package engine

import (
	"errors"
	"io/fs"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"testing"
)

func TestSearchDescriptionEmptyAndSlugRequirements(t *testing.T) {
	t.Parallel()

	if diagnostics := validateSearch(Search{}, ""); len(diagnostics) != 0 {
		t.Fatalf("zero search diagnostics = %#v", diagnostics)
	}
	if diagnostics := validateSearch(Searches(), ""); len(diagnostics) != 0 {
		t.Fatalf("empty concatenation diagnostics = %#v", diagnostics)
	}
	if diagnostics := validateSearch(Paths(), ""); len(diagnostics) != 0 {
		t.Fatalf("empty path list diagnostics = %#v", diagnostics)
	}
	if diagnostics := validateSearch(Paths("relative/config.yml"), ""); len(diagnostics) != 0 {
		t.Fatalf("literal path unexpectedly requires a slug: %#v", diagnostics)
	}
	generic := SearchDirectory("configs", DirectorySearchOptions{Filenames: []FilenameGroup{GenericFilenames()}})
	if diagnostics := validateSearch(generic, ""); len(diagnostics) != 0 {
		t.Fatalf("generic-only directory unexpectedly requires a slug: %#v", diagnostics)
	}
	if diagnostics := validateSearch(SearchDirectory("configs"), ""); len(diagnostics) == 0 || diagnostics[0].Code != CodeOptionsInvalid {
		t.Fatalf("default named directory accepted an empty slug: %#v", diagnostics)
	}
	if diagnostics := validateSearch(UnixSystemDirectories(), "myapp"); len(diagnostics) != 0 {
		t.Fatalf("valid preset slug diagnostics = %#v", diagnostics)
	}
}

func TestSearchDescriptionSnapshotsInputs(t *testing.T) {
	t.Parallel()

	paths := []string{"first.yml", "second.yml"}
	pathSearch := Paths(paths...)
	paths[0] = "changed.yml"

	customNames := []string{"one.yml", "two.yml"}
	group := CustomFilenames(customNames...)
	customNames[0] = "changed.yml"
	groups := []FilenameGroup{group}
	options := DirectorySearchOptions{Filenames: groups}
	directorySearch := SearchDirectory("configs", options)
	groups[0] = GenericFilenames()
	options.Filenames[0] = NamedFilenames()

	searches := []Search{pathSearch, directorySearch}
	combined := Searches(searches...)
	searches[0] = Search{}

	if got := combined.entries[0].path; got != "first.yml" {
		t.Fatalf("snapshotted path = %q", got)
	}
	gotNames := combined.entries[2].filenames[0].names
	if len(gotNames) != 2 || gotNames[0] != "one.yml" || gotNames[1] != "two.yml" {
		t.Fatalf("snapshotted custom names = %#v", gotNames)
	}
	if diagnostics := validateSearch(combined, ""); len(diagnostics) != 0 {
		t.Fatalf("snapshot description diagnostics = %#v", diagnostics)
	}
}

func TestDirectoryFilenameDefaultsAndExplicitEmpty(t *testing.T) {
	t.Parallel()

	omitted := SearchDirectory("configs")
	if len(omitted.entries) != 1 || len(omitted.entries[0].filenames) != 2 || omitted.entries[0].filenames[0].kind != filenameGroupNamed || omitted.entries[0].filenames[1].kind != filenameGroupGeneric {
		t.Fatalf("omitted groups = %#v", omitted.entries)
	}
	explicitNil := SearchDirectory("configs", DirectorySearchOptions{})
	if len(explicitNil.entries[0].filenames) != 2 {
		t.Fatalf("nil filename selection did not use defaults: %#v", explicitNil.entries[0].filenames)
	}
	explicitEmpty := SearchDirectory("configs", DirectorySearchOptions{Filenames: []FilenameGroup{}})
	if explicitEmpty.entries[0].filenames == nil || len(explicitEmpty.entries[0].filenames) != 0 {
		t.Fatalf("explicit empty selection lost its distinction: %#v", explicitEmpty.entries[0].filenames)
	}
	if len(validateSearch(explicitEmpty, "")) != 0 {
		t.Fatal("explicit empty filename selection should need no slug")
	}
}

func TestSearchDescriptionArityAndErrorConcatenation(t *testing.T) {
	t.Parallel()

	tooMany := SearchDirectory("configs", DirectorySearchOptions{}, DirectorySearchOptions{})
	if diagnostics := validateSearch(tooMany, "app"); len(diagnostics) == 0 {
		t.Fatal("multiple option values should be invalid")
	}
	invalid := Paths("")
	combined := Searches(Paths("good.yml"), invalid)
	if diagnostics := validateSearch(combined, ""); len(diagnostics) == 0 {
		t.Fatal("concatenation lost a constructor error")
	}
	if diagnostics := validateSearch(Paths("good.yml", ""), ""); len(diagnostics) == 0 {
		t.Fatal("later invalid path was hidden by an earlier component")
	}
}

func TestSearchDescriptionPreservesFilenameGroupOrder(t *testing.T) {
	t.Parallel()

	groups := []FilenameGroup{GenericFilenames(), NamedFilenames(), CustomFilenames("override.yml")}
	search := SearchDirectory("configs", DirectorySearchOptions{Filenames: groups})
	got := search.entries[0].filenames
	if len(got) != 3 || got[0].kind != filenameGroupGeneric || got[1].kind != filenameGroupNamed || got[2].names[0] != "override.yml" {
		t.Fatalf("filename group order = %#v", got)
	}
	if got := SearchDirectory("configs", DirectorySearchOptions{Filenames: []FilenameGroup{CustomFilenames()}}).entries[0].filenames[0].names; len(got) != 0 {
		t.Fatalf("empty custom group = %#v", got)
	}
}

func TestFilenameComponentValidation(t *testing.T) {
	t.Parallel()

	for _, value := range []string{"", ".", "..", "nested/name", "bad\x00name"} {
		if validFilenameComponent(value) {
			t.Errorf("validFilenameComponent(%q) = true", value)
		}
	}
	if runtime.GOOS == "windows" {
		for _, value := range []string{"CON", "nul.txt", "name.", "bad:name"} {
			if validFilenameComponent(value) {
				t.Errorf("Windows component %q unexpectedly accepted", value)
			}
		}
	} else {
		for _, value := range []string{"name with spaces", "naïve"} {
			if !validFilenameComponent(value) {
				t.Errorf("host-valid component %q rejected", value)
			}
		}
	}
	if diagnostics := validateSearch(SearchDirectory("configs", DirectorySearchOptions{Filenames: []FilenameGroup{CustomFilenames("bad/name")}}), ""); len(diagnostics) == 0 {
		t.Fatal("invalid custom filename was not retained for validation")
	}
	for _, value := range []string{"CON", "nul.txt", "COM¹.log", "LPT³.txt", "name.", "bad:name", "bad\x01name"} {
		if validWindowsFilenameComponent(value) {
			t.Errorf("Windows component %q unexpectedly accepted", value)
		}
	}
	for _, value := range []string{"name with spaces", "naïve"} {
		if !validWindowsFilenameComponent(value) {
			t.Errorf("valid Windows component %q rejected", value)
		}
	}
}

func TestSearchCandidatesPreserveDirectoryAndGroupOrder(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	helpers := discoveryDirectoryHelpers{workingDir: func() (string, error) { return root, nil }}
	search := Searches(
		Paths("first.yml"),
		SearchDirectory("settings", DirectorySearchOptions{Filenames: []FilenameGroup{
			GenericFilenames(), CustomFilenames("special.yml"),
		}}),
		Paths("last.yml"),
	)
	candidates := collectSearchCandidates(t, search, "app", helpers)
	want := []string{
		filepath.Join(root, "first.yml"),
		filepath.Join(root, "settings", "config.yml"),
		filepath.Join(root, "settings", "config.yaml"),
		filepath.Join(root, "settings", "main.yml"),
		filepath.Join(root, "settings", "main.yaml"),
		filepath.Join(root, "settings", "special.yml"),
		filepath.Join(root, "last.yml"),
	}
	assertCandidatePaths(t, candidates, want)

	reversed := SearchDirectory("settings", DirectorySearchOptions{Filenames: []FilenameGroup{NamedFilenames(), GenericFilenames()}})
	reversedCandidates := collectSearchCandidates(t, reversed, "app", helpers)
	assertCandidatePaths(t, reversedCandidates[:2], []string{
		filepath.Join(root, "settings", "app.yml"),
		filepath.Join(root, "settings", "app.yaml"),
	})
}

func TestSearchPresetCandidateLists(t *testing.T) {
	t.Parallel()

	helpers := discoveryDirectoryHelpers{
		userConfigDir: func() (string, error) { return "/controlled/config", nil },
		userHomeDir:   func() (string, error) { return "/controlled/home", nil },
		workingDir:    func() (string, error) { return "/controlled/work", nil },
		unixSupported: func() bool { return true },
	}

	unix := collectSearchCandidates(t, UnixSystemDirectories(), "app", helpers)
	if len(unix) != 14 {
		t.Fatalf("Unix preset candidate count = %d: %#v", len(unix), unix)
	}
	assertCandidatePaths(t, unix, []string{
		"/usr/local/etc/app/app.yml", "/usr/local/etc/app/app.yaml", "/usr/local/etc/app/config.yml", "/usr/local/etc/app/config.yaml", "/usr/local/etc/app/main.yml", "/usr/local/etc/app/main.yaml",
		"/etc/app/app.yml", "/etc/app/app.yaml", "/etc/app/config.yml", "/etc/app/config.yaml", "/etc/app/main.yml", "/etc/app/main.yaml",
		"/etc/app.yml", "/etc/app.yaml",
	})

	user := collectSearchCandidates(t, UserConfigDirectory(), "app", helpers)
	assertCandidatePaths(t, user, []string{
		"/controlled/config/app/app.yml", "/controlled/config/app/app.yaml", "/controlled/config/app/config.yml", "/controlled/config/app/config.yaml", "/controlled/config/app/main.yml", "/controlled/config/app/main.yaml",
		"/controlled/config/app.yml", "/controlled/config/app.yaml",
	})
	home := collectSearchCandidates(t, HomeDirectory(), "app", helpers)
	assertCandidatePaths(t, home, []string{
		"/controlled/home/.app/app.yml", "/controlled/home/.app/app.yaml", "/controlled/home/.app/config.yml", "/controlled/home/.app/config.yaml", "/controlled/home/.app/main.yml", "/controlled/home/.app/main.yaml",
		"/controlled/home/app.yml", "/controlled/home/app.yaml",
	})
	working := collectSearchCandidates(t, WorkingDirectory(), "app", helpers)
	assertCandidatePaths(t, working, []string{"/controlled/work/app.yml", "/controlled/work/app.yaml"})
}

func TestSearchCandidateExpansionIsLazyAndSkipsEmptyDirectories(t *testing.T) {
	t.Parallel()

	configCalls := 0
	helpers := discoveryDirectoryHelpers{
		userConfigDir: func() (string, error) {
			configCalls++
			return "/controlled/config", nil
		},
		workingDir:    func() (string, error) { return "/controlled/work", nil },
		unixSupported: func() bool { return true },
	}
	search := Searches(Paths("/selected.yml"), UserConfigDirectory())
	iterator, diagnostics := newSearchCandidateIterator(search, "app", helpers)
	if len(diagnostics) != 0 {
		t.Fatalf("iterator diagnostics = %#v", diagnostics)
	}
	if candidate, ok, err := iterator.next(); err != nil || !ok || candidate != "/selected.yml" {
		t.Fatalf("first candidate = %q, %v, %v", candidate, ok, err)
	}
	if configCalls != 0 {
		t.Fatalf("later user directory resolved before consumption: %d calls", configCalls)
	}

	emptyOnly := SearchDirectory("should-not-resolve", DirectorySearchOptions{Filenames: []FilenameGroup{}})
	emptyCandidates := collectSearchCandidates(t, emptyOnly, "", helpers)
	if len(emptyCandidates) != 0 || configCalls != 0 {
		t.Fatalf("empty directory candidates = %#v, helper calls = %d", emptyCandidates, configCalls)
	}
	continued := collectSearchCandidates(t, Searches(emptyOnly, Paths("later.yml")), "", helpers)
	assertCandidatePaths(t, continued, []string{filepath.Join("/controlled/work", "later.yml")})
	if configCalls != 0 {
		t.Fatalf("empty directory base was resolved: %d calls", configCalls)
	}
}

func TestSearchCandidateBaseFailuresAndPlatformApplicability(t *testing.T) {
	t.Parallel()

	baseFailure := errors.New("controlled base failure")
	helpers := discoveryDirectoryHelpers{
		userConfigDir: func() (string, error) { return "", baseFailure },
		workingDir:    func() (string, error) { return "/controlled/work", nil },
		unixSupported: func() bool { return false },
	}
	iterator, diagnostics := newSearchCandidateIterator(UserConfigDirectory(), "app", helpers)
	if len(diagnostics) != 0 {
		t.Fatalf("user preset validation = %#v", diagnostics)
	}
	if _, ok, err := iterator.next(); ok || !errors.Is(err, baseFailure) {
		t.Fatalf("unavailable user base = ok %v, err %v", ok, err)
	}

	iterator, diagnostics = newSearchCandidateIterator(UnixSystemDirectories(), "app", helpers)
	if len(diagnostics) != 0 {
		t.Fatalf("Unix preset validation = %#v", diagnostics)
	}
	if _, ok, err := iterator.next(); ok || !errors.Is(err, errUnixSystemPresetUnavailable) {
		t.Fatalf("unsupported Unix preset = ok %v, err %v", ok, err)
	}

	iterator, diagnostics = newSearchCandidateIterator(Searches(Paths("/earlier.yml"), UnixSystemDirectories()), "app", helpers)
	if len(diagnostics) != 0 {
		t.Fatalf("composed Unix preset validation = %#v", diagnostics)
	}
	if candidate, ok, err := iterator.next(); err != nil || !ok || candidate != "/earlier.yml" {
		t.Fatalf("earlier candidate = %q, %v, %v", candidate, ok, err)
	}
}

func TestRelativeAndShellLikeSearchPathsRemainLiteral(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	helpers := discoveryDirectoryHelpers{workingDir: func() (string, error) { return root, nil }}
	search := Searches(Paths("~/literal.yml", "$CONFIG/*.yaml"), SearchDirectory("./settings", DirectorySearchOptions{Filenames: []FilenameGroup{CustomFilenames("name with spaces.yml")}}))
	candidates := collectSearchCandidates(t, search, "", helpers)
	assertCandidatePaths(t, candidates, []string{
		filepath.Join(root, "~/literal.yml"),
		filepath.Join(root, "$CONFIG/*.yaml"),
		filepath.Join(root, "settings", "name with spaces.yml"),
	})
}

func collectSearchCandidates(t *testing.T, search Search, application string, helpers discoveryDirectoryHelpers) []string {
	t.Helper()
	iterator, diagnostics := newSearchCandidateIterator(search, application, helpers)
	if len(diagnostics) != 0 {
		t.Fatalf("search validation = %#v", diagnostics)
	}
	var candidates []string
	for {
		candidate, ok, err := iterator.next()
		if err != nil {
			t.Fatalf("expand candidate: %v", err)
		}
		if !ok {
			return candidates
		}
		candidates = append(candidates, candidate)
	}
}

func assertCandidatePaths(t *testing.T, got, want []string) {
	t.Helper()
	if len(got) != len(want) {
		t.Fatalf("candidate count = %d, want %d: %#v", len(got), len(want), got)
	}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("candidate %d = %q, want %q", i, got[i], want[i])
		}
	}
}

func TestResolveSearchSelectsFirstExistingCandidate(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	first := filepath.Join(root, "first.yml")
	second := filepath.Join(root, "second.yml")
	writeDiscoveryFile(t, first, "value: first\n")
	writeDiscoveryFile(t, second, "value: second\n")
	selected, diagnostics := resolveSearchSource(Source{}, ptrSearch(Paths(filepath.Join(root, "missing.yml"), first, second)), "", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || selected.kind != sourceFile || selected.path != first {
		t.Fatalf("selection = %#v, diagnostics %#v", selected, diagnostics)
	}
	read, diagnostics := readSource(selected, "source-1", defaultSourceLimits())
	if len(diagnostics) != 0 || string(read.data) != "value: first\n" || read.info.Path != canonicalTestPath(t, first) {
		t.Fatalf("selected source read = %#v, diagnostics %#v", read, diagnostics)
	}
}

func TestResolveSearchNamedExtensionsAndNonregularSelection(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	writeDiscoveryFile(t, filepath.Join(root, "app.yml"), "value: yml\n")
	writeDiscoveryFile(t, filepath.Join(root, "app.yaml"), "value: yaml\n")
	selected, diagnostics := resolveSearchSource(Source{}, ptrSearch(SearchDirectory(root)), "app", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || selected.path != filepath.Join(root, "app.yml") {
		t.Fatalf("named extension selection = %#v, %#v", selected, diagnostics)
	}

	directory := filepath.Join(root, "subdirectory")
	if err := os.Mkdir(directory, 0o700); err != nil {
		t.Fatal(err)
	}
	good := filepath.Join(root, "good.yml")
	writeDiscoveryFile(t, good, "value: later\n")
	selected, diagnostics = resolveSearchSource(Source{}, ptrSearch(Paths(directory, good)), "", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || selected.path != directory {
		t.Fatalf("directory candidate selection = %#v, %#v", selected, diagnostics)
	}
	_, diagnostics = readSource(selected, "source-1", defaultSourceLimits())
	if len(diagnostics) != 1 || diagnostics[0].Code != CodeSourceNotRegular {
		t.Fatalf("selected directory read diagnostics = %#v", diagnostics)
	}
}

func TestResolveSearchContainedSymlinkAndNoFallbackAfterReadFailure(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	target := filepath.Join(root, "actual.yml")
	link := filepath.Join(root, "linked.yml")
	writeDiscoveryFile(t, target, "value: linked\n")
	if err := os.Symlink(target, link); err != nil {
		t.Skipf("symlinks unavailable: %v", err)
	}
	writeDiscoveryFile(t, filepath.Join(root, "later.yml"), "value: later\n")
	selected, diagnostics := resolveSearchSource(Source{}, ptrSearch(Paths(link, filepath.Join(root, "later.yml"))), "", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || selected.path != link {
		t.Fatalf("symlink selection = %#v, %#v", selected, diagnostics)
	}
	read, diagnostics := readSource(selected, "source-1", defaultSourceLimits())
	if len(diagnostics) != 0 || string(read.data) != "value: linked\n" || read.info.Path != canonicalTestPath(t, target) {
		t.Fatalf("symlink read = %#v, %#v", read, diagnostics)
	}
	if err := os.Remove(target); err != nil {
		t.Fatal(err)
	}
	_, diagnostics = readSource(selected, "source-1", defaultSourceLimits())
	if len(diagnostics) != 1 || diagnostics[0].Code != CodeSourceMissing {
		t.Fatalf("selected source read failure = %#v", diagnostics)
	}
}

func TestResolveSearchRequiredAndOptionalExhaustion(t *testing.T) {
	t.Parallel()

	optional, diagnostics := resolveSearchSource(Source{}, ptrSearch(Search{}), "", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || optional.kind != sourceNone {
		t.Fatalf("optional empty search = %#v, %#v", optional, diagnostics)
	}
	_, diagnostics = resolveSearchSource(Source{}, ptrSearch(Search{}), "", true, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 1 || diagnostics[0].Code != CodeSourceMissing || diagnostics[0].Primary != nil || !strings.Contains(diagnostics[0].Message, "search") {
		t.Fatalf("required empty search = %#v", diagnostics)
	}

	root := t.TempDir()
	missing := filepath.Join(root, "missing.yml")
	optional, diagnostics = resolveSearchSource(Source{}, ptrSearch(Paths(missing)), "", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || optional.kind != sourceNone {
		t.Fatalf("optional missing search = %#v, %#v", optional, diagnostics)
	}
	_, diagnostics = resolveSearchSource(Source{}, ptrSearch(Paths(missing)), "", true, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 1 || diagnostics[0].Code != CodeSourceMissing {
		t.Fatalf("required missing search = %#v", diagnostics)
	}
}

func TestResolveSearchLeavesNonSearchSourcesUntouched(t *testing.T) {
	t.Parallel()

	source := Bytes("memory", []byte("value: unchanged\n"))
	resolved, diagnostics := resolveSearchSource(source, nil, "", false, discoveryDirectoryHelpers{}, discoveryHostProbe{})
	if len(diagnostics) != 0 || resolved.kind != sourceBytes || string(resolved.data) != "value: unchanged\n" {
		t.Fatalf("non-search source = %#v, diagnostics = %#v", resolved, diagnostics)
	}
}

func TestResolveSearchStopsOnReachedProbeError(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	first := filepath.Join(root, "first.yml")
	second := filepath.Join(root, "second.yml")
	writeDiscoveryFile(t, first, "value: first\n")
	writeDiscoveryFile(t, second, "value: second\n")
	statCalls := 0
	probe := discoveryHostProbe{stat: func(path string) (fs.FileInfo, error) {
		statCalls++
		return nil, fs.ErrPermission
	}}
	_, diagnostics := resolveSearchSource(Source{}, ptrSearch(Paths(first, second)), "", false, discoveryDirectoryHelpers{}, probe)
	if len(diagnostics) != 1 || diagnostics[0].Code != CodeSourcePermission || diagnostics[0].Primary != nil || statCalls != 1 {
		t.Fatalf("probe failure = %#v, stat calls = %d", diagnostics, statCalls)
	}
}

func TestResolveSearchLeavesLaterDirectoryUnresolvedAfterSelection(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	first := filepath.Join(root, "selected.yml")
	writeDiscoveryFile(t, first, "value: selected\n")
	baseCalls := 0
	helpers := discoveryDirectoryHelpers{userConfigDir: func() (string, error) {
		baseCalls++
		return "", errors.New("later base should not be reached")
	}}
	search := ptrSearch(Searches(Paths(first), UserConfigDirectory()))
	selected, diagnostics := resolveSearchSource(Source{}, search, "app", false, helpers, discoveryHostProbe{})
	if len(diagnostics) != 0 || selected.path != first || baseCalls != 0 {
		t.Fatalf("selected = %#v, diagnostics = %#v, later base calls = %d", selected, diagnostics, baseCalls)
	}
}

func TestResolveSearchTreatsShellLikeNamesLiterally(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	paths := []string{"~/literal.yml", "$CONFIG/literal.yml", "*.yaml"}
	for _, name := range paths {
		writeDiscoveryFile(t, filepath.Join(root, name), "value: literal\n")
	}
	helper := discoveryDirectoryHelpers{workingDir: func() (string, error) { return root, nil }}
	for _, name := range paths {
		selected, diagnostics := resolveSearchSource(Source{}, ptrSearch(Paths(name)), "", false, helper, discoveryHostProbe{})
		if len(diagnostics) != 0 || selected.path != filepath.Join(root, name) {
			t.Fatalf("literal %q selection = %#v, %#v", name, selected, diagnostics)
		}
	}
}

func ptrSearch(search Search) *Search { return &search }

func writeDiscoveryFile(t *testing.T, path, contents string) {
	t.Helper()
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(path, []byte(contents), 0o600); err != nil {
		t.Fatal(err)
	}
}