package engine

import (
	"errors"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"testing"
)

type discoveryLoadConfig struct {
	Service struct {
		Settings map[string]string `yaml:"settings"`
	} `yaml:"service"`
	Settings map[string]string `yaml:"settings"`
	Value    string            `yaml:"value"`
}

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

	root := t.TempDir()
	mainPath := writeImportFile(t, root, "app.yml", `configkit:
  imports: [{path: fragments/extra.yml}]
settings: {main: selected}
`)
	importPath := writeImportFile(t, root, "fragments/extra.yml", "settings: {imported: value}\n")
	search := SearchConfig("app", SearchDirectory(root))
	options := Options[discoveryLoadConfig]{
		Imports: true, Filesystem: &FilesystemContext{Root: root}, destination: Keys("service"),
	}
	searched, err := testLoad(search, options)
	if err != nil {
		t.Fatal(err)
	}
	explicit, err := testLoad(File(mainPath), options)
	if err != nil {
		t.Fatal(err)
	}
	assertEquivalentDiscoveryLoads(t, searched.Config, searched.Inspection, explicit.Config, explicit.Inspection,
		Keys("service", "settings", "main"), Keys("service", "settings", "imported"))

	sources := searched.Sources()
	if len(sources) != 2 || sources[0].Kind != SourceKindFile || sources[0].Path != canonicalTestPath(t, mainPath) || sources[1].Path != canonicalTestPath(t, importPath) {
		t.Fatalf("searched source evidence = %#v", sources)
	}
}

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

	root := t.TempDir()
	mainPath := writeImportFile(t, root, "main.yml", "settings: {main: value}\n")
	underlayPath := writeImportFile(t, root, "underlay/base.yml", `configkit:
  imports: [{path: extra.yml}]
settings: {underlay: value}
`)
	importPath := writeImportFile(t, root, "underlay/extra.yml", "settings: {imported: value}\n")
	mainSearch := SearchConfig("", SearchDirectory(root, DirectorySearchOptions{Filenames: []FilenameGroup{CustomFilenames("main.yml")}}))
	underlaySearch := SearchConfig("", SearchDirectory(filepath.Join(root, "underlay"), DirectorySearchOptions{Filenames: []FilenameGroup{CustomFilenames("base.yml")}}))
	load := func(main, underlay Source) (*Loaded[discoveryLoadConfig], error) {
		return LoadLayered(
			Input{Source: main, Imports: true}, testSecretBinding(),
			LayeredOptions[discoveryLoadConfig]{Underlays: []Underlay{{Inputs: []Input{{Source: underlay, Imports: true}}}}},
		)
	}
	searched, err := load(mainSearch, underlaySearch)
	if err != nil {
		t.Fatal(err)
	}
	explicit, err := load(File(mainPath), File(underlayPath))
	if err != nil {
		t.Fatal(err)
	}
	assertEquivalentDiscoveryLoads(t, searched.Config, searched.Inspection, explicit.Config, explicit.Inspection,
		Keys("settings", "main"), Keys("settings", "underlay"), Keys("settings", "imported"))

	sources := searched.Inspection.Sources()
	if len(sources) != 3 || sources[0].ID != "source-1" || sources[0].Layer != LayerBase || sources[1].ID != "source-2" || sources[1].Layer != LayerUnderlay || sources[2].Path != canonicalTestPath(t, importPath) || sources[2].UnderlayIndex != 1 {
		t.Fatalf("layered search source evidence = %#v", sources)
	}
}

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

	root := t.TempDir()
	missing := filepath.Join(root, "missing.yml")
	defaults := func() discoveryLoadConfig {
		return discoveryLoadConfig{Value: "default"}
	}
	options := Options[discoveryLoadConfig]{
		Definition: Definition[discoveryLoadConfig]{Defaults: defaults},
		Imports:    true, Filesystem: &FilesystemContext{Root: root},
	}
	searched, err := testLoad(SearchConfig("", Paths(missing)), options)
	if err != nil {
		t.Fatal(err)
	}
	explicit, err := testLoad(NoSource(), options)
	if err != nil {
		t.Fatal(err)
	}
	assertEquivalentDiscoveryLoads(t, searched.Config, searched.Inspection, explicit.Config, explicit.Inspection, Keys("value"))
	if len(searched.Sources()) != 0 {
		t.Fatalf("optional exhausted search created sources: %#v", searched.Sources())
	}
}

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

	t.Run("malformed YAML", func(t *testing.T) {
		first := writeImportFile(t, t.TempDir(), "first.yml", ": malformed\n")
		writeImportFile(t, filepath.Dir(first), "later.yml", "value: valid\n")
		loaded, err := testLoad[discoveryLoadConfig](SearchConfig("", Paths(first, filepath.Join(filepath.Dir(first), "later.yml"))), Options[discoveryLoadConfig]{})
		if loaded != nil || err == nil {
			t.Fatalf("malformed selected source = %#v, %v", loaded, err)
		}
	})

	t.Run("version check", func(t *testing.T) {
		root := t.TempDir()
		first := writeImportFile(t, root, "first.yml", "version: rejected\n")
		writeImportFile(t, root, "later.yml", "version: accepted\n")
		var checked []string
		loaded, err := testLoad[discoveryLoadConfig](SearchConfig("", Paths(first, filepath.Join(root, "later.yml"))), Options[discoveryLoadConfig]{
			SourceVersionMode: sourceVersionModeIfPresent,
			Definition: Definition[discoveryLoadConfig]{Version: &VersionRule{
				Path: Keys("version"),
				Check: func(version Version, _ *Validation) error {
					checked = append(checked, version.Text)
					if version.Text == "rejected" {
						return errors.New("version rejected")
					}
					return nil
				},
			}},
		})
		if loaded != nil || err == nil || !reflect.DeepEqual(checked, []string{"rejected"}) {
			t.Fatalf("version failure search = %#v, %v; checked %#v", loaded, err, checked)
		}
	})

	t.Run("decode", func(t *testing.T) {
		root := t.TempDir()
		first := writeImportFile(t, root, "first.yml", "value: not-an-integer\n")
		writeImportFile(t, root, "later.yml", "value: 3\n")
		type config struct {
			Value int `yaml:"value"`
		}
		loaded, err := testLoad[config](SearchConfig("", Paths(first, filepath.Join(root, "later.yml"))), Options[config]{})
		if loaded != nil || err == nil {
			t.Fatalf("decode failure search = %#v, %v", loaded, err)
		}
	})
}

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

	root := t.TempDir()
	first := writeImportFile(t, root, "first.yml", "value: selected\n")
	_, err := testLoad[discoveryLoadConfig](SearchConfig("", Searches(Paths(first), Paths(""))), Options[discoveryLoadConfig]{})
	var loadErr *LoadError
	if !errors.As(err, &loadErr) {
		t.Fatalf("invalid later search error = %v, want *LoadError", err)
	}
	if len(loadErr.Diagnostics()) == 0 || loadErr.Diagnostics()[0].Code != CodeOptionsInvalid {
		t.Fatalf("invalid later search component diagnostics = %#v", loadErr.Diagnostics())
	}

	malformed := writeImportFile(t, t.TempDir(), "main.yml", ": malformed\n")
	loaded, err := LoadLayered(
		Input{Source: SearchConfig("", Paths(malformed))}, testSecretBinding(),
		LayeredOptions[discoveryLoadConfig]{Underlays: []Underlay{{Inputs: []Input{{Source: SearchConfig("", Paths(""))}}}}},
	)
	if loaded != nil || !errors.As(err, &loadErr) {
		t.Fatalf("invalid later underlay search = %#v, %v", loaded, err)
	}
	for _, diagnostic := range loadErr.Diagnostics() {
		if diagnostic.Code != CodeOptionsInvalid {
			t.Fatalf("layered validation acquired main before rejecting underlay: %#v", loadErr.Diagnostics())
		}
	}
}

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

	root := t.TempDir()
	first := writeImportFile(t, root, "first.yml", "value: first\n")
	writeImportFile(t, root, "later.yml", "value: later\n")
	search := SearchConfig("", Paths(first, filepath.Join(root, "later.yml")))
	options := Options[discoveryLoadConfig]{Filesystem: &FilesystemContext{BaseDir: root, Root: root}}
	_, err := testLoad[discoveryLoadConfig](search, options)
	var loadErr *LoadError
	if !errors.As(err, &loadErr) {
		t.Fatalf("selected file with explicit base error = %v, want *LoadError", err)
	}
	if len(loadErr.Diagnostics()) == 0 || loadErr.Diagnostics()[0].Code != CodeOptionsInvalid {
		t.Fatalf("selected file context diagnostics = %#v", loadErr.Diagnostics())
	}
}

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

	root := t.TempDir()
	file := writeImportFile(t, root, "config.yml", "value: first\n")
	source := SearchConfig("", SearchDirectory(root, DirectorySearchOptions{Filenames: []FilenameGroup{CustomFilenames("config.yml")}}))
	load := func() string {
		loaded, err := testLoad[discoveryLoadConfig](source, Options[discoveryLoadConfig]{})
		if err != nil {
			t.Fatal(err)
		}
		return loaded.Config.Value
	}
	if value := load(); value != "first" {
		t.Fatalf("first search value = %q", value)
	}
	if err := os.WriteFile(file, []byte("value: second\n"), 0o600); err != nil {
		t.Fatal(err)
	}
	if value := load(); value != "second" {
		t.Fatalf("updated search value = %q", value)
	}
}

func TestSearchSourceObservesUserConfigEnvironmentChanges(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Setenv("APPDATA", filepath.Join(t.TempDir(), "first"))
	} else {
		t.Setenv("XDG_CONFIG_HOME", filepath.Join(t.TempDir(), "first"))
	}
	type config struct {
		Value string `yaml:"value"`
	}
	firstBase := os.Getenv("XDG_CONFIG_HOME")
	if runtime.GOOS == "windows" {
		firstBase = os.Getenv("APPDATA")
	}
	first := writeImportFile(t, firstBase, "app/app.yml", "value: first\n")
	secondBase := filepath.Join(t.TempDir(), "second")
	second := writeImportFile(t, secondBase, "app/app.yml", "value: second\n")
	source := SearchConfig("app", UserConfigDirectory())
	load := func() string {
		loaded, err := testLoad[config](source, Options[config]{})
		if err != nil {
			t.Fatal(err)
		}
		return loaded.Config.Value
	}
	if value := load(); value != "first" {
		t.Fatalf("first user-config search value = %q (%s)", value, first)
	}
	if runtime.GOOS == "windows" {
		t.Setenv("APPDATA", secondBase)
	} else {
		t.Setenv("XDG_CONFIG_HOME", secondBase)
	}
	if value := load(); value != "second" {
		t.Fatalf("updated user-config search value = %q (%s)", value, second)
	}

	// A reached dynamic base failure is terminal, but an earlier match must
	// prevent the invalid environment value from being resolved at all.
	direct := writeImportFile(t, t.TempDir(), "direct.yml", "value: direct\n")
	if runtime.GOOS == "windows" {
		t.Setenv("APPDATA", "relative")
	} else {
		t.Setenv("XDG_CONFIG_HOME", "relative")
	}
	early := SearchConfig("app", Searches(Paths(direct), UserConfigDirectory()))
	loaded, err := testLoad[config](early, Options[config]{})
	if err != nil || loaded.Config.Value != "direct" {
		t.Fatalf("early match with unavailable later base = %#v, %v", loaded, err)
	}
}

func TestSearchSourceObservesWorkingDirectoryChanges(t *testing.T) {
	original, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() {
		if err := os.Chdir(original); err != nil {
			t.Errorf("restore working directory: %v", err)
		}
	})
	firstDir := t.TempDir()
	secondDir := t.TempDir()
	writeImportFile(t, firstDir, "app.yml", "value: first\n")
	writeImportFile(t, secondDir, "app.yml", "value: second\n")
	source := SearchConfig("app", WorkingDirectory())
	load := func() string {
		loaded, err := testLoad[discoveryLoadConfig](source, Options[discoveryLoadConfig]{})
		if err != nil {
			t.Fatal(err)
		}
		return loaded.Config.Value
	}
	if err := os.Chdir(firstDir); err != nil {
		t.Fatal(err)
	}
	if value := load(); value != "first" {
		t.Fatalf("first working-directory search value = %q", value)
	}
	if err := os.Chdir(secondDir); err != nil {
		t.Fatal(err)
	}
	if value := load(); value != "second" {
		t.Fatalf("updated working-directory search value = %q", value)
	}
}

func assertEquivalentDiscoveryLoads[T any](t *testing.T, leftConfig T, left *Inspection, rightConfig T, right *Inspection, presencePaths ...Path) {
	t.Helper()
	if !reflect.DeepEqual(leftConfig, rightConfig) {
		t.Fatalf("search config %#v differs from explicit file config %#v", leftConfig, rightConfig)
	}
	leftSources, rightSources := left.Sources(), right.Sources()
	if !reflect.DeepEqual(leftSources, rightSources) {
		t.Fatalf("search sources %#v differ from explicit file sources %#v", leftSources, rightSources)
	}
	leftMetadata, rightMetadata := left.Metadata(), right.Metadata()
	for _, path := range presencePaths {
		leftInfo, leftPresent := leftMetadata.Lookup(path)
		rightInfo, rightPresent := rightMetadata.Lookup(path)
		if leftPresent != rightPresent || !reflect.DeepEqual(leftInfo, rightInfo) {
			t.Fatalf("search metadata at %s = %#v, %v; explicit metadata = %#v, %v", path.String(), leftInfo, leftPresent, rightInfo, rightPresent)
		}
	}
	for _, source := range leftSources {
		leftContext, leftOK := left.SourceContext(source.ID)
		rightContext, rightOK := right.SourceContext(source.ID)
		if leftOK != rightOK || leftContext.BaseDir != rightContext.BaseDir || (leftContext.FS != nil) != (rightContext.FS != nil) {
			t.Fatalf("search context for %s = %#v, %v; explicit context = %#v, %v", source.ID, leftContext, leftOK, rightContext, rightOK)
		}
	}
}