package engine

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

type importTestConfig struct {
	Settings struct {
		Root   string `yaml:"root"`
		First  string `yaml:"first"`
		Nested string `yaml:"nested"`
		Second string `yaml:"second"`
	} `yaml:"settings"`
	Version string            `yaml:"version"`
	Items   map[string]string `yaml:"items"`
}

func TestLoadFormerDirectiveKeyIsApplicationData(t *testing.T) {
	type config struct {
		Legacy struct {
			Imports []struct {
				Path string `yaml:"path"`
			} `yaml:"imports"`
		} `yaml:"_configkit"`
	}
	for _, imports := range []bool{false, true} {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", "_configkit:\n  imports:\n    - path: nonexistent.yml\n")
		result, err := testLoad[config](File(mainPath), Options[config]{Imports: imports})
		if err != nil {
			t.Fatalf("Imports=%v: %v", imports, err)
		}
		if len(result.Config.Legacy.Imports) != 1 || result.Config.Legacy.Imports[0].Path != "nonexistent.yml" || len(result.Sources()) != 1 {
			t.Fatalf("Imports=%v: former directive was not retained as application data: %#v", imports, result)
		}
	}
}

func TestLoadTraversesPathImportsDepthFirstAndComposesOrigins(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "main.yml", `configkit:
  imports:
    - path: first.yml
    - path: second.yml
settings:
  root: root
`)
	firstPath := writeImportFile(t, directory, "first.yml", `configkit:
  imports:
    - path: nested/third.yml
settings:
  first: first
`)
	thirdPath := writeImportFile(t, directory, "nested/third.yml", "settings:\n  nested: nested\n")
	secondPath := writeImportFile(t, directory, "second.yml", "settings:\n  second: second\n")

	result, err := testLoad[importTestConfig](File(mainPath), Options[importTestConfig]{Imports: true})
	if err != nil {
		t.Fatal(err)
	}
	if got := result.Config.Settings; got.Root != "root" || got.First != "first" || got.Nested != "nested" || got.Second != "second" {
		t.Fatalf("composed settings = %#v", got)
	}
	sources := result.Sources()
	wantPaths := []string{canonicalTestPath(t, mainPath), canonicalTestPath(t, firstPath), canonicalTestPath(t, thirdPath), canonicalTestPath(t, secondPath)}
	gotPaths := make([]string, len(sources))
	for index, source := range sources {
		gotPaths[index] = source.Path
		if source.ID != "source-"+strconv.Itoa(index+1) {
			t.Errorf("source %d ID = %q", index, source.ID)
		}
		if index > 0 && source.ImportedFrom == nil {
			t.Errorf("source %d has no import location", index)
		}
	}
	if !reflect.DeepEqual(gotPaths, wantPaths) {
		t.Fatalf("source paths = %#v, want depth-first %#v", gotPaths, wantPaths)
	}
	info, ok := result.Metadata().Lookup(Keys("settings"))
	if !ok || !info.Explicit || len(info.Origin.Locations) != 4 {
		t.Fatalf("settings metadata = %#v, %v", info, ok)
	}
}

func TestLoadImportsFromProfilesDirectoryAsBaseInput(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: profiles/shared.yml}]}\n")
	writeImportFile(t, directory, "profiles/shared.yml", "settings: {root: imported}\n")

	result, err := testLoad[importTestConfig](File(mainPath), Options[importTestConfig]{Imports: true})
	if err != nil || result.Config.Settings.Root != "imported" || len(result.Sources()) != 2 ||
		result.Sources()[1].Layer != LayerBase {
		t.Fatalf("profiles import = %#v, %v", result, err)
	}
}

func TestLoadRejectsImportConflictsAndFragmentVersions(t *testing.T) {
	t.Run("all duplicate claimants", func(t *testing.T) {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", `configkit:
  imports:
    - path: one.yml
    - path: two.yml
    - path: three.yml
`)
		for index, name := range []string{"one.yml", "two.yml", "three.yml"} {
			writeImportFile(t, directory, name, "settings:\n  root: "+string(rune('a'+index))+"\n")
		}
		loadError := requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeComposeConflict)
		diagnostic := loadError.Diagnostics()[0]
		if diagnostic.Path.String() != "/settings/root" || diagnostic.Primary == nil || len(diagnostic.Related) != 2 {
			t.Fatalf("conflict diagnostic = %#v", diagnostic)
		}
	})

	versionRule := &VersionRule{Path: Keys("settings", "version"), Check: func(Version, *Validation) error { return nil }}
	for _, test := range []struct {
		name     string
		fragment string
	}{
		{name: "exact integer", fragment: "settings:\n  version: 4\n"},
		{name: "ancestor scalar", fragment: "settings: blocked\n"},
	} {
		t.Run(test.name, func(t *testing.T) {
			directory := t.TempDir()
			mainPath := writeImportFile(t, directory, "main.yml", "configkit:\n  imports:\n    - path: fragment.yml\n")
			writeImportFile(t, directory, "fragment.yml", test.fragment)
			loadError := requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true, Definition: Definition[importTestConfig]{Version: versionRule}}, CodeImportVersion)
			diagnostic := loadError.Diagnostics()[0]
			if diagnostic.Path.String() != "/settings/version" || diagnostic.Primary == nil || diagnostic.Primary.SourceID != "source-2" {
				t.Fatalf("version placement diagnostic = %#v", diagnostic)
			}
		})
	}
}

func TestLoadImportDirectiveValidationAndTemporaryGlobGate(t *testing.T) {
	tests := []struct {
		name string
		body string
		code Code
	}{
		{name: "directive kind", body: "configkit: []\n", code: CodeImportInvalid},
		{name: "unknown directive field", body: "configkit: {unknown: true}\n", code: CodeImportInvalid},
		{name: "imports kind", body: "configkit: {imports: {}}\n", code: CodeImportInvalid},
		{name: "declaration kind", body: "configkit: {imports: [file.yml]}\n", code: CodeImportInvalid},
		{name: "missing target", body: "configkit: {imports: [{optional: true}]}\n", code: CodeImportInvalid},
		{name: "two targets", body: "configkit: {imports: [{path: a.yml, glob: '*.yml'}]}\n", code: CodeImportInvalid},
		{name: "unknown declaration field", body: "configkit: {imports: [{path: a.yml, extra: true}]}\n", code: CodeImportInvalid},
		{name: "optional kind", body: "configkit: {imports: [{path: a.yml, optional: 'yes'}]}\n", code: CodeImportInvalid},
		{name: "nested directive", body: "nested: {configkit: {}}\n", code: CodeImportInvalid},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			directory := t.TempDir()
			mainPath := writeImportFile(t, directory, "main.yml", test.body)
			requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, test.code)
		})
	}
}

func TestLoadImportMissingContainmentAndRegularFileRules(t *testing.T) {
	t.Run("optional missing", func(t *testing.T) {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", `configkit:
  imports:
    - path: missing.yml
      optional: true
settings: {root: retained}
`)
		result, err := testLoad[importTestConfig](File(mainPath), Options[importTestConfig]{Imports: true})
		if err != nil || result.Config.Settings.Root != "retained" || len(result.Sources()) != 1 {
			t.Fatalf("optional result = %#v, %v", result, err)
		}
	})

	tests := []struct {
		name  string
		path  string
		setup func(*testing.T, string)
		code  Code
	}{
		{name: "required missing", path: "missing.yml", code: CodeImportMissing},
		{name: "parent traversal", path: "../outside.yml", setup: func(t *testing.T, directory string) {
			writeImportFile(t, filepath.Dir(directory), "outside.yml", "settings: {root: outside}\n")
		}, code: CodeImportOutsideRoot},
		{name: "directory", path: "directory", setup: func(t *testing.T, directory string) {
			if err := os.Mkdir(filepath.Join(directory, "directory"), 0o755); err != nil {
				t.Fatal(err)
			}
		}, code: CodeSourceNotRegular},
		{name: "absolute", path: "/tmp/configkit.yml", code: CodeImportInvalid},
		{name: "network URL", path: "https://example.invalid/config.yml", code: CodeImportInvalid},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			directory := t.TempDir()
			if test.setup != nil {
				test.setup(t, directory)
			}
			mainPath := writeImportFile(t, directory, "main.yml", "configkit:\n  imports:\n    - path: \""+test.path+"\"\n")
			requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, test.code)
		})
	}
}

func TestLoadImportIdentityReportsCyclesAndRepeatedRoutes(t *testing.T) {
	t.Run("cycle", func(t *testing.T) {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", "configkit:\n  imports: [{path: a.yml}]\n")
		writeImportFile(t, directory, "a.yml", "configkit:\n  imports: [{path: b.yml}]\n")
		writeImportFile(t, directory, "b.yml", "configkit:\n  imports: [{path: main.yml}]\n")
		loadError := requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeImportCycle)
		diagnostic := loadError.Diagnostics()[0]
		if diagnostic.Primary == nil || len(diagnostic.Related) != 2 || !strings.Contains(diagnostic.Message, "main.yml") || !strings.Contains(diagnostic.Message, "a.yml") || !strings.Contains(diagnostic.Message, "b.yml") {
			t.Fatalf("cycle diagnostic = %#v", diagnostic)
		}
	})

	t.Run("diamond", func(t *testing.T) {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", "configkit:\n  imports: [{path: left.yml}, {path: right.yml}]\n")
		writeImportFile(t, directory, "left.yml", "configkit:\n  imports: [{path: shared.yml}]\n")
		writeImportFile(t, directory, "right.yml", "configkit:\n  imports: [{path: shared.yml}]\n")
		writeImportFile(t, directory, "shared.yml", "settings: {root: shared}\n")
		loadError := requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeImportRepeated)
		diagnostic := loadError.Diagnostics()[0]
		if diagnostic.Primary == nil || len(diagnostic.Related) < 3 {
			t.Fatalf("repeated-route diagnostic = %#v", diagnostic)
		}
	})

	t.Run("symlink aliases", func(t *testing.T) {
		if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
			t.Skip("initial filesystem contract covers Linux and macOS")
		}
		directory := t.TempDir()
		writeImportFile(t, directory, "target.yml", "settings: {root: target}\n")
		if err := os.Symlink("target.yml", filepath.Join(directory, "first-link.yml")); err != nil {
			t.Skipf("symlinks unavailable: %v", err)
		}
		if err := os.Symlink("target.yml", filepath.Join(directory, "second-link.yml")); err != nil {
			t.Skipf("symlinks unavailable: %v", err)
		}
		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: first-link.yml}, {path: second-link.yml}]}\n")
		requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeImportRepeated)
	})
}

func TestLoadImportsCanonicalSymlinksAndKeepsHardLinksDistinct(t *testing.T) {
	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
		t.Skip("initial filesystem contract covers Linux and macOS")
	}
	t.Run("contained absolute symlink", func(t *testing.T) {
		directory := t.TempDir()
		target := writeImportFile(t, directory, "target.yml", "settings: {first: linked}\n")
		if err := os.Symlink(target, filepath.Join(directory, "link.yml")); err != nil {
			t.Skipf("symlinks unavailable: %v", err)
		}
		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: link.yml}]}\n")
		result, err := testLoad[importTestConfig](File(mainPath), Options[importTestConfig]{Imports: true})
		if err != nil || result.Config.Settings.First != "linked" || result.Sources()[1].Path != canonicalTestPath(t, target) {
			t.Fatalf("symlink result = %#v, %v", result, err)
		}
	})

	t.Run("symlink escape", func(t *testing.T) {
		root := t.TempDir()
		outside := t.TempDir()
		target := writeImportFile(t, outside, "outside.yml", "settings: {root: outside}\n")
		if err := os.Symlink(target, filepath.Join(root, "escape.yml")); err != nil {
			t.Skipf("symlinks unavailable: %v", err)
		}
		mainPath := writeImportFile(t, root, "main.yml", "configkit: {imports: [{path: escape.yml}]}\n")
		requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeImportOutsideRoot)
	})

	t.Run("hard links are path identities", func(t *testing.T) {
		directory := t.TempDir()
		one := writeImportFile(t, directory, "one.yml", "settings: {first: one}\n")
		if err := os.Link(one, filepath.Join(directory, "two.yml")); err != nil {
			t.Skipf("hard links unavailable: %v", err)
		}
		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: one.yml}, {path: two.yml}]}\n")
		requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeComposeConflict)
	})

	t.Run("canonicalization failure", func(t *testing.T) {
		directory := t.TempDir()
		if err := os.Symlink("loop.yml", filepath.Join(directory, "loop.yml")); err != nil {
			t.Skipf("symlinks unavailable: %v", err)
		}
		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: loop.yml}]}\n")
		requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeImportInvalid)
	})
}

func TestLoadByteAndReaderImportsRequireExplicitFilesystemContext(t *testing.T) {
	directory := t.TempDir()
	writeImportFile(t, directory, "fragment.yml", "settings: {first: imported}\n")
	input := []byte("configkit: {imports: [{path: fragment.yml}]}\n")
	context := &FilesystemContext{BaseDir: directory, Root: directory}
	for _, test := range []struct {
		name   string
		source func() Source
	}{
		{name: "bytes URI label", source: func() Source { return Bytes("s3://bucket/main.yml", input) }},
		{name: "reader URI label", source: func() Source { return Reader("https://example.invalid/main.yml", strings.NewReader(string(input))) }},
	} {
		t.Run(test.name, func(t *testing.T) {
			result, err := testLoad[importTestConfig](test.source(), Options[importTestConfig]{Imports: true, Filesystem: context})
			if err != nil || result.Config.Settings.First != "imported" {
				t.Fatalf("explicit filesystem result = %#v, %v", result, err)
			}
		})
	}
	requireLoadCode(t, Bytes("memory.yml", input), Options[importTestConfig]{Imports: true}, CodeOptionsInvalid)
	requireLoadCode(t, Bytes("memory.yml", input), Options[importTestConfig]{Imports: true, Filesystem: &FilesystemContext{BaseDir: "relative", Root: directory}}, CodeOptionsInvalid)
	requireLoadCode(t, Bytes("memory.yml", input), Options[importTestConfig]{Imports: true, Filesystem: &FilesystemContext{BaseDir: directory, Root: t.TempDir()}}, CodeImportOutsideRoot)
}

func TestFileImportRootCanContainTheSelectedFileDirectory(t *testing.T) {
	root := t.TempDir()
	mainPath := writeImportFile(t, root, "configs/main.yml", "configkit: {imports: [{path: ../shared.yml}]}\n")
	writeImportFile(t, root, "shared.yml", "settings: {root: shared}\n")
	result, err := testLoad[importTestConfig](File(mainPath), Options[importTestConfig]{
		Imports: true, Filesystem: &FilesystemContext{Root: root},
	})
	if err != nil || result.Config.Settings.Root != "shared" {
		t.Fatalf("explicit-root result = %#v, %v", result, err)
	}
	requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true, Filesystem: &FilesystemContext{BaseDir: filepath.Dir(mainPath), Root: root}}, CodeOptionsInvalid)
}

func TestImportedParseAndDecodeDiagnosticsKeepTheirSource(t *testing.T) {
	t.Run("parse", func(t *testing.T) {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: broken.yml}]}\n")
		writeImportFile(t, directory, "broken.yml", "settings: [\n")
		loadError := requireAnyLoadError(t, File(mainPath), Options[importTestConfig]{Imports: true})
		diagnostics := loadError.Diagnostics()
		if diagnostics[0].Code != CodeYAMLInvalid || diagnostics[0].Primary == nil || diagnostics[0].Primary.SourceID != "source-2" || len(loadError.Sources()) != 2 {
			t.Fatalf("parse failure = diagnostics %#v, sources %#v", diagnostics, loadError.Sources())
		}
	})

	t.Run("decode", func(t *testing.T) {
		directory := t.TempDir()
		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: unknown.yml}]}\n")
		writeImportFile(t, directory, "unknown.yml", "unknown: value\n")
		loadError := requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeDecodeUnknownField)
		diagnostic := loadError.Diagnostics()[0]
		if diagnostic.Primary == nil || diagnostic.Primary.SourceID != "source-2" {
			t.Fatalf("decode diagnostic = %#v", diagnostic)
		}
	})
}

func TestOptionalImportDoesNotSuppressUnsafeOrUnreadableTargets(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "outside.yml", "configkit: {imports: [{path: ../missing.yml, optional: true}]}\n")
	requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeImportOutsideRoot)

	locked := writeImportFile(t, directory, "locked.yml", "settings: {root: locked}\n")
	if err := os.Chmod(locked, 0); err != nil {
		t.Skipf("cannot create unreadable fixture: %v", err)
	}
	defer func() { _ = os.Chmod(locked, 0o600) }()
	if file, err := os.Open(locked); err == nil {
		_ = file.Close()
		t.Skip("filesystem does not enforce the unreadable-file fixture")
	}
	mainPath = writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: locked.yml, optional: true}]}\n")
	requireLoadCode(t, File(mainPath), Options[importTestConfig]{Imports: true}, CodeSourcePermission)
}

func TestImportTraversalEnforcesPrivateBudgets(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: one.yml}, {path: two.yml}]}\n")
	writeImportFile(t, directory, "one.yml", "settings: {first: one}\n")
	writeImportFile(t, directory, "two.yml", "settings: {second: two}\n")
	main := parseImportMain(t, mainPath)
	for _, test := range []struct {
		name   string
		limits importLimits
	}{
		{name: "source count", limits: importLimits{depth: 8, sources: 2, bytes: maxTotalBytes, nodes: maxDocumentNodes}},
		{name: "aggregate bytes", limits: importLimits{depth: 8, sources: 8, bytes: main.bytes + 1, nodes: maxDocumentNodes}},
		{name: "aggregate nodes", limits: importLimits{depth: 8, sources: 8, bytes: maxTotalBytes, nodes: countInputNodes(main.document) + 1}},
	} {
		t.Run(test.name, func(t *testing.T) {
			_, _, diagnostics := loadImportedDocuments(File(mainPath), nil, main, nil, test.limits)
			if len(diagnostics) != 1 || diagnostics[0].Code != CodeImportLimitExceeded {
				t.Fatalf("budget diagnostics = %#v", diagnostics)
			}
		})
	}

	writeImportFile(t, directory, "one.yml", "configkit: {imports: [{path: nested.yml}]}\n")
	writeImportFile(t, directory, "nested.yml", "settings: {nested: nested}\n")
	main = parseImportMain(t, mainPath)
	_, _, diagnostics := loadImportedDocuments(File(mainPath), nil, main, nil, importLimits{depth: 1, sources: 8, bytes: maxTotalBytes, nodes: maxDocumentNodes})
	if len(diagnostics) != 1 || diagnostics[0].Code != CodeImportLimitExceeded {
		t.Fatalf("depth diagnostics = %#v", diagnostics)
	}
}

func TestImportTraversalAcceptsExactPrivateBudgets(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: imported.yml}]}\n")
	importedPath := writeImportFile(t, directory, "imported.yml", "settings: {first: imported}\n")
	main := parseImportMain(t, mainPath)
	imported := parseImportMain(t, importedPath)
	data, err := os.ReadFile(importedPath)
	if err != nil {
		t.Fatal(err)
	}
	limits := importLimits{
		depth:   1,
		sources: 2,
		bytes:   main.bytes + int64(len(data)),
		nodes:   countInputNodes(main.document) + countInputNodes(imported.document),
	}
	composed, sources, diagnostics := loadImportedDocuments(File(mainPath), nil, main, nil, limits)
	if len(diagnostics) != 0 || composed == nil || len(sources) != 2 {
		t.Fatalf("exact-limit composition = (%#v, %#v, %#v)", composed, sources, diagnostics)
	}
}

func writeImportFile(t *testing.T, root, relative, contents string) string {
	t.Helper()
	filename := filepath.Join(root, filepath.FromSlash(relative))
	if err := os.MkdirAll(filepath.Dir(filename), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filename, []byte(contents), 0o600); err != nil {
		t.Fatal(err)
	}
	return filename
}

func canonicalTestPath(t *testing.T, filename string) string {
	t.Helper()
	canonical, err := canonicalExistingPath(filename)
	if err != nil {
		t.Fatal(err)
	}
	return canonical
}

func requireLoadCode(t *testing.T, source Source, options Options[importTestConfig], code Code) *LoadError {
	t.Helper()
	loadError := requireAnyLoadError(t, source, options)
	diagnostics := loadError.Diagnostics()
	if len(diagnostics) == 0 || diagnostics[0].Code != code {
		t.Fatalf("diagnostics = %#v, want %s", diagnostics, code)
	}
	return loadError
}

func requireAnyLoadError(t *testing.T, source Source, options Options[importTestConfig]) *LoadError {
	t.Helper()
	result, err := testLoad[importTestConfig](source, options)
	if result != nil || err == nil {
		t.Fatalf("result, error = %#v, %v", result, err)
	}
	var loadError *LoadError
	if !errors.As(err, &loadError) {
		t.Fatalf("error type = %T", err)
	}
	return loadError
}

func parseImportMain(t *testing.T, filename string) parsedSource {
	t.Helper()
	parsed, diagnostics := parseSource(File(filename), "source-1", defaultParseLimits())
	if len(diagnostics) != 0 {
		t.Fatalf("parse diagnostics = %#v", diagnostics)
	}
	return parsed
}