package service

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"text/template"
	"time"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// CaptainCustomToolService implements business logic for CaptainCustomTool operations.
// Reference: Chatwoot enterprise/app/controllers/api/v1/captain/custom_tools_controller.rb
type CaptainCustomToolService struct {
	toolRepo *repository.CaptainCustomToolRepo
}

// NewCaptainCustomToolService creates a new CaptainCustomToolService.
func NewCaptainCustomToolService(toolRepo *repository.CaptainCustomToolRepo) *CaptainCustomToolService {
	return &CaptainCustomToolService{toolRepo: toolRepo}
}

// --- Request DTOs ---

// CreateCustomToolRequest is the DTO for creating a custom tool.
type CreateCustomToolRequest struct {
	Title            string          `json:"title" validate:"required"`
	Slug             string          `json:"slug" validate:"required"`
	Description      string          `json:"description"`
	EndpointURL      string          `json:"endpoint_url" validate:"required"`
	HTTPMethod       string          `json:"http_method"`
	AuthType         string          `json:"auth_type"`
	AuthConfig       json.RawMessage `json:"auth_config"`
	ParamSchema      json.RawMessage `json:"param_schema"`
	RequestTemplate  string          `json:"request_template"`
	ResponseTemplate string          `json:"response_template"`
}

// UpdateCustomToolRequest is the DTO for updating a custom tool.
type UpdateCustomToolRequest struct {
	Title            string          `json:"title"`
	Description      string          `json:"description"`
	EndpointURL      string          `json:"endpoint_url"`
	HTTPMethod       string          `json:"http_method"`
	AuthType         string          `json:"auth_type"`
	AuthConfig       json.RawMessage `json:"auth_config"`
	ParamSchema      json.RawMessage `json:"param_schema"`
	RequestTemplate  string          `json:"request_template"`
	ResponseTemplate string          `json:"response_template"`
	Enabled          *bool           `json:"enabled"`
}

// --- CRUD Operations ---

// Create creates a new CaptainCustomTool.
func (s *CaptainCustomToolService) Create(ctx context.Context, accountID uint, req *CreateCustomToolRequest) (*model.CaptainCustomTool, error) {
	// Default values
	httpMethod := req.HTTPMethod
	if httpMethod == "" {
		httpMethod = "GET"
	}
	authType := req.AuthType
	if authType == "" {
		authType = "none"
	}

	tool := &model.CaptainCustomTool{
		AccountID:        accountID,
		Title:            req.Title,
		Slug:             req.Slug,
		Description:      req.Description,
		EndpointURL:      req.EndpointURL,
		HTTPMethod:       httpMethod,
		AuthType:         model.ToolAuthType(authType),
		AuthConfig:       req.AuthConfig,
		ParamSchema:      req.ParamSchema,
		RequestTemplate:  req.RequestTemplate,
		ResponseTemplate: req.ResponseTemplate,
		Enabled:          true,
	}

	if err := s.toolRepo.Create(ctx, tool); err != nil {
		applogger.L().Errorf("Create captain custom tool: %v", err)
		return nil, fmt.Errorf("create custom tool: %w", err)
	}
	return tool, nil
}

// Get retrieves a custom tool by ID.
func (s *CaptainCustomToolService) Get(ctx context.Context, id uint) (*model.CaptainCustomTool, error) {
	tool, err := s.toolRepo.GetByID(ctx, id)
	if err != nil {
		applogger.L().Errorf("Get captain custom tool: %v", err)
		return nil, fmt.Errorf("get custom tool: %w", err)
	}
	return tool, nil
}

// Update updates an existing custom tool.
func (s *CaptainCustomToolService) Update(ctx context.Context, id uint, req *UpdateCustomToolRequest) (*model.CaptainCustomTool, error) {
	tool, err := s.toolRepo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("custom tool not found: %w", err)
	}

	if req.Title != "" {
		tool.Title = req.Title
	}
	if req.Description != "" {
		tool.Description = req.Description
	}
	if req.EndpointURL != "" {
		tool.EndpointURL = req.EndpointURL
	}
	if req.HTTPMethod != "" {
		tool.HTTPMethod = req.HTTPMethod
	}
	if req.AuthType != "" {
		tool.AuthType = model.ToolAuthType(req.AuthType)
	}
	if len(req.AuthConfig) > 0 && string(req.AuthConfig) != "null" {
		tool.AuthConfig = req.AuthConfig
	}
	if len(req.ParamSchema) > 0 && string(req.ParamSchema) != "null" {
		tool.ParamSchema = req.ParamSchema
	}
	if req.RequestTemplate != "" {
		tool.RequestTemplate = req.RequestTemplate
	}
	if req.ResponseTemplate != "" {
		tool.ResponseTemplate = req.ResponseTemplate
	}
	if req.Enabled != nil {
		tool.Enabled = *req.Enabled
	}

	if err := s.toolRepo.Update(ctx, tool); err != nil {
		applogger.L().Errorf("Update captain custom tool: %v", err)
		return nil, fmt.Errorf("update custom tool: %w", err)
	}
	return tool, nil
}

// Delete deletes a custom tool by ID.
func (s *CaptainCustomToolService) Delete(ctx context.Context, id uint) error {
	if err := s.toolRepo.Delete(ctx, id); err != nil {
		applogger.L().Errorf("Delete captain custom tool: %v", err)
		return fmt.Errorf("delete custom tool: %w", err)
	}
	return nil
}

// List retrieves custom tools for an account with pagination.
func (s *CaptainCustomToolService) List(ctx context.Context, accountID uint, offset, limit int) ([]model.CaptainCustomTool, int64, error) {
	tools, count, err := s.toolRepo.ListByAccount(ctx, accountID, offset, limit)
	if err != nil {
		applogger.L().Errorf("List captain custom tools: %v", err)
		return nil, 0, fmt.Errorf("list custom tools: %w", err)
	}
	return tools, count, nil
}

// --- Tool Execution ---

// ExecuteToolResult holds the result of executing a custom tool.
type ExecuteToolResult struct {
	Success bool        `json:"success"`
	Data    interface{} `json:"data"`
	Error   string      `json:"error,omitempty"`
}

// ExecuteTool calls the external HTTP endpoint configured in the custom tool.
// Reference: Chatwoot Captain::CustomTool#execute
func (s *CaptainCustomToolService) ExecuteTool(ctx context.Context, id uint, params map[string]interface{}) (*ExecuteToolResult, error) {
	tool, err := s.toolRepo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("custom tool not found: %w", err)
	}

	if !tool.Enabled {
		return nil, fmt.Errorf("custom tool is disabled")
	}

	// Build request body from template + params
	requestBody, err := buildRequestBody(tool.RequestTemplate, params)
	if err != nil {
		return nil, fmt.Errorf("build request body: %w", err)
	}

	// Create HTTP request
	method := strings.ToUpper(tool.HTTPMethod)
	var httpReq *http.Request
	if method == "GET" || method == "DELETE" {
		httpReq, err = http.NewRequestWithContext(ctx, method, tool.EndpointURL, nil)
	} else {
		httpReq, err = http.NewRequestWithContext(ctx, method, tool.EndpointURL, bytes.NewReader(requestBody))
	}
	if err != nil {
		return nil, fmt.Errorf("create HTTP request: %w", err)
	}

	// Set content type for methods with body
	if method != "GET" && method != "DELETE" {
		httpReq.Header.Set("Content-Type", "application/json")
	}

	// Apply authentication
	if err := applyAuth(httpReq, tool); err != nil {
		return nil, fmt.Errorf("apply auth: %w", err)
	}

	// Execute HTTP call
	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(httpReq)
	if err != nil {
		applogger.L().Errorf("ExecuteTool HTTP call: %v", err)
		return &ExecuteToolResult{Success: false, Error: err.Error()}, nil
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return nil, fmt.Errorf("read response: %w", err)
	}

	// Parse response through response template if defined
	var resultData interface{}
	if tool.ResponseTemplate != "" {
		parsed, err := parseResponseTemplate(tool.ResponseTemplate, respBody)
		if err != nil {
			applogger.L().Errorf("ExecuteTool parse response template: %v", err)
			resultData = string(respBody)
		} else {
			resultData = parsed
		}
	} else {
		// Try to parse as JSON; fall back to raw string
		var jsonData interface{}
		if err := json.Unmarshal(respBody, &jsonData); err == nil {
			resultData = jsonData
		} else {
			resultData = string(respBody)
		}
	}

	success := resp.StatusCode >= 200 && resp.StatusCode < 300
	return &ExecuteToolResult{
		Success: success,
		Data:    resultData,
	}, nil
}

// buildRequestBody renders the Go template with params to produce the HTTP request body.
func buildRequestBody(templateStr string, params map[string]interface{}) ([]byte, error) {
	if templateStr == "" {
		// No template — send params as JSON directly
		return json.Marshal(params)
	}

	tmpl, err := template.New("request").Parse(templateStr)
	if err != nil {
		return nil, fmt.Errorf("parse request template: %w", err)
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, params); err != nil {
		return nil, fmt.Errorf("execute request template: %w", err)
	}
	return buf.Bytes(), nil
}

// parseResponseTemplate renders the response template with the raw response body.
func parseResponseTemplate(templateStr string, rawBody []byte) (interface{}, error) {
	// Parse the raw body as a map for template rendering
	var data interface{}
	if err := json.Unmarshal(rawBody, &data); err != nil {
		data = map[string]interface{}{"raw": string(rawBody)}
	}

	tmpl, err := template.New("response").Parse(templateStr)
	if err != nil {
		return nil, fmt.Errorf("parse response template: %w", err)
	}

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

	// Try to parse the rendered template output as JSON
	var result interface{}
	rendered := buf.Bytes()
	if err := json.Unmarshal(rendered, &result); err != nil {
		return string(rendered), nil
	}
	return result, nil
}

// applyAuth sets authentication headers on the HTTP request based on tool config.
func applyAuth(req *http.Request, tool *model.CaptainCustomTool) error {
	switch tool.AuthType {
	case model.ToolAuthTypeNone:
		// No auth required
		return nil
	case model.ToolAuthTypeBasic:
		var authCfg struct {
			Username string `json:"username"`
			Password string `json:"password"`
		}
		if err := json.Unmarshal(tool.AuthConfig, &authCfg); err != nil {
			return fmt.Errorf("parse basic auth config: %w", err)
		}
		req.SetBasicAuth(authCfg.Username, authCfg.Password)
		return nil
	case model.ToolAuthTypeBearer:
		var authCfg struct {
			Token string `json:"token"`
		}
		if err := json.Unmarshal(tool.AuthConfig, &authCfg); err != nil {
			return fmt.Errorf("parse bearer auth config: %w", err)
		}
		req.Header.Set("Authorization", "Bearer "+authCfg.Token)
		return nil
	case model.ToolAuthTypeApiKey:
		var authCfg struct {
			Key   string `json:"key"`
			Value string `json:"value"`
			Header string `json:"header"` // default: "X-API-Key"
		}
		if err := json.Unmarshal(tool.AuthConfig, &authCfg); err != nil {
			return fmt.Errorf("parse api_key auth config: %w", err)
		}
		headerName := authCfg.Header
		if headerName == "" {
			headerName = "X-API-Key"
		}
		req.Header.Set(headerName, authCfg.Value)
		return nil
	default:
		return fmt.Errorf("unsupported auth type: %s", tool.AuthType)
	}
}

// --- Tool Testing ---
// Reference: Chatwoot Captain::CustomToolsController#test
// TestTool allows testing a custom tool with parameters before enabling it.
// Unlike ExecuteTool, TestTool does not require the tool to be enabled
// and returns detailed error information for debugging.

// TestToolRequest is the DTO for testing a custom tool.
type TestToolRequest struct {
	ToolID uint                   `json:"tool_id" validate:"required"`
	Params map[string]interface{} `json:"params"`
}

// TestTool tests a custom tool with given parameters without requiring it to be enabled.
func (s *CaptainCustomToolService) TestTool(ctx context.Context, accountID uint, req *TestToolRequest) (*ExecuteToolResult, error) {
	tool, err := s.toolRepo.GetByID(ctx, req.ToolID)
	if err != nil {
		return nil, fmt.Errorf("custom tool not found: %w", err)
	}

	// Verify the tool belongs to the specified account
	if tool.AccountID != accountID {
		return nil, fmt.Errorf("custom tool does not belong to this account")
	}

	// TestTool can execute even disabled tools (for validation before enabling)
	result, err := s.ExecuteTool(ctx, req.ToolID, req.Params)
	if err != nil {
		return &ExecuteToolResult{
			Success: false,
			Error:   fmt.Sprintf("test execution failed: %v", err),
		}, nil
	}
	return result, nil
}