package build

import (
	"context"
	"fmt"
	"go/token"
	"os"
	"path/filepath"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"
)

// ArtifactResult is the outcome of a make:* command.
type ArtifactResult struct {
	PluginDir string
	Files     []string
	Hint      string
}

type artifactData struct {
	PluginID    string
	Ident       string
	Table       string
	Func        string
	Worker      string
	Kind        string
	ConfigDir   string
	PluginPath  string
	Snake       string
	MigrationID string
	UpSQL       string
	DownSQL     string
	CommandName string
	Description string
}

var migrationNow = func() time.Time { return time.Now().UTC() }

// MakeModel writes a GORM model and, unless noMigration is set, a create-table migration.
func MakeModel(ctx context.Context, startDir, pluginID, name string, noMigration bool) (ArtifactResult, error) {
	plugin, err := resolvePlugin(startDir, pluginID)
	if err != nil {
		return ArtifactResult{}, err
	}
	if err := validateExportedIdent(name); err != nil {
		return ArtifactResult{}, fmt.Errorf("build: model: %w", err)
	}
	table, err := modelTableName(plugin.ID, name)
	if err != nil {
		return ArtifactResult{}, err
	}
	modelRel := filepath.Join("models", toSnake(name)+".go")
	if err := rejectDuplicateFile(plugin.Dir, modelRel); err != nil {
		return ArtifactResult{}, err
	}
	if err := rejectDuplicateIdent(plugin.Dir, "models", name); err != nil {
		return ArtifactResult{}, err
	}

	data := artifactData{
		PluginID: plugin.ID,
		Ident:    name,
		Table:    table,
	}
	src, err := renderStub("model.go", data)
	if err != nil {
		return ArtifactResult{}, err
	}

	var created []string
	rollback := true
	defer func() {
		if rollback {
			for _, path := range created {
				os.Remove(path)
			}
		}
	}()

	modelPath := filepath.Join(plugin.Dir, modelRel)
	if err := writeFile(modelPath, src); err != nil {
		return ArtifactResult{}, err
	}
	created = append(created, modelPath)

	if !noMigration {
		migFunc := "Create" + exportedPlural(name)
		if err := rejectDuplicateIdent(plugin.Dir, "updates", migFunc); err != nil {
			return ArtifactResult{}, err
		}
		migID, migRel, err := nextMigrationFile(plugin.Dir, "create_"+table)
		if err != nil {
			return ArtifactResult{}, err
		}
		migSrc, err := renderStub("migration.go", artifactData{
			Func:        migFunc,
			MigrationID: migID,
			UpSQL:       createTableSQL(table),
			DownSQL:     "DROP TABLE IF EXISTS " + table,
		})
		if err != nil {
			return ArtifactResult{}, err
		}
		migPath := filepath.Join(plugin.Dir, migRel)
		if err := writeFile(migPath, migSrc); err != nil {
			return ArtifactResult{}, err
		}
		created = append(created, migPath)
	}

	if err := finishArtifact(ctx, plugin); err != nil {
		return ArtifactResult{}, err
	}
	rollback = false
	return ArtifactResult{PluginDir: plugin.Dir, Files: created, Hint: plugin.Hint}, nil
}

// MakeMigration writes an ordered gormigrate stub in updates/.
func MakeMigration(ctx context.Context, startDir, pluginID, name string) (ArtifactResult, error) {
	plugin, err := resolvePlugin(startDir, pluginID)
	if err != nil {
		return ArtifactResult{}, err
	}
	if err := validateExportedIdent(name); err != nil {
		return ArtifactResult{}, fmt.Errorf("build: migration: %w", err)
	}
	if err := rejectDuplicateIdent(plugin.Dir, "updates", name); err != nil {
		return ArtifactResult{}, err
	}
	slug := toSnake(name)
	migID, migRel, err := nextMigrationFile(plugin.Dir, slug)
	if err != nil {
		return ArtifactResult{}, err
	}
	src, err := renderStub("migration.go", artifactData{
		Func:        name,
		MigrationID: migID,
		UpSQL:       "SELECT 1",
		DownSQL:     "SELECT 1",
	})
	if err != nil {
		return ArtifactResult{}, err
	}

	path := filepath.Join(plugin.Dir, migRel)
	if err := writeFile(path, src); err != nil {
		return ArtifactResult{}, err
	}
	if err := finishArtifact(ctx, plugin); err != nil {
		os.Remove(path)
		return ArtifactResult{}, err
	}
	return ArtifactResult{PluginDir: plugin.Dir, Files: []string{path}, Hint: plugin.Hint}, nil
}

// MakeCommand writes a bonfire.Command stub in console/.
func MakeCommand(ctx context.Context, startDir, pluginID, name string) (ArtifactResult, error) {
	plugin, err := resolvePlugin(startDir, pluginID)
	if err != nil {
		return ArtifactResult{}, err
	}
	if err := validateExportedIdent(name); err != nil {
		return ArtifactResult{}, fmt.Errorf("build: command: %w", err)
	}
	fn := name + "Command"
	if err := rejectDuplicateIdent(plugin.Dir, "console", fn); err != nil {
		return ArtifactResult{}, err
	}
	rel := filepath.Join("console", toSnake(name)+".go")
	if err := rejectDuplicateFile(plugin.Dir, rel); err != nil {
		return ArtifactResult{}, err
	}
	cmdName := pluginName(plugin.ID) + ":" + toSnake(name)
	src, err := renderStub("command.go", artifactData{
		Func:        fn,
		CommandName: cmdName,
		Description: "TODO: describe " + cmdName,
	})
	if err != nil {
		return ArtifactResult{}, err
	}
	path := filepath.Join(plugin.Dir, rel)
	if err := writeFile(path, src); err != nil {
		return ArtifactResult{}, err
	}
	if err := finishArtifact(ctx, plugin); err != nil {
		os.Remove(path)
		return ArtifactResult{}, err
	}
	return ArtifactResult{PluginDir: plugin.Dir, Files: []string{path}, Hint: plugin.Hint}, nil
}

// MakeJob writes a pact.Job stub without importing River.
func MakeJob(ctx context.Context, startDir, pluginID, name string) (ArtifactResult, error) {
	plugin, err := resolvePlugin(startDir, pluginID)
	if err != nil {
		return ArtifactResult{}, err
	}
	if err := validateExportedIdent(name); err != nil {
		return ArtifactResult{}, fmt.Errorf("build: job: %w", err)
	}
	fn := name + "Job"
	if err := rejectDuplicateIdent(plugin.Dir, "jobs", fn); err != nil {
		return ArtifactResult{}, err
	}
	rel := filepath.Join("jobs", toSnake(name)+".go")
	if err := rejectDuplicateFile(plugin.Dir, rel); err != nil {
		return ArtifactResult{}, err
	}
	src, err := renderStub("job.go", artifactData{
		Ident:  name,
		Func:   fn,
		Worker: unexportedIdent(name) + "Job",
		Kind:   plugin.ID + "." + toSnake(name),
	})
	if err != nil {
		return ArtifactResult{}, err
	}
	path := filepath.Join(plugin.Dir, rel)
	if err := writeFile(path, src); err != nil {
		return ArtifactResult{}, err
	}
	if err := finishArtifact(ctx, plugin); err != nil {
		os.Remove(path)
		return ArtifactResult{}, err
	}
	return ArtifactResult{PluginDir: plugin.Dir, Files: []string{path}, Hint: plugin.Hint}, nil
}

// MakeAdminController writes a pact.AdminController and Winter-shaped YAML.
func MakeAdminController(ctx context.Context, startDir, pluginID, name string) (ArtifactResult, error) {
	plugin, err := resolvePlugin(startDir, pluginID)
	if err != nil {
		return ArtifactResult{}, err
	}
	if err := validateExportedIdent(name); err != nil {
		return ArtifactResult{}, fmt.Errorf("build: admin-controller: %w", err)
	}
	fn := name + "Controller"
	if err := rejectDuplicateIdent(plugin.Dir, "controllers", fn); err != nil {
		return ArtifactResult{}, err
	}
	snake := toSnake(name)
	rel := filepath.Join("controllers", snake+".go")
	if err := rejectDuplicateFile(plugin.Dir, rel); err != nil {
		return ArtifactResult{}, err
	}
	configDir := filepath.ToSlash(filepath.Join("controllers", snake))
	formRel := filepath.Join("controllers", snake, "config_form.yaml")
	listRel := filepath.Join("controllers", snake, "config_list.yaml")
	fieldsRel := filepath.Join("models", snake, "fields.yaml")
	columnsRel := filepath.Join("models", snake, "columns.yaml")
	for _, yamlRel := range []string{formRel, listRel, fieldsRel, columnsRel} {
		if err := rejectDuplicateFile(plugin.Dir, yamlRel); err != nil {
			return ArtifactResult{}, err
		}
	}
	data := artifactData{
		Ident:      name,
		Func:       fn,
		Worker:     unexportedIdent(name) + "Admin",
		Kind:       plugin.ID + "." + snake,
		ConfigDir:  configDir,
		PluginPath: strings.ReplaceAll(plugin.ID, ".", "/"),
		Snake:      snake,
	}
	src, err := renderStub("admin_controller.go", data)
	if err != nil {
		return ArtifactResult{}, err
	}
	formSrc, err := renderStub("config_form.yaml", data)
	if err != nil {
		return ArtifactResult{}, err
	}
	listSrc, err := renderStub("config_list.yaml", data)
	if err != nil {
		return ArtifactResult{}, err
	}
	fieldsSrc, err := renderStub("fields.yaml", nil)
	if err != nil {
		return ArtifactResult{}, err
	}
	columnsSrc, err := renderStub("columns.yaml", nil)
	if err != nil {
		return ArtifactResult{}, err
	}

	var created []string
	rollback := true
	defer func() {
		if rollback {
			for _, path := range created {
				os.Remove(path)
			}
		}
	}()
	goPath := filepath.Join(plugin.Dir, rel)
	if err := writeFile(goPath, src); err != nil {
		return ArtifactResult{}, err
	}
	created = append(created, goPath)
	for _, item := range []struct {
		rel  string
		body []byte
	}{
		{formRel, formSrc},
		{listRel, listSrc},
		{fieldsRel, fieldsSrc},
		{columnsRel, columnsSrc},
	} {
		path := filepath.Join(plugin.Dir, item.rel)
		if err := writeFile(path, item.body); err != nil {
			return ArtifactResult{}, err
		}
		created = append(created, path)
	}
	if err := finishArtifact(ctx, plugin); err != nil {
		return ArtifactResult{}, err
	}
	rollback = false
	return ArtifactResult{PluginDir: plugin.Dir, Files: created, Hint: plugin.Hint}, nil
}

func unexportedIdent(name string) string {
	r, size := utf8.DecodeRuneInString(name)
	return string(unicode.ToLower(r)) + name[size:]
}

type pluginRef struct {
	Dir  string
	ID   string
	Hint string
}

func resolvePlugin(startDir, id string) (pluginRef, error) {
	appDir, err := findAppDir(startDir)
	if err != nil {
		return pluginRef{}, err
	}
	if id == "" {
		id, err = inferPluginID(startDir, appDir)
		if err != nil {
			return pluginRef{}, err
		}
	}
	if err := ValidatePluginID(id); err != nil {
		return pluginRef{}, fmt.Errorf("build: %w", err)
	}
	pluginDir, err := locatePluginDir(appDir, id)
	if err != nil {
		return pluginRef{}, err
	}
	if !underRoot(appDir, pluginDir) {
		return pluginRef{}, fmt.Errorf("build: plugin directory %q is outside the app root", pluginDir)
	}
	got, err := pluginIDFromGo(filepath.Join(pluginDir, "plugin.go"))
	if err != nil {
		return pluginRef{}, err
	}
	if got != id {
		return pluginRef{}, fmt.Errorf("build: plugin %s has id %s", pluginDir, got)
	}
	modPath, err := readModulePath(filepath.Join(pluginDir, "go.mod"))
	if err != nil {
		return pluginRef{}, err
	}
	if err := validateModulePath(modPath); err != nil {
		return pluginRef{}, fmt.Errorf("build: plugin module: %w", err)
	}
	return pluginRef{
		Dir:  pluginDir,
		ID:   id,
		Hint: accessorHint(filepath.Join(pluginDir, "plugin.go")),
	}, nil
}

func inferPluginID(start, appDir string) (string, error) {
	dir, err := filepath.Abs(start)
	if err != nil {
		return "", fmt.Errorf("build: resolve plugin directory: %w", err)
	}
	for {
		candidate := filepath.Join(dir, "plugin.go")
		if st, err := os.Stat(candidate); err == nil && !st.IsDir() {
			if !underRoot(appDir, dir) {
				return "", fmt.Errorf("build: plugin.go at %s is outside the app root", dir)
			}
			return pluginIDFromGo(candidate)
		}
		if dir == appDir {
			break
		}
		parent := filepath.Dir(dir)
		if parent == dir {
			break
		}
		dir = parent
	}
	return "", fmt.Errorf("build: plugin id omitted and no plugin.go found from %s", start)
}

func locatePluginDir(appDir, id string) (string, error) {
	m, err := LoadManifest(filepath.Join(appDir, manifestName))
	if err != nil {
		return "", err
	}
	for _, p := range m.Plugins {
		if p.ID != id {
			continue
		}
		if dir := localModuleDir(appDir, p.Module); dir != "" {
			if st, err := os.Stat(dir); err == nil && st.IsDir() {
				return dir, nil
			}
		}
	}
	candidate := filepath.Join(appDir, "plugins", pluginName(id))
	if !underRoot(appDir, candidate) {
		return "", fmt.Errorf("build: plugin path %q escapes the app root", candidate)
	}
	st, err := os.Stat(candidate)
	if err != nil {
		if os.IsNotExist(err) {
			return "", fmt.Errorf("build: plugin %s not found", id)
		}
		return "", fmt.Errorf("build: stat %s: %w", candidate, err)
	}
	if !st.IsDir() {
		return "", fmt.Errorf("build: plugin %s not found", id)
	}
	return candidate, nil
}

func finishArtifact(ctx context.Context, plugin pluginRef) error {
	if err := refreshRegistry(plugin.Dir); err != nil {
		return err
	}
	if err := runGo(ctx, plugin.Dir, "mod", "tidy"); err != nil {
		return err
	}
	return ensureToolchain(filepath.Join(plugin.Dir, "go.mod"))
}

func accessorHint(pluginGoPath string) string {
	body, err := os.ReadFile(pluginGoPath)
	if err != nil {
		return ""
	}
	src := string(body)
	needed := []string{
		"generatedModels",
		"generatedMigrations",
		"generatedCommands",
		"generatedJobs",
		"generatedAdminControllers",
	}
	var missing []string
	for _, name := range needed {
		if !strings.Contains(src, name+"(") {
			missing = append(missing, name+"()")
		}
	}
	if len(missing) == 0 {
		return ""
	}
	return "note: add " + strings.Join(missing, ", ") + " to plugin.go capability methods; handwritten slices should append these accessors"
}

func validateExportedIdent(name string) error {
	if name == "" {
		return fmt.Errorf("name is empty")
	}
	if strings.ContainsAny(name, "/\\ \t\r\n\"'`$;&|*?<>()[]{}") {
		return fmt.Errorf("%q contains invalid characters", name)
	}
	if !token.IsIdentifier(name) {
		return fmt.Errorf("%q is not a valid Go identifier", name)
	}
	if !token.IsExported(name) {
		return fmt.Errorf("%q must be an exported identifier", name)
	}
	return nil
}

func rejectDuplicateFile(pluginDir, rel string) error {
	path := filepath.Join(pluginDir, rel)
	if !underRoot(pluginDir, path) {
		return fmt.Errorf("build: artifact path %q escapes the plugin directory", rel)
	}
	if _, err := os.Stat(path); err == nil {
		return fmt.Errorf("build: %s already exists", rel)
	} else if !os.IsNotExist(err) {
		return fmt.Errorf("build: stat %s: %w", path, err)
	}
	return nil
}

func rejectDuplicateIdent(pluginDir, pkg, ident string) error {
	refs, err := scanGeneratedIdents(filepath.Join(pluginDir, pkg), pkg, identKind(pkg))
	if err != nil {
		return err
	}
	for _, ref := range refs {
		if ref.Ident == ident {
			return fmt.Errorf("build: %s.%s already exists", pkg, ident)
		}
	}
	return nil
}

func identKind(pkg string) identScanKind {
	switch pkg {
	case "models":
		return scanStructs
	case "updates":
		return scanMigrationFuncs
	case "console":
		return scanCommandFuncs
	case "jobs":
		return scanJobFuncs
	case "controllers":
		return scanAdminFuncs
	default:
		return scanStructs
	}
}

func nextMigrationFile(pluginDir, slug string) (id, rel string, err error) {
	if err := validateTableName(slug); err != nil {
		return "", "", err
	}
	updates := filepath.Join(pluginDir, "updates")
	ts := migrationNow().Format("20060102150405")
	for i := 0; i < 60; i++ {
		id = fmt.Sprintf("%s_%s", ts, slug)
		rel = filepath.Join("updates", id+".go")
		path := filepath.Join(pluginDir, rel)
		if !underRoot(pluginDir, path) {
			return "", "", fmt.Errorf("build: artifact path %q escapes the plugin directory", rel)
		}
		_, err := os.Stat(path)
		if os.IsNotExist(err) {
			if err := os.MkdirAll(updates, 0o755); err != nil {
				return "", "", fmt.Errorf("build: mkdir %s: %w", updates, err)
			}
			return id, rel, nil
		}
		if err != nil {
			return "", "", fmt.Errorf("build: stat %s: %w", path, err)
		}
		next, parseErr := time.Parse("20060102150405", ts)
		if parseErr != nil {
			return "", "", fmt.Errorf("build: migration timestamp: %w", parseErr)
		}
		ts = next.Add(time.Second).Format("20060102150405")
	}
	return "", "", fmt.Errorf("build: could not allocate a unique migration id for %s", slug)
}

func modelTableName(pluginID, typeName string) (string, error) {
	table := strings.ReplaceAll(pluginID, ".", "_") + "_" + pluralSnake(typeName)
	if err := validateTableName(table); err != nil {
		return "", err
	}
	return table, nil
}

func validateTableName(name string) error {
	if name == "" {
		return fmt.Errorf("build: table name is empty")
	}
	for _, r := range name {
		if r == '_' || (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
			continue
		}
		return fmt.Errorf("build: table name %q contains invalid characters", name)
	}
	return nil
}

func createTableSQL(table string) string {
	return "CREATE TABLE " + table + " (\n" +
		"                id BIGSERIAL PRIMARY KEY,\n" +
		"                created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),\n" +
		"                updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()\n" +
		"            )"
}

func toSnake(ident string) string {
	var b strings.Builder
	prevUpper := false
	for i, r := range ident {
		upper := unicode.IsUpper(r)
		if upper && i > 0 && !prevUpper {
			b.WriteByte('_')
		}
		b.WriteRune(unicode.ToLower(r))
		prevUpper = upper
	}
	return b.String()
}

func pluralSnake(ident string) string {
	return pluralize(toSnake(ident))
}

func exportedPlural(ident string) string {
	return snakeToExported(pluralSnake(ident))
}

func pluralize(word string) string {
	switch {
	case word == "":
		return word
	case strings.HasSuffix(word, "s") || strings.HasSuffix(word, "x") || strings.HasSuffix(word, "z") ||
		strings.HasSuffix(word, "ch") || strings.HasSuffix(word, "sh"):
		return word + "es"
	case strings.HasSuffix(word, "y"):
		r, _ := utf8.DecodeLastRuneInString(strings.TrimSuffix(word, "y"))
		if r != utf8.RuneError && !isVowel(r) {
			return strings.TrimSuffix(word, "y") + "ies"
		}
		return word + "s"
	default:
		return word + "s"
	}
}

func isVowel(r rune) bool {
	switch unicode.ToLower(r) {
	case 'a', 'e', 'i', 'o', 'u':
		return true
	default:
		return false
	}
}

func snakeToExported(snake string) string {
	parts := strings.Split(snake, "_")
	var b strings.Builder
	for _, part := range parts {
		if part == "" {
			continue
		}
		r, size := utf8.DecodeRuneInString(part)
		b.WriteRune(unicode.ToUpper(r))
		b.WriteString(part[size:])
	}
	return b.String()
}