package interpreter

import (
	"fmt"
	"go/format"
	"masonry/lang"
	"strings"

	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

// ServerInterpreter converts Masonry AST to a simple Go HTTP server
type ServerInterpreter struct {
	entities  map[string]*lang.Entity
	endpoints map[string]*lang.Endpoint
	server    *lang.Server
}

// NewServerInterpreter creates a new server interpreter
func NewServerInterpreter() *ServerInterpreter {
	return &ServerInterpreter{
		entities:  make(map[string]*lang.Entity),
		endpoints: make(map[string]*lang.Endpoint),
	}
}

// Interpret processes the AST and generates server code
func (si *ServerInterpreter) Interpret(ast lang.AST) (string, error) {
	// First pass: collect all definitions
	for _, def := range ast.Definitions {
		if def.Server != nil {
			si.server = def.Server
		}
		if def.Entity != nil {
			si.entities[def.Entity.Name] = def.Entity
		}
		if def.Endpoint != nil {
			key := fmt.Sprintf("%s_%s", def.Endpoint.Method, strings.ReplaceAll(def.Endpoint.Path, "/", "_"))
			si.endpoints[key] = def.Endpoint
		}
	}

	// Generate the server code
	rawCode, err := si.generateServer()
	if err != nil {
		return "", err
	}

	// Format the code to remove unused imports and fix formatting
	formattedCode, err := format.Source([]byte(rawCode))
	if err != nil {
		// If formatting fails, return the raw code with a warning comment
		return "// Warning: Code formatting failed, but code should still be functional\n" + rawCode, nil
	}

	return string(formattedCode), nil
}

// generateServer creates the complete server code
func (si *ServerInterpreter) generateServer() (string, error) {
	var code strings.Builder

	// Package and imports - only include what's actually used
	code.WriteString(`package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"sync"
	"time"
	"github.com/google/uuid"
	"github.com/gorilla/mux"
)

`)

	// Generate entity structs
	code.WriteString("// Entity definitions\n")
	for _, entity := range si.entities {
		code.WriteString(si.generateEntityStruct(entity))
		code.WriteString("\n")
	}

	// Generate in-memory database
	code.WriteString(si.generateInMemoryDB())

	// Generate handlers
	code.WriteString("// HTTP Handlers\n")
	for _, entity := range si.entities {
		code.WriteString(si.generateEntityHandlers(entity))
	}

	// Generate custom endpoint handlers
	for _, endpoint := range si.endpoints {
		if endpoint.Entity == nil {
			code.WriteString(si.generateCustomEndpointHandler(endpoint))
		}
	}

	// Generate main function
	code.WriteString(si.generateMainFunction())

	return code.String(), nil
}

// generateEntityStruct creates a Go struct for an entity
func (si *ServerInterpreter) generateEntityStruct(entity *lang.Entity) string {
	var code strings.Builder

	if entity.Description != nil {
		code.WriteString(fmt.Sprintf("// %s - %s\n", entity.Name, *entity.Description))
	}

	code.WriteString(fmt.Sprintf("type %s struct {\n", entity.Name))

	// Always add ID field
	code.WriteString("\tID       string    `json:\"id\"`\n")
	code.WriteString("\tCreatedAt time.Time `json:\"created_at\"`\n")
	code.WriteString("\tUpdatedAt time.Time `json:\"updated_at\"`\n")

	for _, field := range entity.Fields {
		goType := si.convertToGoType(field.Type)
		jsonTag := strings.ToLower(field.Name)

		if !field.Required {
			goType = "*" + goType
		}

		code.WriteString(fmt.Sprintf("\t%s %s `json:\"%s\"`\n",
			cases.Title(language.English).String(field.Name), goType, jsonTag))
	}

	code.WriteString("}\n")
	return code.String()
}

// convertToGoType maps Masonry types to Go types
func (si *ServerInterpreter) convertToGoType(masonryType string) string {
	switch masonryType {
	case "string", "text", "email", "url":
		return "string"
	case "int", "number":
		return "int"
	case "float":
		return "float64"
	case "boolean":
		return "bool"
	case "uuid":
		return "string"
	case "timestamp":
		return "time.Time"
	default:
		return "string" // default fallback
	}
}

// generateInMemoryDB creates the in-memory database structure
func (si *ServerInterpreter) generateInMemoryDB() string {
	var code strings.Builder

	code.WriteString("// In-memory database\n")
	code.WriteString("type InMemoryDB struct {\n")
	code.WriteString("\tmu sync.RWMutex\n")

	for entityName := range si.entities {
		code.WriteString(fmt.Sprintf("\t%s map[string]*%s\n",
			strings.ToLower(entityName)+"s", entityName))
	}

	code.WriteString("}\n\n")

	code.WriteString("var db = &InMemoryDB{\n")
	for entityName := range si.entities {
		code.WriteString(fmt.Sprintf("\t%s: make(map[string]*%s),\n",
			strings.ToLower(entityName)+"s", entityName))
	}
	code.WriteString("}\n\n")

	return code.String()
}

// generateEntityHandlers creates CRUD handlers for an entity
func (si *ServerInterpreter) generateEntityHandlers(entity *lang.Entity) string {
	var code strings.Builder
	entityName := entity.Name
	entityLower := strings.ToLower(entityName)
	entityPlural := entityLower + "s"

	// List handler
	code.WriteString(fmt.Sprintf(`func list%sHandler(w http.ResponseWriter, r *http.Request) {
	db.mu.RLock()
	defer db.mu.RUnlock()
	
	var items []*%s
	for _, item := range db.%s {
		items = append(items, item)
	}
	
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(items)
}

`, entityName, entityName, entityPlural))

	// Get by ID handler
	code.WriteString(fmt.Sprintf(`func get%sHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	id := vars["id"]
	
	db.mu.RLock()
	item, exists := db.%s[id]
	db.mu.RUnlock()
	
	if !exists {
		http.Error(w, "%s not found", http.StatusNotFound)
		return
	}
	
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(item)
}

`, entityName, entityPlural, entityName))

	// Create handler
	code.WriteString(fmt.Sprintf(`func create%sHandler(w http.ResponseWriter, r *http.Request) {
	var item %s
	if err := json.NewDecoder(r.Body).Decode(&item); err != nil {
		http.Error(w, "Invalid JSON", http.StatusBadRequest)
		return
	}
	
	item.ID = uuid.New().String()
	item.CreatedAt = time.Now()
	item.UpdatedAt = time.Now()
	
	db.mu.Lock()
	db.%s[item.ID] = &item
	db.mu.Unlock()
	
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	json.NewEncoder(w).Encode(item)
}

`, entityName, entityName, entityPlural))

	// Update handler
	code.WriteString(fmt.Sprintf(`func update%sHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	id := vars["id"]
	
	db.mu.Lock()
	defer db.mu.Unlock()
	
	existing, exists := db.%s[id]
	if !exists {
		http.Error(w, "%s not found", http.StatusNotFound)
		return
	}
	
	var updates %s
	if err := json.NewDecoder(r.Body).Decode(&updates); err != nil {
		http.Error(w, "Invalid JSON", http.StatusBadRequest)
		return
	}
	
	// Preserve ID and timestamps
	updates.ID = existing.ID
	updates.CreatedAt = existing.CreatedAt
	updates.UpdatedAt = time.Now()
	
	db.%s[id] = &updates
	
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(updates)
}

`, entityName, entityPlural, entityName, entityName, entityPlural))

	// Delete handler
	code.WriteString(fmt.Sprintf(`func delete%sHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	id := vars["id"]
	
	db.mu.Lock()
	defer db.mu.Unlock()
	
	if _, exists := db.%s[id]; !exists {
		http.Error(w, "%s not found", http.StatusNotFound)
		return
	}
	
	delete(db.%s, id)
	w.WriteHeader(http.StatusNoContent)
}

`, entityName, entityPlural, entityName, entityPlural))

	return code.String()
}

// generateCustomEndpointHandler creates handlers for custom endpoints
func (si *ServerInterpreter) generateCustomEndpointHandler(endpoint *lang.Endpoint) string {
	var code strings.Builder

	handlerName := fmt.Sprintf("%s%sHandler",
		strings.ToLower(endpoint.Method),
		strings.ReplaceAll(cases.Title(language.English).String(endpoint.Path), "/", ""))

	code.WriteString(fmt.Sprintf(`func %s(w http.ResponseWriter, r *http.Request) {
	// Custom endpoint: %s %s
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]string{
		"message": "Custom endpoint %s %s",
		"status": "success",
	})
}

`, handlerName, endpoint.Method, endpoint.Path, endpoint.Method, endpoint.Path))

	return code.String()
}

// generateMainFunction creates the main function with routing
func (si *ServerInterpreter) generateMainFunction() string {
	var code strings.Builder

	code.WriteString("func main() {\n")
	code.WriteString("\tr := mux.NewRouter()\n\n")

	// Add routes for each entity
	for entityName := range si.entities {
		entityLower := strings.ToLower(entityName)
		entityPlural := entityLower + "s"

		code.WriteString(fmt.Sprintf("\t// %s routes\n", entityName))
		code.WriteString(fmt.Sprintf("\tr.HandleFunc(\"/%s\", list%sHandler).Methods(\"GET\")\n",
			entityPlural, entityName))
		code.WriteString(fmt.Sprintf("\tr.HandleFunc(\"/%s/{id}\", get%sHandler).Methods(\"GET\")\n",
			entityPlural, entityName))
		code.WriteString(fmt.Sprintf("\tr.HandleFunc(\"/%s\", create%sHandler).Methods(\"POST\")\n",
			entityPlural, entityName))
		code.WriteString(fmt.Sprintf("\tr.HandleFunc(\"/%s/{id}\", update%sHandler).Methods(\"PUT\")\n",
			entityPlural, entityName))
		code.WriteString(fmt.Sprintf("\tr.HandleFunc(\"/%s/{id}\", delete%sHandler).Methods(\"DELETE\")\n",
			entityPlural, entityName))
		code.WriteString("\n")
	}

	// Add custom endpoint routes
	for _, endpoint := range si.endpoints {
		if endpoint.Entity == nil {
			handlerName := fmt.Sprintf("%s%sHandler",
				strings.ToLower(endpoint.Method),
				strings.ReplaceAll(cases.Title(language.English).String(endpoint.Path), "/", ""))
			code.WriteString(fmt.Sprintf("\tr.HandleFunc(\"%s\", %s).Methods(\"%s\")\n",
				endpoint.Path, handlerName, endpoint.Method))
		}
	}

	// Server configuration
	host := "localhost"
	port := 8080

	if si.server != nil {
		for _, setting := range si.server.Settings {
			if setting.Host != nil {
				host = *setting.Host
			}
			if setting.Port != nil {
				port = *setting.Port
			}
		}
	}

	code.WriteString(fmt.Sprintf("\n\taddr := \"%s:%d\"\n", host, port))
	code.WriteString("\tfmt.Printf(\"Server starting on %s\\n\", addr)\n")
	code.WriteString("\tlog.Fatal(http.ListenAndServe(addr, r))\n")
	code.WriteString("}\n")

	return code.String()
}