server/tm/git_tm/git_task_manager.go

package git_tm

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/iomodo/staff/git"
	"github.com/iomodo/staff/tm"
	"gopkg.in/yaml.v3"
)

// GitTaskManager implements TaskManager interface using git as the source of truth
type GitTaskManager struct {
	git      git.GitInterface
	repoPath string
	tasksDir string
}

// NewGitTaskManager creates a new GitTaskManager instance
func NewGitTaskManager(git git.GitInterface, repoPath string) *GitTaskManager {
	return &GitTaskManager{
		git:      git,
		repoPath: repoPath,
		tasksDir: filepath.Join(repoPath, "tasks"),
	}
}

// ensureTasksDir ensures the tasks directory exists
func (gtm *GitTaskManager) ensureTasksDir() error {
	if err := os.MkdirAll(gtm.tasksDir, 0755); err != nil {
		return fmt.Errorf("failed to create tasks directory: %w", err)
	}
	return nil
}

// generateTaskID generates a unique task ID
func (gtm *GitTaskManager) generateTaskID() string {
	timestamp := time.Now().Unix()
	random := uuid.New().String()[:8]
	return fmt.Sprintf("task-%d-%s", timestamp, random)
}

// taskToMarkdown converts a Task to markdown format
func (gtm *GitTaskManager) taskToMarkdown(task *tm.Task) (string, error) {
	// Create frontmatter data
	frontmatter := map[string]interface{}{
		"id":          task.ID,
		"title":       task.Title,
		"description": task.Description,
		"owner_id":    task.Owner.ID,
		"owner_name":  task.Owner.Name,
		"status":      task.Status,
		"priority":    task.Priority,
		"created_at":  task.CreatedAt.Format(time.RFC3339),
		"updated_at":  task.UpdatedAt.Format(time.RFC3339),
	}

	if task.DueDate != nil {
		frontmatter["due_date"] = task.DueDate.Format(time.RFC3339)
	}
	if task.CompletedAt != nil {
		frontmatter["completed_at"] = task.CompletedAt.Format(time.RFC3339)
	}
	if task.ArchivedAt != nil {
		frontmatter["archived_at"] = task.ArchivedAt.Format(time.RFC3339)
	}

	// Marshal frontmatter to YAML
	yamlData, err := yaml.Marshal(frontmatter)
	if err != nil {
		return "", fmt.Errorf("failed to marshal frontmatter: %w", err)
	}

	// Build markdown content
	var content strings.Builder
	content.WriteString("---\n")
	content.Write(yamlData)
	content.WriteString("---\n\n")

	if task.Description != "" {
		content.WriteString("# Task Description\n\n")
		content.WriteString(task.Description)
		content.WriteString("\n\n")
	}

	return content.String(), nil
}

// parseTaskFromMarkdown parses a Task from markdown format
func (gtm *GitTaskManager) parseTaskFromMarkdown(content string) (*tm.Task, error) {
	// Split content into frontmatter and body
	parts := strings.SplitN(content, "---\n", 3)
	if len(parts) < 3 {
		return nil, fmt.Errorf("invalid markdown format: missing frontmatter")
	}

	// Parse YAML frontmatter
	var frontmatter map[string]interface{}
	if err := yaml.Unmarshal([]byte(parts[1]), &frontmatter); err != nil {
		return nil, fmt.Errorf("failed to parse frontmatter: %w", err)
	}

	// Extract task data
	task := &tm.Task{}

	if id, ok := frontmatter["id"].(string); ok {
		task.ID = id
	}
	if title, ok := frontmatter["title"].(string); ok {
		task.Title = title
	}
	if description, ok := frontmatter["description"].(string); ok {
		task.Description = description
	}
	if ownerID, ok := frontmatter["owner_id"].(string); ok {
		task.Owner.ID = ownerID
	}
	if ownerName, ok := frontmatter["owner_name"].(string); ok {
		task.Owner.Name = ownerName
	}
	if status, ok := frontmatter["status"].(string); ok {
		task.Status = tm.TaskStatus(status)
	}
	if priority, ok := frontmatter["priority"].(string); ok {
		task.Priority = tm.TaskPriority(priority)
	}

	// Parse timestamps
	if createdAt, ok := frontmatter["created_at"].(string); ok {
		if t, err := time.Parse(time.RFC3339, createdAt); err == nil {
			task.CreatedAt = t
		}
	}
	if updatedAt, ok := frontmatter["updated_at"].(string); ok {
		if t, err := time.Parse(time.RFC3339, updatedAt); err == nil {
			task.UpdatedAt = t
		}
	}
	if dueDate, ok := frontmatter["due_date"].(string); ok {
		if t, err := time.Parse(time.RFC3339, dueDate); err == nil {
			task.DueDate = &t
		}
	}
	if completedAt, ok := frontmatter["completed_at"].(string); ok {
		if t, err := time.Parse(time.RFC3339, completedAt); err == nil {
			task.CompletedAt = &t
		}
	}
	if archivedAt, ok := frontmatter["archived_at"].(string); ok {
		if t, err := time.Parse(time.RFC3339, archivedAt); err == nil {
			task.ArchivedAt = &t
		}
	}

	return task, nil
}

// readTaskFile reads a task from a file
func (gtm *GitTaskManager) readTaskFile(taskID string) (*tm.Task, error) {
	filePath := filepath.Join(gtm.tasksDir, taskID+".md")

	content, err := os.ReadFile(filePath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, tm.ErrTaskNotFound
		}
		return nil, fmt.Errorf("failed to read task file: %w", err)
	}

	return gtm.parseTaskFromMarkdown(string(content))
}

// writeTaskFile writes a task to a file
func (gtm *GitTaskManager) writeTaskFile(task *tm.Task) error {
	content, err := gtm.taskToMarkdown(task)
	if err != nil {
		return fmt.Errorf("failed to convert task to markdown: %w", err)
	}

	filePath := filepath.Join(gtm.tasksDir, task.ID+".md")
	if err := os.WriteFile(filePath, []byte(content), 0644); err != nil {
		return fmt.Errorf("failed to write task file: %w", err)
	}

	return nil
}

// listTaskFiles returns all task file paths
func (gtm *GitTaskManager) listTaskFiles() ([]string, error) {
	entries, err := os.ReadDir(gtm.tasksDir)
	if err != nil {
		if os.IsNotExist(err) {
			return []string{}, nil
		}
		return nil, fmt.Errorf("failed to read tasks directory: %w", err)
	}

	var taskFiles []string
	for _, entry := range entries {
		if !entry.IsDir() && strings.HasSuffix(entry.Name(), ".md") {
			taskID := strings.TrimSuffix(entry.Name(), ".md")
			taskFiles = append(taskFiles, taskID)
		}
	}

	return taskFiles, nil
}

// commitTaskChange commits a task change to git
func (gtm *GitTaskManager) commitTaskChange(taskID, operation string) error {
	ctx := context.Background()

	// Add the task file
	if err := gtm.git.Add(ctx, []string{filepath.Join("tasks", taskID+".md")}); err != nil {
		return fmt.Errorf("failed to add task file: %w", err)
	}

	// Commit the change
	message := fmt.Sprintf("task: %s - %s", taskID, operation)
	if err := gtm.git.Commit(ctx, message, git.CommitOptions{}); err != nil {
		return fmt.Errorf("failed to commit task change: %w", err)
	}

	return nil
}

// CreateTask creates a new task
func (gtm *GitTaskManager) CreateTask(ctx context.Context, req *tm.TaskCreateRequest) (*tm.Task, error) {
	if err := gtm.ensureTasksDir(); err != nil {
		return nil, err
	}

	// Validate request
	if req.Title == "" {
		return nil, tm.ErrInvalidTaskData
	}
	if req.OwnerID == "" {
		return nil, tm.ErrInvalidOwner
	}

	// Generate task ID
	taskID := gtm.generateTaskID()
	now := time.Now()

	// Create task
	task := &tm.Task{
		ID:          taskID,
		Title:       req.Title,
		Description: req.Description,
		Owner: tm.Owner{
			ID:   req.OwnerID,
			Name: req.OwnerID, // TODO: Look up owner name from a user service
		},
		Status:    tm.StatusToDo,
		Priority:  req.Priority,
		CreatedAt: now,
		UpdatedAt: now,
		DueDate:   req.DueDate,
	}

	// Write task file
	if err := gtm.writeTaskFile(task); err != nil {
		return nil, err
	}

	// Commit to git
	if err := gtm.commitTaskChange(taskID, "created"); err != nil {
		return nil, err
	}

	return task, nil
}

// GetTask retrieves a task by ID
func (gtm *GitTaskManager) GetTask(ctx context.Context, id string) (*tm.Task, error) {
	return gtm.readTaskFile(id)
}

// UpdateTask updates an existing task
func (gtm *GitTaskManager) UpdateTask(ctx context.Context, id string, req *tm.TaskUpdateRequest) (*tm.Task, error) {
	// Read existing task
	task, err := gtm.readTaskFile(id)
	if err != nil {
		return nil, err
	}

	// Update fields
	updated := false
	if req.Title != nil {
		task.Title = *req.Title
		updated = true
	}
	if req.Description != nil {
		task.Description = *req.Description
		updated = true
	}
	if req.OwnerID != nil {
		task.Owner.ID = *req.OwnerID
		task.Owner.Name = *req.OwnerID // TODO: Look up owner name from a user service
		updated = true
	}
	if req.Status != nil {
		task.Status = *req.Status
		updated = true
	}
	if req.Priority != nil {
		task.Priority = *req.Priority
		updated = true
	}
	if req.DueDate != nil {
		task.DueDate = req.DueDate
		updated = true
	}

	if !updated {
		return task, nil
	}

	// Update timestamps
	task.UpdatedAt = time.Now()

	// Handle status-specific timestamps
	if req.Status != nil {
		switch *req.Status {
		case tm.StatusCompleted:
			if task.CompletedAt == nil {
				now := time.Now()
				task.CompletedAt = &now
			}
		case tm.StatusArchived:
			if task.ArchivedAt == nil {
				now := time.Now()
				task.ArchivedAt = &now
			}
		}
	}

	// Write updated task
	if err := gtm.writeTaskFile(task); err != nil {
		return nil, err
	}

	// Commit to git
	if err := gtm.commitTaskChange(id, "updated"); err != nil {
		return nil, err
	}

	return task, nil
}

// ArchiveTask archives a task
func (gtm *GitTaskManager) ArchiveTask(ctx context.Context, id string) error {
	status := tm.StatusArchived
	req := &tm.TaskUpdateRequest{
		Status: &status,
	}

	_, err := gtm.UpdateTask(ctx, id, req)
	return err
}

// ListTasks lists tasks with filtering and pagination
func (gtm *GitTaskManager) ListTasks(ctx context.Context, filter *tm.TaskFilter, page, pageSize int) (*tm.TaskList, error) {
	// Get all task files
	taskFiles, err := gtm.listTaskFiles()
	if err != nil {
		return nil, err
	}

	// Read all tasks
	var tasks []*tm.Task
	for _, taskID := range taskFiles {
		task, err := gtm.readTaskFile(taskID)
		if err != nil {
			continue // Skip corrupted files
		}
		tasks = append(tasks, task)
	}

	// Apply filters
	if filter != nil {
		tasks = gtm.filterTasks(tasks, filter)
	}

	// Sort by creation date (newest first)
	sort.Slice(tasks, func(i, j int) bool {
		return tasks[i].CreatedAt.After(tasks[j].CreatedAt)
	})

	// Apply pagination
	totalCount := len(tasks)
	start := page * pageSize
	end := start + pageSize

	if start >= totalCount {
		return &tm.TaskList{
			Tasks:      []*tm.Task{},
			TotalCount: totalCount,
			Page:       page,
			PageSize:   pageSize,
			HasMore:    false,
		}, nil
	}

	if end > totalCount {
		end = totalCount
	}

	return &tm.TaskList{
		Tasks:      tasks[start:end],
		TotalCount: totalCount,
		Page:       page,
		PageSize:   pageSize,
		HasMore:    end < totalCount,
	}, nil
}

// filterTasks applies filters to a list of tasks
func (gtm *GitTaskManager) filterTasks(tasks []*tm.Task, filter *tm.TaskFilter) []*tm.Task {
	var filtered []*tm.Task

	for _, task := range tasks {
		if gtm.taskMatchesFilter(task, filter) {
			filtered = append(filtered, task)
		}
	}

	return filtered
}

// taskMatchesFilter checks if a task matches the given filter
func (gtm *GitTaskManager) taskMatchesFilter(task *tm.Task, filter *tm.TaskFilter) bool {
	if filter.OwnerID != nil && task.Owner.ID != *filter.OwnerID {
		return false
	}
	if filter.Status != nil && task.Status != *filter.Status {
		return false
	}
	if filter.Priority != nil && task.Priority != *filter.Priority {
		return false
	}
	if filter.DueBefore != nil && (task.DueDate == nil || !task.DueDate.Before(*filter.DueBefore)) {
		return false
	}
	if filter.DueAfter != nil && (task.DueDate == nil || !task.DueDate.After(*filter.DueAfter)) {
		return false
	}
	if filter.CreatedAfter != nil && !task.CreatedAt.After(*filter.CreatedAfter) {
		return false
	}
	if filter.CreatedBefore != nil && !task.CreatedAt.Before(*filter.CreatedBefore) {
		return false
	}

	return true
}

// StartTask starts a task (changes status to in_progress)
func (gtm *GitTaskManager) StartTask(ctx context.Context, id string) (*tm.Task, error) {
	status := tm.StatusInProgress
	req := &tm.TaskUpdateRequest{
		Status: &status,
	}

	return gtm.UpdateTask(ctx, id, req)
}

// CompleteTask completes a task (changes status to completed)
func (gtm *GitTaskManager) CompleteTask(ctx context.Context, id string) (*tm.Task, error) {
	status := tm.StatusCompleted
	req := &tm.TaskUpdateRequest{
		Status: &status,
	}

	return gtm.UpdateTask(ctx, id, req)
}

// GetTasksByOwner gets tasks for a specific owner
func (gtm *GitTaskManager) GetTasksByOwner(ctx context.Context, ownerID string, page, pageSize int) (*tm.TaskList, error) {
	filter := &tm.TaskFilter{
		OwnerID: &ownerID,
	}
	return gtm.ListTasks(ctx, filter, page, pageSize)
}

// GetTasksByStatus gets tasks with a specific status
func (gtm *GitTaskManager) GetTasksByStatus(ctx context.Context, status tm.TaskStatus, page, pageSize int) (*tm.TaskList, error) {
	filter := &tm.TaskFilter{
		Status: &status,
	}
	return gtm.ListTasks(ctx, filter, page, pageSize)
}

// GetTasksByPriority gets tasks with a specific priority
func (gtm *GitTaskManager) GetTasksByPriority(ctx context.Context, priority tm.TaskPriority, page, pageSize int) (*tm.TaskList, error) {
	filter := &tm.TaskFilter{
		Priority: &priority,
	}
	return gtm.ListTasks(ctx, filter, page, pageSize)
}

// Ensure GitTaskManager implements TaskManager interface
var _ tm.TaskManager = (*GitTaskManager)(nil)