package agent

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/iomodo/staff/git"
	"github.com/iomodo/staff/llm"
	_ "github.com/iomodo/staff/llm/openai" // Import for side effects (registers provider)
	"github.com/iomodo/staff/tm"
)

// AgentConfig contains configuration for the agent
type AgentConfig struct {
	Name        string
	Role        string
	GitUsername string
	GitEmail    string
	WorkingDir  string

	// LLM Configuration
	LLMProvider llm.Provider
	LLMModel    string
	LLMConfig   llm.Config

	// System prompt for the agent
	SystemPrompt string

	// Task Manager Configuration
	TaskManager tm.TaskManager

	// Git Configuration
	GitRepoPath string
	GitRemote   string
	GitBranch   string

	// Gerrit Configuration
	GerritEnabled bool
	GerritConfig  GerritConfig
}

// GerritConfig holds configuration for Gerrit operations
type GerritConfig struct {
	Username string
	Password string // Can be HTTP password or API token
	BaseURL  string
	Project  string
}

// Agent represents an AI agent that can process tasks
type Agent struct {
	Config       AgentConfig
	llmProvider  llm.LLMProvider
	gitInterface git.GitInterface
	ctx          context.Context
	cancel       context.CancelFunc
	logger       *slog.Logger
}

// NewAgent creates a new agent instance
func NewAgent(config AgentConfig, logger *slog.Logger) (*Agent, error) {
	// Validate configuration
	if err := validateConfig(config); err != nil {
		return nil, fmt.Errorf("invalid config: %w", err)
	}

	// Create LLM provider
	llmProvider, err := llm.CreateProvider(config.LLMConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to create LLM provider: %w", err)
	}

	// Create git interface
	var gitInterface git.GitInterface
	if config.GerritEnabled {
		// Create Gerrit pull request provider
		gerritPRProvider := git.NewGerritPullRequestProvider(config.GerritConfig.Project, git.GerritConfig{
			Username:   config.GerritConfig.Username,
			Password:   config.GerritConfig.Password,
			BaseURL:    config.GerritConfig.BaseURL,
			HTTPClient: nil, // Will use default client
		})

		// Create git interface with Gerrit pull request provider
		gitConfig := git.GitConfig{
			Timeout:             30 * time.Second,
			PullRequestProvider: gerritPRProvider,
		}
		gitInterface = git.NewGitWithPullRequests(config.GitRepoPath, gitConfig, gerritPRProvider, logger)
	} else {
		// Use default git interface (GitHub)
		gitInterface = git.DefaultGit(config.GitRepoPath)
	}

	// Create context with cancellation
	ctx, cancel := context.WithCancel(context.Background())

	agent := &Agent{
		Config:       config,
		llmProvider:  llmProvider,
		gitInterface: gitInterface,
		ctx:          ctx,
		cancel:       cancel,
		logger:       logger,
	}

	return agent, nil
}

// validateConfig validates the agent configuration
func validateConfig(config AgentConfig) error {
	if config.Name == "" {
		return fmt.Errorf("agent name is required")
	}
	if config.Role == "" {
		return fmt.Errorf("agent role is required")
	}
	if config.WorkingDir == "" {
		return fmt.Errorf("working directory is required")
	}
	if config.SystemPrompt == "" {
		return fmt.Errorf("system prompt is required")
	}
	if config.TaskManager == nil {
		return fmt.Errorf("task manager is required")
	}
	if config.GitRepoPath == "" {
		return fmt.Errorf("git repository path is required")
	}
	return nil
}

const (
	// Agent polling intervals
	TaskPollingInterval       = 60 * time.Second
	ErrorRetryInterval        = 30 * time.Second
	DefaultGitTimeout         = 30 * time.Second
	DefaultContextTimeout     = 5 * time.Minute
	DefaultMaxTaskRetries     = 3
	DefaultLLMMaxTokens       = 4000
	DefaultLLMTemperature     = 0.7
)

// Run starts the agent's main loop
func (a *Agent) Run() error {
	a.logger.Info("Starting agent", slog.String("name", a.Config.Name), slog.String("role", a.Config.Role))
	defer a.logger.Info("Agent stopped", slog.String("name", a.Config.Name))

	// Initialize git repository if needed
	if err := a.initializeGit(); err != nil {
		return fmt.Errorf("failed to initialize git: %w", err)
	}

	// Main agent loop
	for {
		select {
		case <-a.ctx.Done():
			return a.ctx.Err()
		default:
			if err := a.processNextTask(); err != nil {
				a.logger.Error("Error processing task", slog.String("error", err.Error()))
				time.Sleep(ErrorRetryInterval)
			}
		}
	}
}

// Stop stops the agent
func (a *Agent) Stop() {
	a.logger.Info("Stopping agent", slog.String("name", a.Config.Name))
	a.cancel()
	if a.llmProvider != nil {
		a.llmProvider.Close()
	}
}

// initializeGit initializes the git repository
func (a *Agent) initializeGit() error {
	ctx := context.Background()

	if err := a.ensureRepository(ctx); err != nil {
		return err
	}

	if err := a.ensureRemoteOrigin(ctx); err != nil {
		return err
	}

	if err := a.ensureTargetBranch(ctx); err != nil {
		return err
	}

	return nil
}

// ensureRepository ensures the git repository is initialized
func (a *Agent) ensureRepository(ctx context.Context) error {
	isRepo, err := a.gitInterface.IsRepository(ctx, a.Config.GitRepoPath)
	if err != nil {
		return fmt.Errorf("failed to check repository: %w", err)
	}

	if !isRepo {
		if err := a.gitInterface.Init(ctx, a.Config.GitRepoPath); err != nil {
			return fmt.Errorf("failed to initialize repository: %w", err)
		}
	}

	return nil
}

// ensureRemoteOrigin ensures the remote origin is configured
func (a *Agent) ensureRemoteOrigin(ctx context.Context) error {
	remotes, err := a.gitInterface.ListRemotes(ctx)
	if err != nil {
		return fmt.Errorf("failed to list remotes: %w", err)
	}

	// Check if origin already exists
	for _, remote := range remotes {
		if remote.Name == "origin" {
			return nil
		}
	}

	// Add remote origin
	remoteURL := a.buildRemoteURL()
	if err := a.gitInterface.AddRemote(ctx, "origin", remoteURL); err != nil {
		return fmt.Errorf("failed to add remote origin: %w", err)
	}

	return nil
}

// buildRemoteURL builds the appropriate remote URL based on configuration
func (a *Agent) buildRemoteURL() string {
	if !a.Config.GerritEnabled {
		return a.Config.GitRemote
	}

	// Build Gerrit URL
	if strings.HasPrefix(a.Config.GerritConfig.BaseURL, "https://") {
		return fmt.Sprintf("%s/%s.git", a.Config.GerritConfig.BaseURL, a.Config.GerritConfig.Project)
	}

	// SSH format
	return fmt.Sprintf("ssh://%s@%s:29418/%s.git",
		a.Config.GerritConfig.Username,
		strings.TrimPrefix(a.Config.GerritConfig.BaseURL, "https://"),
		a.Config.GerritConfig.Project)
}

// ensureTargetBranch ensures the agent is on the target branch
func (a *Agent) ensureTargetBranch(ctx context.Context) error {
	if a.Config.GitBranch == "" {
		return nil
	}

	currentBranch, err := a.gitInterface.GetCurrentBranch(ctx)
	if err != nil {
		return fmt.Errorf("failed to get current branch: %w", err)
	}

	if currentBranch == a.Config.GitBranch {
		a.logger.Info("Already on target branch", slog.String("branch", a.Config.GitBranch))
		return nil
	}

	return a.checkoutOrCreateBranch(ctx, a.Config.GitBranch)
}

// checkoutOrCreateBranch attempts to checkout a branch, creating it if it doesn't exist
func (a *Agent) checkoutOrCreateBranch(ctx context.Context, branchName string) error {
	if err := a.gitInterface.Checkout(ctx, branchName); err != nil {
		if a.isBranchNotFoundError(err) {
			if createErr := a.gitInterface.CreateBranch(ctx, branchName, ""); createErr != nil {
				return fmt.Errorf("failed to create branch %s: %w", branchName, createErr)
			}
			return nil
		}
		return fmt.Errorf("failed to checkout branch %s: %w", branchName, err)
	}
	return nil
}

// isBranchNotFoundError checks if the error indicates a branch doesn't exist
func (a *Agent) isBranchNotFoundError(err error) bool {
	errMsg := err.Error()
	return strings.Contains(errMsg, "did not match any file(s) known to git") ||
		strings.Contains(errMsg, "not found") ||
		strings.Contains(errMsg, "unknown revision") ||
		strings.Contains(errMsg, "reference is not a tree") ||
		strings.Contains(errMsg, "pathspec") ||
		strings.Contains(errMsg, "fatal: invalid reference")
}

// processNextTask processes the next available task
func (a *Agent) processNextTask() error {
	ctx := context.Background()

	// Get tasks assigned to this agent
	taskList, err := a.Config.TaskManager.GetTasksByOwner(ctx, a.Config.Name, 0, 10)
	a.logger.Info("Total number of Tasks", slog.String("agent", a.Config.Name), slog.Any("tasks", taskList.TotalCount))
	if err != nil {
		return fmt.Errorf("failed to get tasks: %w", err)
	}

	// Find a task that's ready to be worked on
	var taskToProcess *tm.Task
	for _, task := range taskList.Tasks {
		if task.Status == tm.StatusToDo {
			taskToProcess = task
			break
		}
	}

	a.logger.Info("Task to process", slog.Any("task", taskToProcess))

	if taskToProcess == nil {
		// No tasks to process, wait a bit
		time.Sleep(TaskPollingInterval)
		return nil
	}

	a.logger.Info("Processing task", slog.String("id", taskToProcess.ID), slog.String("title", taskToProcess.Title))

	// Start the task
	startedTask, err := a.Config.TaskManager.StartTask(ctx, taskToProcess.ID)
	if err != nil {
		return fmt.Errorf("failed to start task: %w", err)
	}

	// Process the task with LLM
	solution, err := a.processTaskWithLLM(startedTask)
	if err != nil {
		// Mark task as failed or retry
		a.logger.Error("Failed to process task with LLM", slog.String("error", err.Error()))
		return err
	}

	// Create PR with the solution
	if err := a.createPullRequest(startedTask, solution); err != nil {
		return fmt.Errorf("failed to create pull request: %w", err)
	}

	// Complete the task
	if _, err := a.Config.TaskManager.CompleteTask(ctx, startedTask.ID); err != nil {
		return fmt.Errorf("failed to complete task: %w", err)
	}

	a.logger.Info("Successfully completed task", slog.String("id", startedTask.ID))
	return nil
}

// processTaskWithLLM sends the task to the LLM and gets a solution
func (a *Agent) processTaskWithLLM(task *tm.Task) (string, error) {
	ctx := context.Background()

	// Prepare the prompt
	prompt := a.buildTaskPrompt(task)

	// Create chat completion request
	req := llm.ChatCompletionRequest{
		Model: a.Config.LLMModel,
		Messages: []llm.Message{
			{
				Role:    llm.RoleSystem,
				Content: a.Config.SystemPrompt,
			},
			{
				Role:    llm.RoleUser,
				Content: prompt,
			},
		},
		MaxTokens:   intPtr(DefaultLLMMaxTokens),
		Temperature: float64Ptr(DefaultLLMTemperature),
	}

	// Get response from LLM
	resp, err := a.llmProvider.ChatCompletion(ctx, req)
	if err != nil {
		return "", fmt.Errorf("LLM chat completion failed: %w", err)
	}

	if len(resp.Choices) == 0 {
		return "", fmt.Errorf("no response from LLM")
	}

	return resp.Choices[0].Message.Content, nil
}

// buildTaskPrompt builds the prompt for the LLM based on the task
func (a *Agent) buildTaskPrompt(task *tm.Task) string {
	var prompt strings.Builder

	prompt.WriteString(fmt.Sprintf("Task ID: %s\n", task.ID))
	prompt.WriteString(fmt.Sprintf("Title: %s\n", task.Title))
	prompt.WriteString(fmt.Sprintf("Priority: %s\n", task.Priority))

	if task.Description != "" {
		prompt.WriteString(fmt.Sprintf("Description: %s\n", task.Description))
	}

	if task.DueDate != nil {
		prompt.WriteString(fmt.Sprintf("Due Date: %s\n", task.DueDate.Format("2006-01-02")))
	}

	prompt.WriteString("\nPlease provide a detailed solution for this task. ")
	prompt.WriteString("Include any code, documentation, or other deliverables as needed. ")
	prompt.WriteString("Format your response appropriately for the type of task.")

	return prompt.String()
}

// createPullRequest creates a pull request with the solution
func (a *Agent) createPullRequest(task *tm.Task, solution string) error {
	ctx := context.Background()

	// Generate branch name
	branchName := a.generateBranchName(task)

	// Create and checkout to new branch
	if err := a.gitInterface.CreateBranch(ctx, branchName, ""); err != nil {
		return fmt.Errorf("failed to create branch: %w", err)
	}

	if err := a.gitInterface.Checkout(ctx, branchName); err != nil {
		return fmt.Errorf("failed to checkout branch: %w", err)
	}

	// Create solution file
	solutionPath := filepath.Join(a.Config.WorkingDir, fmt.Sprintf("task-%s-solution.md", task.ID))
	solutionContent := a.formatSolution(task, solution)

	if err := os.WriteFile(solutionPath, []byte(solutionContent), 0644); err != nil {
		return fmt.Errorf("failed to write solution file: %w", err)
	}

	// Add and commit the solution
	if err := a.gitInterface.Add(ctx, []string{solutionPath}); err != nil {
		return fmt.Errorf("failed to add solution file: %w", err)
	}

	commitMessage := fmt.Sprintf("feat: Complete task %s - %s\n\n%s", task.ID, task.Title, a.formatPullRequestDescription(task, solution))
	if err := a.gitInterface.Commit(ctx, commitMessage, git.CommitOptions{
		Author: &git.Author{
			Name:  a.Config.GitUsername,
			Email: a.Config.GitEmail,
			Time:  time.Now(),
		},
	}); err != nil {
		return fmt.Errorf("failed to commit solution: %w", err)
	}

	if a.Config.GerritEnabled {
		// For Gerrit: Push to refs/for/BRANCH to create a change
		gerritRef := fmt.Sprintf("refs/for/%s", a.Config.GitBranch)
		if err := a.gitInterface.Push(ctx, "origin", gerritRef, git.PushOptions{}); err != nil {
			return fmt.Errorf("failed to push to Gerrit: %w", err)
		}
		a.logger.Info("Created Gerrit change for task", slog.String("id", task.ID), slog.String("ref", gerritRef))
	} else {
		// For GitHub: Push branch and create PR
		if err := a.gitInterface.Push(ctx, "origin", branchName, git.PushOptions{SetUpstream: true}); err != nil {
			return fmt.Errorf("failed to push branch: %w", err)
		}

		// Create pull request using the git interface
		prOptions := git.PullRequestOptions{
			Title:       fmt.Sprintf("Complete task %s: %s", task.ID, task.Title),
			Description: a.formatPullRequestDescription(task, solution),
			BaseBranch:  a.Config.GitBranch,
			HeadBranch:  branchName,
			BaseRepo:    a.Config.GerritConfig.Project,
			HeadRepo:    a.Config.GerritConfig.Project,
		}

		pr, err := a.gitInterface.CreatePullRequest(ctx, prOptions)
		if err != nil {
			return fmt.Errorf("failed to create pull request: %w", err)
		}

		a.logger.Info("Created pull request for task", slog.String("id", task.ID), slog.String("title", pr.Title), slog.String("pr_id", pr.ID))
	}

	return nil
}

// generateBranchName generates a branch name for the task
func (a *Agent) generateBranchName(task *tm.Task) string {
	// Clean the task title for branch name
	cleanTitle := strings.ReplaceAll(task.Title, " ", "-")
	cleanTitle = strings.ToLower(cleanTitle)

	// Remove special characters that are not allowed in git branch names
	// Keep only alphanumeric characters and hyphens
	var result strings.Builder
	for _, char := range cleanTitle {
		if (char >= 'a' && char <= 'z') || (char >= '0' && char <= '9') || char == '-' {
			result.WriteRune(char)
		}
	}
	cleanTitle = result.String()

	// Remove consecutive hyphens
	for strings.Contains(cleanTitle, "--") {
		cleanTitle = strings.ReplaceAll(cleanTitle, "--", "-")
	}

	// Remove leading and trailing hyphens
	cleanTitle = strings.Trim(cleanTitle, "-")

	// Limit length
	if len(cleanTitle) > 50 {
		cleanTitle = cleanTitle[:50]
		// Ensure we don't end with a hyphen after truncation
		cleanTitle = strings.TrimSuffix(cleanTitle, "-")
	}

	return fmt.Sprintf("task/%s-%s", task.ID, cleanTitle)
}

// formatSolution formats the solution for the pull request
func (a *Agent) formatSolution(task *tm.Task, solution string) string {
	var content strings.Builder

	content.WriteString(fmt.Sprintf("# Task Solution: %s\n\n", task.Title))
	content.WriteString(fmt.Sprintf("**Task ID:** %s\n", task.ID))
	content.WriteString(fmt.Sprintf("**Agent:** %s (%s)\n", a.Config.Name, a.Config.Role))
	content.WriteString(fmt.Sprintf("**Completed:** %s\n\n", time.Now().Format("2006-01-02 15:04:05")))

	content.WriteString("## Task Description\n\n")
	content.WriteString(task.Description)
	content.WriteString("\n\n")

	content.WriteString("## Solution\n\n")
	content.WriteString(solution)
	content.WriteString("\n\n")

	content.WriteString("---\n")
	content.WriteString("*This solution was generated by AI Agent*\n")

	return content.String()
}

// formatPullRequestDescription formats the description for the pull request
func (a *Agent) formatPullRequestDescription(task *tm.Task, solution string) string {
	var content strings.Builder

	content.WriteString(fmt.Sprintf("**Task ID:** %s\n", task.ID))
	content.WriteString(fmt.Sprintf("**Title:** %s\n", task.Title))
	content.WriteString(fmt.Sprintf("**Priority:** %s\n", task.Priority))

	if task.Description != "" {
		content.WriteString(fmt.Sprintf("**Description:** %s\n", task.Description))
	}

	if task.DueDate != nil {
		content.WriteString(fmt.Sprintf("**Due Date:** %s\n", task.DueDate.Format("2006-01-02")))
	}

	content.WriteString("\n**Solution:**\n\n")
	content.WriteString(solution)

	return content.String()
}

// ptr helpers for cleaner code
func intPtr(i int) *int {
	return &i
}

func float64Ptr(f float64) *float64 {
	return &f
}