				},
			},
		},
		{
			name: "root module path",
			path: "golang.org/foo/bar",
			want: []*internal.ModuleInfo{
				{
					ModulePath:          rootModule,
					Version:             "v1.0.3",
					Deprecated:          true,
					DeprecationComment:  "use other",
					Retracted:           true,
					RetractionRationale: "security flaw",
				},
				{
					ModulePath:         rootModule,
					Version:            "v0.11.6",
					Deprecated:         true,
					DeprecationComment: "use other",
				},
			},
		},
		{
			name: "want_zero_results_in_non_empty_db",
			path: "not.a/real/path",
		},
	}

	latestVersions := map[string]string{
		stdlib.ModulePath:     "v1.14.6", // v1.15.0-beta.1 is pre-release
		taggedModuleV3:        "v3.1.0",  // v3.2.0-beta is pre-release
		taggedModuleV2:        "v2.0.1",
		taggedAndPseudoModule: "v1.5.2", // v1.5.3-pre1 is pre-release
		pseudoModule:          "v0.0.0-20200101120012-000000000000",
		otherModule:           "v3.0.0",
		incompatibleModule:    "v0.0.0", // v2.0.0+incompatible is incompatible
		rootModule:            "v0.11.6",
		nestedModule:          "v1.0.4",
	}

	for _, test := range testCases {
		t.Run(test.name, func(t *testing.T) {
			for _, w := range test.want {
				mod := sample.ModuleInfo(w.ModulePath, w.Version)
				w.CommitTime = mod.CommitTime
				w.IsRedistributable = mod.IsRedistributable
				w.HasGoMod = mod.HasGoMod
				w.SourceInfo = mod.SourceInfo
				w.LatestVersion = latestVersions[w.ModulePath]
			}

			got, err := testDB.GetVersionsForPath(t.Context(), test.path)
			if err != nil {
				t.Fatal(err)
			}
			if diff := cmp.Diff(test.want, got,
				cmp.AllowUnexported(source.Info{}),
			); diff != "" {
				t.Errorf("testDB.GetVersionsForPath(%q) mismatch (-want +got):\n%s", test.path, diff)
			}
		})
	}
}

func TestGetPathVersionsSorting(t *testing.T) {
	// Validate that getPathVersions sorts by version,
	// then by module path, with incompatible versions last.
	testDB, release := acquire(t)
	defer release()
	testModules := []*internal.Module{
		sample.Module("m.com/a", "v1.0.0", "pkg"),
		sample.Module("m.com/a", "v1.2.3", "pkg"),
		sample.Module("m.com/a", "v1.2.3-pre", "pkg"),
		sample.Module("m.com/a", "v2.1.1+incompatible", "pkg"),
		sample.Module("m.com/a", "v2.2.2+incompatible", "pkg"),
		sample.Module("m.com/a", "v0.0.0-20200101120012-000000000000", "pkg"),
		sample.Module("m.com/a/v2", "v2.2.2", "pkg"),
		sample.Module("m.com/a/v2", "v2.1.1", "pkg"),
		sample.Module("m.com/a/v11", "v11.0.0", "pkg"),
		// same package path, different module
		sample.Module("m.com", "v1.2.3", "a/pkg"),
		sample.Module("m.com", "v1.3.0", "a/pkg"),
	}
	for _, m := range testModules {
		testDB.MustInsertModule(t, m)
	}
	gotmods, _, err := testDB.GetPathVersions(t.Context(), "m.com/a", "", 0, version.TypePrerelease, version.TypeRelease, version.TypePseudo)
	if err != nil {
		t.Fatal(err)
	}

	type modver struct {
		ModulePath, Version string
	}
	want := []modver{
		{"m.com/a/v11", "v11.0.0"},
		{"m.com/a/v2", "v2.2.2"},
		{"m.com/a/v2", "v2.1.1"},
		{"m.com", "v1.3.0"},
		// version ties are broken by module path
		{"m.com/a", "v1.2.3"},
		{"m.com", "v1.2.3"},
		{"m.com/a", "v1.2.3-pre"},
		{"m.com/a", "v1.0.0"},
		{"m.com/a", "v0.0.0-20200101120012-000000000000"},
		{"m.com/a", "v2.2.2+incompatible"},
		{"m.com/a", "v2.1.1+incompatible"},
	}
	var got []modver
	for _, mi := range gotmods {
		got = append(got, modver{mi.ModulePath, mi.Version})
	}
	if diff := cmp.Diff(want, got); diff != "" {
		t.Errorf("mismatch (-want, +got):\n%s", diff)
	}
}

func TestGetLatestInfo(t *testing.T) {
	t.Parallel()
	testDB, release := acquire(t)
	defer release()

	for _, m := range []*internal.Module{
		sample.Module("a.com/M", "v99.0.0+incompatible", "all", "most"),
		sample.Module("a.com/M", "v1.1.1", "all", "most", "some", "one", "D/other"),
		sample.Module("a.com/M", "v1.2.0", "all", "most"),
		sample.Module("a.com/M/v2", "v2.0.5", "all", "most"),
		sample.Module("a.com/M/v3", "v3.0.1", "all", "some"),
		sample.Module("a.com/M/D", "v1.3.0", "other"),
		sample.Module("b.com/M/v9", "v9.0.0", ""),
		sample.Module("b.com/M/v10", "v10.0.0", ""),
		sample.Module("gopkg.in/M.v1", "v1.0.0", ""),
		sample.Module("gopkg.in/M.v2", "v2.0.0-pre", ""),
		sample.Module("gopkg.in/M.v3", "v3.0.0-20200602140019-6ec2bf8d378b", ""),
		sample.Module("c.com/M", "v0.0.0-20200602140019-6ec2bf8d378b", ""),
	} {
		testDB.MustInsertModule(t, m)
	}

	for _, test := range []struct {
		unit, module string
		want         internal.LatestInfo
	}{
		{
			// A unit that is the module.
			"a.com/M", "a.com/M",

			internal.LatestInfo{
				MinorVersion:      "v1.2.0",
				MinorModulePath:   "a.com/M",
				UnitExistsAtMinor: true,
				MajorModulePath:   "a.com/M/v3",
				MajorUnitPath:     "a.com/M/v3",
			},
		},
		{
			// A unit that exists in all versions of the module.
			"a.com/M/all", "a.com/M",

			internal.LatestInfo{
				MinorVersion:      "v1.2.0",
				MinorModulePath:   "a.com/M",
				UnitExistsAtMinor: true,
				MajorModulePath:   "a.com/M/v3",
				MajorUnitPath:     "a.com/M/v3/all",
			},
		},
		{
			// A unit that exists in most versions, but not the latest major.
			"a.com/M/most", "a.com/M",

			internal.LatestInfo{
				MinorVersion:      "v1.2.0",
				MinorModulePath:   "a.com/M",
				UnitExistsAtMinor: true,
				MajorModulePath:   "a.com/M/v3",
				MajorUnitPath:     "a.com/M/v3",
			},
		},
		{
			// A unit that does not exist at the latest minor version, but does at the latest major.
			"a.com/M/some", "a.com/M",

			internal.LatestInfo{
				MinorVersion:      "v1.1.1",
				MinorModulePath:   "a.com/M",
				UnitExistsAtMinor: false,
				MajorModulePath:   "a.com/M/v3",
				MajorUnitPath:     "a.com/M/v3/some",
			},
		},
		{
			// A unit that does not exist at the latest minor or major versions.
			"a.com/M/one", "a.com/M",

			internal.LatestInfo{
				MinorVersion:      "v1.1.1",
				MinorModulePath:   "a.com/M",
				UnitExistsAtMinor: false,
				MajorModulePath:   "a.com/M/v3",
				MajorUnitPath:     "a.com/M/v3",
			},
		},
		{
			// A unit whose latest minor version is in a different module.
			"a.com/M/D/other", "a.com/M",

			internal.LatestInfo{
				MinorVersion:      "v1.3.0",
				MinorModulePath:   "a.com/M/D",
				UnitExistsAtMinor: false,
				MajorModulePath:   "a.com/M/v3",
				MajorUnitPath:     "a.com/M/v3",
			},
		},
		{
			// A module with v9 and v10 versions.
			"b.com/M/v9", "b.com/M/v9",
			internal.LatestInfo{
				MinorVersion:      "v9.0.0",
				MinorModulePath:   "b.com/M/v9",
				UnitExistsAtMinor: true,
				MajorModulePath:   "b.com/M/v10",
				MajorUnitPath:     "b.com/M/v10",
			},
		},
		{
			// gopkg.in module, highest version is not tagged
			"gopkg.in/M.v1", "gopkg.in/M.v1",
			internal.LatestInfo{
				MinorVersion:      "v1.0.0",
				MinorModulePath:   "gopkg.in/M.v1",
				UnitExistsAtMinor: true,
				MajorModulePath:   "gopkg.in/M.v2",
				MajorUnitPath:     "gopkg.in/M.v2",
			},
		},
		{
			// no tagged versions
			"c.com/M", "c.com/M",
			internal.LatestInfo{
				MinorVersion:      "v0.0.0-20200602140019-6ec2bf8d378b",
				MinorModulePath:   "c.com/M",
				UnitExistsAtMinor: true,
				MajorModulePath:   "",
				MajorUnitPath:     "",
			},
		},
	} {
		t.Run(test.unit, func(t *testing.T) {
			got, err := testDB.GetLatestInfo(t.Context(), test.unit, test.module, nil)
			if err != nil {
				t.Fatal(err)
			}
			if diff := cmp.Diff(test.want, got); diff != "" {
				t.Errorf("mismatch (-want, +got):\n%s", diff)
			}
		})
	}
}

func TestRawIsMoreRecent(t *testing.T) {
	for _, test := range []struct {
		new, cur string
		want     bool
	}{
		{"v1.2.0", "v1.0.0", true},
		{"v1.2.0", "v1.2.0", false},
		{"v1.2.0", "v1.3.0", false},
		{"v1.0.0", "v1.9.9-pre", true},          // release beats prerelease
		{"v1.0.0", "v2.3.4+incompatible", true}, // compatible beats incompatible
	} {
		got := rawIsMoreRecent(test.new, test.cur)
		if got != test.want {
			t.Errorf("rawIsMoreRecent(%q, %q) = %t, want %t", test.new, test.cur, got, test.want)
		}
	}
}

func TestGetLatestGoodVersion(t *testing.T) {
	t.Parallel()
	testDB, release := acquire(t)
	defer release()

	const (
		modulePath = "example.com/m"
		modFile    = `
			module example.com/m
			retract v1.3.0
		`
	)

	lmv, err := internal.NewLatestModuleVersions(modulePath, "", "", "", []byte(modFile))
	if err != nil {
		t.Fatal(err)
	}
	for _, v := range []string{"v2.0.0+incompatible", "v1.4.0-pre", "v1.3.0", "v1.2.0", "v1.1.0"} {
		testDB.MustInsertModule(t, sample.Module(modulePath, v, "pkg"))
	}

	for _, test := range []struct {
		name   string
		cooked string // cooked latest version; empty means nil lmv
		want   string
	}{
		{
			name:   "compatible",
			cooked: "v1.3.0",
			want:   "v1.2.0", // v1.3.0 is retracted
		},
		{
			name:   "incompatible",
			cooked: "v2.0.0+incompatible",
			want:   "v2.0.0+incompatible",
		},
		{
			name:   "bad", // cooked version not in modules table
			cooked: "v1.4.0",
			want:   "v1.2.0",
		},
		{
			name:   "nil",
			cooked: "", // no latest-version info
			want:   "v2.0.0+incompatible",
		},
	} {
		t.Run(test.name, func(t *testing.T) {
			var lm *internal.LatestModuleVersions
			if test.cooked != "" {
				lmv.CookedVersion = test.cooked
				lm = lmv
			}
			got, err := getLatestGoodVersion(t.Context(), testDB.db, modulePath, lm)
			if err != nil {
				t.Fatal(err)
			}
			if got != test.want {
				t.Errorf("got %q, want %q", got, test.want)
			}
		})
	}
}

func TestLatestModuleVersions(t *testing.T) {
	t.Parallel()
	testDB, release := acquire(t)
	defer release()

	const (
		modulePath = "example.com/m"
		modFile    = `
			module example.com/m
			retract v1.3.0
		`
		incompatible = "v2.0.0+incompatible"
	)
	modBytes := []byte(modFile)

	type versions struct {
		raw, cooked string
	}
	// These tests form a sequence. Each test's want versions are in the DB for the next test.
	for _, test := range []struct {
		name     string
		in, want versions
	}{
		{
			name: "initial",
			in:   versions{"v1.3.0", "v1.2.0"},
			want: versions{"v1.3.0", "v1.2.0"},
		},
		{
			name: "older", // older incoming info doesn't cause an update
			in:   versions{"v1.2.0", "v1.2.0"},
			want: versions{"v1.3.0", "v1.2.0"},
		},
		{
			name: "newer bad", // a newer version, not in modules table
			in:   versions{"v1.4.0", "v1.4.0"},
			want: versions{"v1.4.0", "v1.4.0"},
		},
		{
			name: "incompatible",
			in:   versions{incompatible, incompatible},
			want: versions{incompatible, incompatible},
		},
		{
			name: "compatible", // "downgrade" from incompatible to compatible will update
			in:   versions{"v1.3.0", "v1.2.0"},
			want: versions{"v1.3.0", "v1.2.0"},
		},
	} {
		t.Run(test.name, func(t *testing.T) {
			vNew, err := internal.NewLatestModuleVersions(modulePath, test.in.raw, test.in.cooked, "", modBytes)
			if err != nil {
				t.Fatal(err)
			}
			vGot, err := testDB.UpdateLatestModuleVersions(t.Context(), vNew)
			if err != nil {
				t.Fatal(err)
			}
			if vGot == nil {
				t.Fatal("got nothing")
			}
			got := versions{vGot.RawVersion, vGot.CookedVersion}
			if got != test.want {
				t.Fatalf("got %q, want %q", got, test.want)
			}
		})
	}
}

func TestLatestModuleVersionsBadStatus(t *testing.T) {
	t.Parallel()
	testDB, release := acquire(t)
	defer release()

	const modulePath = "example.com/m"

	getStatus := func() int {
		var s int
		err := testDB.db.QueryRow(t.Context(), `
				SELECT status
				FROM latest_module_versions l
				INNER JOIN paths p ON (p.id=l.module_path_id)
				WHERE p.path = $1`,
			modulePath).Scan(&s)
		if err != nil && err != sql.ErrNoRows {
			t.Fatal(err)
		}
		return s
	}

	// Insert a failure status.
	newStatus := 410
	if err := testDB.UpdateLatestModuleVersionsStatus(t.Context(), modulePath, newStatus); err != nil {
		t.Fatal(err)
	}
	if got := getStatus(); got != newStatus {
		t.Errorf("got %d, want %d", got, newStatus)
	}

	// GetLatestModuleVersions should return nil.
	got, err := testDB.GetLatestModuleVersions(t.Context(), modulePath)
	if err != nil {
		t.Fatal(err)
	}
	if got != nil {
		t.Errorf("got %v, want nil", got)
	}

	// A new failure status should overwrite.
	newStatus = 404
	if err := testDB.UpdateLatestModuleVersionsStatus(t.Context(), modulePath, newStatus); err != nil {
		t.Fatal(err)
	}
	if got := getStatus(); got != newStatus {
		t.Errorf("got %d, want %d", got, newStatus)
	}

	// Good information overwrites.
	lmv, err := internal.NewLatestModuleVersions(modulePath, "v1.2.3", "v1.2.3", "", []byte(`module example.com/m`))
	if err != nil {
		t.Fatal(err)
	}
	if _, err := testDB.UpdateLatestModuleVersions(t.Context(), lmv); err != nil {
		t.Fatal(err)
	}
	if got := getStatus(); got != 200 {
		t.Errorf("got %d, want %d", got, 200)
	}

	// Once we have good information, a bad status won't remove it.
	if err := testDB.UpdateLatestModuleVersionsStatus(t.Context(), modulePath, 500); err != nil {
		t.Fatal(err)
	}
	got, err = testDB.GetLatestModuleVersions(t.Context(), modulePath)
	if err != nil {
		t.Fatal(err)
	}
	if got == nil {
		t.Error("got nil, want non-nil")
	}
}

func TestLatestModuleVersionsGood(t *testing.T) {
	// Verify that the good latest version is updated properly.
	t.Parallel()
	testDB, release := acquire(t)
	defer release()

	const modulePath = "example.com/m"

	check := func(want string) {
		t.Helper()
		got, err := testDB.GetLatestModuleVersions(t.Context(), modulePath)
		if err != nil {
			t.Fatal(err)
		}
		if got.GoodVersion != want {
			t.Fatalf("got %q, want %q", got.GoodVersion, want)
		}
	}

	// Add two good versions.
	const v1 = "v1.1.0"
	testDB.MustInsertModule(t, sample.Module(modulePath, v1, "pkg"))
	check(v1)

	// Good version should be updated.
	const v2 = "v1.2.0"
	testDB.MustInsertModule(t, sample.Module(modulePath, v2, "pkg"))
	check(v2)

	// New latest-version info retracts v2 (and itself); good version should switch to v1.
	testDB.MustInsertModuleGoMod(t.Context(), t, sample.Module(modulePath, "v1.3.0", "pkg"), fmt.Sprintf(`
		module %s
		retract v1.3.0
		retract %s
	`, modulePath, v2))
	check(v1)
}

func TestGetPathVersionsPagination(t *testing.T) {
	t.Parallel()
	testDB, release := acquire(t)
	defer release()

	modulePath := "pagination.co/module"
	versions := []string{
		"v2.0.0+incompatible",
		"v1.0.0",
		"v1.2.0",
		"v1.1.0",
		"v1.1.0-20200330121822-37ff63d4418a",
		"v2.0.0",
		"v1.1.5",
	}
	for _, v := range versions {
		testDB.MustInsertModule(t, sample.Module(modulePath, v, "pkg"))
	}

	packagePath := "pagination.co/module/pkg"

	// Sort in memory DESC, with incompatibles last.
	sortedVersions := slices.Clone(versions)
	slices.SortFunc(sortedVersions, func(v1, v2 string) int {
		if version.IsIncompatible(v1) != version.IsIncompatible(v2) {
			if version.IsIncompatible(v1) {
				return 1
			}
			return -1
		}
		// semver.Canonical removes build information, and thus +incompatible.
		// So this works if both are incompatible, or both are compatible.
		return -semver.Compare(semver.Canonical(v1), semver.Canonical(v2))
	})
	pageSize := 2
	limit := pageSize + 1
	start := ""
	versionIndex := 0

	for {
		mods, nextStart, err := testDB.GetPathVersions(t.Context(), packagePath, start, limit, version.TypeRelease, version.TypePrerelease, version.TypePseudo)
		if err != nil {
			t.Fatal(err)
		}
		if len(mods) == 0 {
			if versionIndex < len(sortedVersions) {
				t.Errorf("stopped paginating early: got %d versions, want %d", versionIndex, len(sortedVersions))
			}
			break
		}

		consume := len(mods)
		hasLookahead := len(mods) == limit
		if hasLookahead {
			consume = pageSize
		}

		// Expected sub-slice
		end := min(versionIndex+consume, len(sortedVersions))
		wantSubSlice := sortedVersions[versionIndex:end]

		var gotSubSlice []string
		for i := range consume {
			gotSubSlice = append(gotSubSlice, mods[i].Version)
		}
		if diff := cmp.Diff(wantSubSlice, gotSubSlice); diff != "" {
			t.Errorf("page content mismatch at index %d (-want +got):\n%s", versionIndex, diff)
		}

		versionIndex += consume

		if !hasLookahead {
			if versionIndex < len(sortedVersions) {
				t.Errorf("stopped paginating early (no lookahead): got %d versions, want %d", versionIndex, len(sortedVersions))
			}
			break
		}
		start = nextStart
	}
}