package interpreter

import (
	"bytes"
	"fmt"
	"masonry/lang"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"text/template"

	"golang.org/x/text/cases"
	"golang.org/x/text/language"
	"gopkg.in/yaml.v3"
)

// TemplateManifest defines the structure for multi-file template generation
type TemplateManifest struct {
	Name        string       `yaml:"name"`
	Description string       `yaml:"description"`
	Outputs     []OutputFile `yaml:"outputs"`
}

// OutputFile defines a single output file configuration
type OutputFile struct {
	Path        string `yaml:"path"`
	Template    string `yaml:"template"`
	Condition   string `yaml:"condition,omitempty"`
	Iterator    string `yaml:"iterator,omitempty"`
	ItemContext string `yaml:"item_context,omitempty"`
}

// TemplateInterpreter converts Masonry AST using template files
type TemplateInterpreter struct {
	registry *TemplateRegistry
}

// NewTemplateInterpreter creates a new template interpreter
func NewTemplateInterpreter() *TemplateInterpreter {
	return &TemplateInterpreter{
		registry: NewTemplateRegistry(),
	}
}

// InterpretFromFile parses a Masonry file and applies a template file
func (ti *TemplateInterpreter) InterpretFromFile(masonryFile, templateFile string) (string, error) {
	// Read the Masonry file
	masonryInput, err := os.ReadFile(masonryFile)
	if err != nil {
		return "", fmt.Errorf("error reading Masonry file: %w", err)
	}

	// Read the template file
	tmplText, err := os.ReadFile(templateFile)
	if err != nil {
		return "", fmt.Errorf("error reading template file: %w", err)
	}

	return ti.Interpret(string(masonryInput), string(tmplText))
}

// InterpretFromDirectory parses a Masonry file and applies templates from a directory
func (ti *TemplateInterpreter) InterpretFromDirectory(masonryFile, templateDir, rootTemplate string) (string, error) {
	// Load all templates from the directory
	err := ti.registry.LoadFromDirectory(templateDir)
	if err != nil {
		return "", fmt.Errorf("error loading templates from directory: %w", err)
	}

	// Read the Masonry file
	masonryInput, err := os.ReadFile(masonryFile)
	if err != nil {
		return "", fmt.Errorf("error reading Masonry file: %w", err)
	}

	// Get the root template content
	rootTemplatePath := filepath.Join(templateDir, rootTemplate)
	tmplText, err := os.ReadFile(rootTemplatePath)
	if err != nil {
		return "", fmt.Errorf("error reading root template file: %w", err)
	}

	return ti.Interpret(string(masonryInput), string(tmplText))
}

func (ti *TemplateInterpreter) Interpret(masonryInput string, tmplText string) (string, error) {
	ast, err := lang.ParseInput(masonryInput)
	if err != nil {
		return "", fmt.Errorf("error parsing Masonry input: %w", err)
	}

	// Create template using the unified FuncMap from the registry
	tmpl := template.Must(template.New("rootTemplate").Funcs(ti.registry.GetFuncMap()).Parse(tmplText))

	data := struct {
		AST      lang.AST
		Registry *TemplateRegistry
	}{
		AST:      ast,
		Registry: ti.registry,
	}

	var buf bytes.Buffer

	// Execute template
	err = tmpl.Execute(&buf, data)
	if err != nil {
		return "", fmt.Errorf("error executing template: %w", err)
	}

	return buf.String(), nil
}

// InterpretToFiles processes a manifest and returns multiple output files
func (ti *TemplateInterpreter) InterpretToFiles(masonryFile, templateDir, manifestFile string) (map[string]string, error) {
	// Load templates from directory
	err := ti.registry.LoadFromDirectory(templateDir)
	if err != nil {
		return nil, fmt.Errorf("error loading templates: %w", err)
	}

	// Load manifest
	manifestPath := filepath.Join(templateDir, manifestFile)
	manifestData, err := os.ReadFile(manifestPath)
	if err != nil {
		return nil, fmt.Errorf("error reading manifest: %w", err)
	}

	var manifest TemplateManifest
	err = yaml.Unmarshal(manifestData, &manifest)
	if err != nil {
		return nil, fmt.Errorf("error parsing manifest: %w", err)
	}

	// Parse Masonry input
	masonryInput, err := os.ReadFile(masonryFile)
	if err != nil {
		return nil, fmt.Errorf("error reading Masonry file: %w", err)
	}

	ast, err := lang.ParseInput(string(masonryInput))
	if err != nil {
		return nil, fmt.Errorf("error parsing Masonry input: %w", err)
	}

	// Process each output file
	outputs := make(map[string]string)
	for _, output := range manifest.Outputs {
		if output.Iterator != "" {
			// Handle per-item generation
			files, err := ti.generatePerItem(output, ast)
			if err != nil {
				return nil, err
			}
			for path, content := range files {
				outputs[path] = content
			}
		} else {
			// Handle single file generation (existing logic)
			if output.Condition != "" && !ti.evaluateCondition(output.Condition, ast) {
				continue
			}
			content, err := ti.executeTemplate(output.Template, ast)
			if err != nil {
				return nil, fmt.Errorf("error executing template %s: %w", output.Template, err)
			}

			// Execute path template to get dynamic filename
			pathContent, err := ti.executePathTemplate(output.Path, map[string]interface{}{
				"AST":      ast,
				"Registry": ti.registry,
			})
			if err != nil {
				return nil, fmt.Errorf("error executing path template: %w", err)
			}

			outputs[pathContent] = content
		}
	}

	return outputs, nil
}

// generatePerItem handles per-item iteration for multi-file generation
func (ti *TemplateInterpreter) generatePerItem(output OutputFile, ast lang.AST) (map[string]string, error) {
	items := ti.getIteratorItems(output.Iterator, ast)
	results := make(map[string]string)

	for _, item := range items {
		// Check condition with item context
		if output.Condition != "" && !ti.evaluateItemCondition(output.Condition, item, ast) {
			continue
		}

		// Create template data with item context
		data := ti.createItemTemplateData(output.ItemContext, item, ast)

		// Execute path template to get dynamic filename
		pathContent, err := ti.executePathTemplate(output.Path, data)
		if err != nil {
			return nil, err
		}

		// Execute content template
		content, err := ti.executeTemplateWithData(output.Template, data)
		if err != nil {
			return nil, err
		}

		results[pathContent] = content
	}

	return results, nil
}

// getIteratorItems extracts items from the AST based on the iterator type
func (ti *TemplateInterpreter) getIteratorItems(iterator string, ast lang.AST) []interface{} {
	var items []interface{}

	switch iterator {
	case "pages":
		for _, def := range ast.Definitions {
			if def.Page != nil {
				items = append(items, def.Page)
			}
		}
	case "entities":
		for _, def := range ast.Definitions {
			if def.Entity != nil {
				items = append(items, def.Entity)
			}
		}
	case "endpoints":
		for _, def := range ast.Definitions {
			if def.Endpoint != nil {
				items = append(items, def.Endpoint)
			}
		}
	case "servers":
		for _, def := range ast.Definitions {
			if def.Server != nil {
				items = append(items, def.Server)
			}
		}
	case "sections":
		items = ti.getAllSections(ast)
	case "components":
		items = ti.getAllComponents(ast)
	}

	return items
}

// getAllSections traverses the AST to collect all sections from all pages
func (ti *TemplateInterpreter) getAllSections(ast lang.AST) []interface{} {
	var sections []interface{}

	for _, def := range ast.Definitions {
		if def.Page != nil {
			// Get sections directly in the page
			for i := range def.Page.Sections {
				sections = append(sections, &def.Page.Sections[i])
			}
			// Recursively get nested sections
			sections = append(sections, ti.getSectionsFromSections(def.Page.Sections)...)
		}
	}

	return sections
}

// getSectionsFromSections recursively extracts sections from a list of sections
func (ti *TemplateInterpreter) getSectionsFromSections(sections []lang.Section) []interface{} {
	var result []interface{}

	for i := range sections {
		for j := range sections[i].Elements {
			element := &sections[i].Elements[j]
			if element.Section != nil {
				result = append(result, element.Section)
				// Recursively get sections from this section
				result = append(result, ti.getSectionsFromSections([]lang.Section{*element.Section})...)
			}
		}
	}

	return result
}

// getAllComponents traverses the AST to collect all components from pages, sections, and nested components
func (ti *TemplateInterpreter) getAllComponents(ast lang.AST) []interface{} {
	var components []interface{}

	for _, def := range ast.Definitions {
		if def.Page != nil {
			// Get components directly in the page
			for i := range def.Page.Components {
				components = append(components, &def.Page.Components[i])
			}
			// Get components from sections
			components = append(components, ti.getComponentsFromSections(def.Page.Sections)...)
		}
	}

	return components
}

// getComponentsFromSections recursively extracts components from sections
func (ti *TemplateInterpreter) getComponentsFromSections(sections []lang.Section) []interface{} {
	var components []interface{}

	for i := range sections {
		for j := range sections[i].Elements {
			element := &sections[i].Elements[j]
			if element.Component != nil {
				components = append(components, element.Component)
				// Get nested components from this component
				components = append(components, ti.getComponentsFromComponents([]lang.Component{*element.Component})...)
			} else if element.Section != nil {
				// Recursively get components from nested sections
				components = append(components, ti.getComponentsFromSections([]lang.Section{*element.Section})...)
			}
		}
	}

	return components
}

// getComponentsFromComponents recursively extracts components from nested components
func (ti *TemplateInterpreter) getComponentsFromComponents(components []lang.Component) []interface{} {
	var result []interface{}

	for i := range components {
		for j := range components[i].Elements {
			element := &components[i].Elements[j]
			if element.Section != nil {
				// Get components from nested sections
				result = append(result, ti.getComponentsFromSections([]lang.Section{*element.Section})...)
			}
		}
	}

	return result
}

// createItemTemplateData creates template data with the current item in context
func (ti *TemplateInterpreter) createItemTemplateData(itemContext string, item interface{}, ast lang.AST) map[string]interface{} {
	if itemContext == "" {
		itemContext = "Item" // default
	}

	return map[string]interface{}{
		"AST":       ast,
		"Registry":  ti.registry,
		itemContext: item,
	}
}

// evaluateCondition evaluates a condition string against the AST
func (ti *TemplateInterpreter) evaluateCondition(condition string, ast lang.AST) bool {
	switch condition {
	case "has_entities":
		for _, def := range ast.Definitions {
			if def.Entity != nil {
				return true
			}
		}
		return false
	case "has_endpoints":
		for _, def := range ast.Definitions {
			if def.Endpoint != nil {
				return true
			}
		}
		return false
	case "has_pages":
		for _, def := range ast.Definitions {
			if def.Page != nil {
				return true
			}
		}
		return false
	case "has_servers":
		for _, def := range ast.Definitions {
			if def.Server != nil {
				return true
			}
		}
		return false
	default:
		return true
	}
}

// evaluateItemCondition evaluates a condition for a specific item
func (ti *TemplateInterpreter) evaluateItemCondition(condition string, item interface{}, ast lang.AST) bool {
	_ = ast // Mark as intentionally unused for future extensibility
	switch condition {
	case "layout_admin":
		if page, ok := item.(*lang.Page); ok {
			return page.Layout == "admin"
		}
	case "layout_public":
		if page, ok := item.(*lang.Page); ok {
			return page.Layout == "public"
		}
	case "requires_auth":
		if page, ok := item.(*lang.Page); ok {
			return page.Auth
		}
		if endpoint, ok := item.(*lang.Endpoint); ok {
			return endpoint.Auth
		}
	}
	return true
}

// executeTemplate executes a template with the full AST context
func (ti *TemplateInterpreter) executeTemplate(templateName string, ast lang.AST) (string, error) {
	if tmpl, exists := ti.registry.templates[templateName]; exists {
		data := struct {
			AST      lang.AST
			Registry *TemplateRegistry
		}{
			AST:      ast,
			Registry: ti.registry,
		}

		var buf bytes.Buffer
		err := tmpl.Execute(&buf, data)
		return buf.String(), err
	}
	return "", fmt.Errorf("template %s not found", templateName)
}

// executeTemplateWithData executes a template with custom data
func (ti *TemplateInterpreter) executeTemplateWithData(templateName string, data interface{}) (string, error) {
	if tmpl, exists := ti.registry.templates[templateName]; exists {
		var buf bytes.Buffer
		err := tmpl.Execute(&buf, data)
		return buf.String(), err
	}
	return "", fmt.Errorf("template %s not found", templateName)
}

// executePathTemplate executes a path template to generate dynamic filenames
func (ti *TemplateInterpreter) executePathTemplate(pathTemplate string, data interface{}) (string, error) {
	tmpl, err := template.New("pathTemplate").Funcs(ti.registry.GetFuncMap()).Parse(pathTemplate)
	if err != nil {
		return "", fmt.Errorf("error parsing path template: %w", err)
	}

	var buf bytes.Buffer
	err = tmpl.Execute(&buf, data)
	if err != nil {
		return "", fmt.Errorf("error executing path template: %w", err)
	}

	return buf.String(), nil
}

type TemplateRegistry struct {
	templates map[string]*template.Template
	funcMap   template.FuncMap
}

func NewTemplateRegistry() *TemplateRegistry {
	tr := &TemplateRegistry{
		templates: make(map[string]*template.Template),
	}

	// Create funcMap with helper functions that will be available in all templates
	tr.funcMap = template.FuncMap{
		"executeTemplate": func(name string, data interface{}) (string, error) {
			if tmpl, exists := tr.templates[name]; exists {
				var buf strings.Builder
				err := tmpl.Execute(&buf, data)
				return buf.String(), err
			}
			return "", fmt.Errorf("template %s not found", name)
		},
		"hasTemplate": func(name string) bool {
			_, exists := tr.templates[name]
			return exists
		},
		"title": cases.Title(language.English).String,
		"lower": strings.ToLower,
		"upper": strings.ToUpper,
		"goType": func(t string) string {
			typeMap := map[string]string{
				"string":    "string",
				"int":       "int",
				"uuid":      "string",
				"boolean":   "bool",
				"timestamp": "time.Time",
				"text":      "string",
				"object":    "interface{}",
			}
			if goType, ok := typeMap[t]; ok {
				return goType
			}
			return "interface{}"
		},
		"pathToHandlerName": func(path string) string {
			// Convert "/users/{id}" to "Users"
			re := regexp.MustCompile(`[^a-zA-Z0-9]+`)
			name := re.ReplaceAllString(path, " ")
			name = strings.TrimSpace(name)
			name = cases.Title(language.English).String(name)
			return strings.ReplaceAll(name, " ", "")
		},
		"getHost": func(settings []lang.ServerSetting) string {
			for _, s := range settings {
				if s.Host != nil {
					if s.Host.Literal != nil {
						return "\"" + *s.Host.Literal + "\""
					}
					return fmt.Sprintf(`func() string { if v := os.Getenv("%s"); v != "" { return v }; return "%s" }()`, s.Host.EnvVar.Name, func() string {
						if s.Host.EnvVar.Default != nil {
							return *s.Host.EnvVar.Default
						}
						return "localhost"
					}())
				}
			}
			return "localhost"
		},
		"getPort": func(settings []lang.ServerSetting) string {
			for _, s := range settings {
				if s.Port != nil {
					if s.Port.Literal != nil {
						return strconv.Itoa(*s.Port.Literal)
					}
					return fmt.Sprintf(`func() string { if v := os.Getenv("%s"); v != "" { return v }; return "%s" }()`, s.Port.EnvVar.Name, func() string {
						if s.Port.EnvVar.Default != nil {
							return *s.Port.EnvVar.Default
						}
						return "8080"
					}())
				}
			}
			return "8080"
		},
		"getServerHostPort": func(settings []lang.ServerSetting) string {
			host := "localhost"
			port := 8080
			for _, s := range settings {
				if s.Host != nil {
					if s.Host.Literal != nil {
						host = *s.Host.Literal
					}
					if s.Host.EnvVar != nil && s.Host.EnvVar.Default != nil {
						host = *s.Host.EnvVar.Default
					}
					// If it's an env var, keep the default
				}
				if s.Port != nil {
					if s.Port.Literal != nil {
						port = *s.Port.Literal
					}
					if s.Port.EnvVar != nil && s.Port.EnvVar.Default != nil {
						if p, err := strconv.Atoi(*s.Port.EnvVar.Default); err == nil {
							port = p
						}
					}
					// If it's an env var, keep the default
				}
			}
			return fmt.Sprintf("%s:%d", host, port)
		},
		"slice": func() []interface{} {
			return []interface{}{}
		},
		"append": func(slice []interface{}, item interface{}) []interface{} {
			return append(slice, item)
		},
		"add": func(a, b int) int {
			return a + b
		},
		"derefString": func(s *string) string {
			if s != nil {
				return *s
			}
			return ""
		},
		"derefInt": func(i *int) int {
			if i != nil {
				return *i
			}
			return 0
		},
		"relativePrefix": func(path string) string {
			// Remove leading slash and split by "/"
			cleanPath := strings.TrimPrefix(path, "/")
			if cleanPath == "" {
				return "../"
			}

			parts := strings.Split(cleanPath, "/")
			depth := len(parts)

			// Build relative prefix with "../" for each level
			var prefix strings.Builder
			for i := 0; i < depth; i++ {
				prefix.WriteString("../")
			}

			return prefix.String()
		},
	}
	return tr
}

func (tr *TemplateRegistry) GetFuncMap() template.FuncMap {
	// Add the registry function to the existing funcMap
	funcMap := make(template.FuncMap)
	for k, v := range tr.funcMap {
		funcMap[k] = v
	}
	funcMap["registry"] = func() *TemplateRegistry { return tr }
	return funcMap
}

func (tr *TemplateRegistry) Register(name, content string) error {
	tmpl, err := template.New(name).Funcs(tr.funcMap).Parse(content)
	if err != nil {
		return err
	}
	tr.templates[name] = tmpl
	return nil
}

func (tr *TemplateRegistry) LoadFromDirectory(dir string) error {
	return filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if strings.HasSuffix(path, ".tmpl") {
			content, err := os.ReadFile(path)
			if err != nil {
				return err
			}
			name := strings.TrimSuffix(filepath.Base(path), ".tmpl")
			return tr.Register(name, string(content))
		}
		return nil
	})
}