"""
Task Manager MCP Server - A comprehensive example for learning MCP development

This server provides task management functionality with multiple tools:
- Create, read, update, delete tasks
- List tasks with filtering
- Mark tasks as complete/incomplete
- Add tags and priorities
- Search functionality

Perfect for learning MCP concepts and extending with new features!
"""

import json
import os
from datetime import datetime
from typing import Any, Dict, List, Optional
from enum import Enum

from mcp.server.fastmcp import FastMCP
from pydantic import BaseModel

# Initialize FastMCP server
mcp = FastMCP("task-manager")

# Data models
class Priority(str, Enum):
    LOW = "low"
    MEDIUM = "medium"
    HIGH = "high"
    URGENT = "urgent"

class TaskStatus(str, Enum):
    PENDING = "pending"
    IN_PROGRESS = "in_progress"
    COMPLETED = "completed"
    CANCELLED = "cancelled"

class Task(BaseModel):
    id: int
    title: str
    description: str = ""
    status: TaskStatus = TaskStatus.PENDING
    priority: Priority = Priority.MEDIUM
    tags: List[str] = []
    created_at: str
    updated_at: str
    due_date: Optional[str] = None
    completed_at: Optional[str] = None

# In-memory storage (in a real app, you'd use a database)
tasks_db: Dict[int, Task] = {}
next_task_id = 1

# File-based persistence
DATA_FILE = "tasks.json"

def load_tasks():
    """Load tasks from file if it exists"""
    global tasks_db, next_task_id
    
    if os.path.exists(DATA_FILE):
        try:
            with open(DATA_FILE, 'r') as f:
                data = json.load(f)
                tasks_db = {int(k): Task(**v) for k, v in data.get('tasks', {}).items()}
                next_task_id = data.get('next_id', 1)
        except Exception as e:
            print(f"Error loading tasks: {e}")

def save_tasks():
    """Save tasks to file"""
    try:
        data = {
            'tasks': {str(k): v.model_dump() for k, v in tasks_db.items()},
            'next_id': next_task_id
        }
        with open(DATA_FILE, 'w') as f:
            json.dump(data, f, indent=2)
    except Exception as e:
        print(f"Error saving tasks: {e}")

def get_current_time() -> str:
    """Get current timestamp as ISO string"""
    return datetime.now().isoformat()

# Load existing tasks on startup
load_tasks()

@mcp.tool()
def create_task(
    title: str,
    description: str = "",
    priority: str = "medium",
    tags: str = "",
    due_date: str = ""
) -> str:
    """Create a new task.
    
    Args:
        title: Task title (required)
        description: Detailed description of the task
        priority: Task priority (low, medium, high, urgent)
        tags: Comma-separated list of tags
        due_date: Due date in YYYY-MM-DD format
    """
    global next_task_id
    
    try:
        # Parse priority
        task_priority = Priority(priority.lower())
    except ValueError:
        return f"Invalid priority '{priority}'. Use: low, medium, high, urgent"
    
    # Parse tags
    task_tags = [tag.strip() for tag in tags.split(",") if tag.strip()]
    
    # Validate due date if provided
    task_due_date = None
    if due_date:
        try:
            datetime.fromisoformat(due_date)
            task_due_date = due_date
        except ValueError:
            return f"Invalid due date format. Use YYYY-MM-DD"
    
    # Create task
    current_time = get_current_time()
    task = Task(
        id=next_task_id,
        title=title,
        description=description,
        priority=task_priority,
        tags=task_tags,
        created_at=current_time,
        updated_at=current_time,
        due_date=task_due_date
    )
    
    tasks_db[next_task_id] = task
    next_task_id += 1
    save_tasks()
    
    return f"✅ Created task #{task.id}: {task.title}"

@mcp.tool()
def list_tasks(
    status: str = "all",
    priority: str = "all",
    tag: str = "",
    limit: int = 10
) -> str:
    """List tasks with optional filtering.
    
    Args:
        status: Filter by status (all, pending, in_progress, completed, cancelled)
        priority: Filter by priority (all, low, medium, high, urgent)
        tag: Filter by tag (exact match)
        limit: Maximum number of tasks to return
    """
    if not tasks_db:
        return "📝 No tasks found. Create your first task!"
    
    filtered_tasks = list(tasks_db.values())
    
    # Filter by status
    if status != "all":
        try:
            status_filter = TaskStatus(status)
            filtered_tasks = [t for t in filtered_tasks if t.status == status_filter]
        except ValueError:
            return f"Invalid status '{status}'. Use: all, pending, in_progress, completed, cancelled"
    
    # Filter by priority
    if priority != "all":
        try:
            priority_filter = Priority(priority)
            filtered_tasks = [t for t in filtered_tasks if t.priority == priority_filter]
        except ValueError:
            return f"Invalid priority '{priority}'. Use: all, low, medium, high, urgent"
    
    # Filter by tag
    if tag:
        filtered_tasks = [t for t in filtered_tasks if tag in t.tags]
    
    # Sort by creation date (newest first)
    filtered_tasks.sort(key=lambda x: x.created_at, reverse=True)
    
    # Apply limit
    filtered_tasks = filtered_tasks[:limit]
    
    if not filtered_tasks:
        return "📝 No tasks match your filters."
    
    # Format output
    result = f"📋 Found {len(filtered_tasks)} task(s):\n\n"
    
    for task in filtered_tasks:
        status_emoji = {
            TaskStatus.PENDING: "⏳",
            TaskStatus.IN_PROGRESS: "🔄",
            TaskStatus.COMPLETED: "✅",
            TaskStatus.CANCELLED: "❌"
        }
        
        priority_emoji = {
            Priority.LOW: "🟢",
            Priority.MEDIUM: "🟡",
            Priority.HIGH: "🟠",
            Priority.URGENT: "🔴"
        }
        
        tags_str = f" #{' #'.join(task.tags)}" if task.tags else ""
        due_str = f" (Due: {task.due_date})" if task.due_date else ""
        
        result += f"{status_emoji[task.status]} #{task.id} - {task.title}\n"
        result += f"   {priority_emoji[task.priority]} {task.priority.value.title()}{due_str}{tags_str}\n"
        if task.description:
            result += f"   📄 {task.description}\n"
        result += "\n"
    
    return result.strip()

@mcp.tool()
def get_task(task_id: int) -> str:
    """Get detailed information about a specific task.
    
    Args:
        task_id: The ID of the task to retrieve
    """
    if task_id not in tasks_db:
        return f"❌ Task #{task_id} not found."
    
    task = tasks_db[task_id]
    
    status_emoji = {
        TaskStatus.PENDING: "⏳",
        TaskStatus.IN_PROGRESS: "🔄",
        TaskStatus.COMPLETED: "✅",
        TaskStatus.CANCELLED: "❌"
    }
    
    priority_emoji = {
        Priority.LOW: "🟢",
        Priority.MEDIUM: "🟡",
        Priority.HIGH: "🟠",
        Priority.URGENT: "🔴"
    }
    
    result = f"📋 Task #{task.id}\n"
    result += f"Title: {task.title}\n"
    result += f"Status: {status_emoji[task.status]} {task.status.value.replace('_', ' ').title()}\n"
    result += f"Priority: {priority_emoji[task.priority]} {task.priority.value.title()}\n"
    
    if task.description:
        result += f"Description: {task.description}\n"
    
    if task.tags:
        result += f"Tags: #{' #'.join(task.tags)}\n"
    
    if task.due_date:
        result += f"Due Date: {task.due_date}\n"
    
    result += f"Created: {task.created_at}\n"
    result += f"Updated: {task.updated_at}\n"
    
    if task.completed_at:
        result += f"Completed: {task.completed_at}\n"
    
    return result

@mcp.tool()
def update_task(
    task_id: int,
    title: str = "",
    description: str = "",
    status: str = "",
    priority: str = "",
    tags: str = "",
    due_date: str = ""
) -> str:
    """Update an existing task. Only provided fields will be updated.
    
    Args:
        task_id: The ID of the task to update
        title: New task title
        description: New task description
        status: New status (pending, in_progress, completed, cancelled)
        priority: New priority (low, medium, high, urgent)
        tags: New comma-separated list of tags
        due_date: New due date in YYYY-MM-DD format (use 'none' to clear)
    """
    if task_id not in tasks_db:
        return f"❌ Task #{task_id} not found."
    
    task = tasks_db[task_id]
    updated_fields = []
    
    # Update title
    if title:
        task.title = title
        updated_fields.append("title")
    
    # Update description
    if description:
        task.description = description
        updated_fields.append("description")
    
    # Update status
    if status:
        try:
            new_status = TaskStatus(status)
            task.status = new_status
            updated_fields.append("status")
            
            # Set completion time if marking as completed
            if new_status == TaskStatus.COMPLETED and not task.completed_at:
                task.completed_at = get_current_time()
            elif new_status != TaskStatus.COMPLETED:
                task.completed_at = None
                
        except ValueError:
            return f"Invalid status '{status}'. Use: pending, in_progress, completed, cancelled"
    
    # Update priority
    if priority:
        try:
            task.priority = Priority(priority)
            updated_fields.append("priority")
        except ValueError:
            return f"Invalid priority '{priority}'. Use: low, medium, high, urgent"
    
    # Update tags
    if tags:
        if tags.lower() == "none":
            task.tags = []
        else:
            task.tags = [tag.strip() for tag in tags.split(",") if tag.strip()]
        updated_fields.append("tags")
    
    # Update due date
    if due_date:
        if due_date.lower() == "none":
            task.due_date = None
        else:
            try:
                datetime.fromisoformat(due_date)
                task.due_date = due_date
            except ValueError:
                return f"Invalid due date format. Use YYYY-MM-DD or 'none' to clear"
        updated_fields.append("due_date")
    
    if not updated_fields:
        return f"❌ No fields provided to update for task #{task_id}."
    
    # Update timestamp
    task.updated_at = get_current_time()
    save_tasks()
    
    return f"✅ Updated task #{task_id}: {', '.join(updated_fields)}"

@mcp.tool()
def delete_task(task_id: int) -> str:
    """Delete a task permanently.
    
    Args:
        task_id: The ID of the task to delete
    """
    if task_id not in tasks_db:
        return f"❌ Task #{task_id} not found."
    
    task = tasks_db[task_id]
    del tasks_db[task_id]
    save_tasks()
    
    return f"🗑️ Deleted task #{task_id}: {task.title}"

@mcp.tool()
def search_tasks(query: str, limit: int = 10) -> str:
    """Search tasks by title, description, or tags.
    
    Args:
        query: Search query (searches in title, description, and tags)
        limit: Maximum number of results to return
    """
    if not tasks_db:
        return "📝 No tasks to search."
    
    query_lower = query.lower()
    matching_tasks = []
    
    for task in tasks_db.values():
        # Search in title, description, and tags
        if (query_lower in task.title.lower() or 
            query_lower in task.description.lower() or
            any(query_lower in tag.lower() for tag in task.tags)):
            matching_tasks.append(task)
    
    if not matching_tasks:
        return f"🔍 No tasks found matching '{query}'."
    
    # Sort by relevance (title matches first, then description, then tags)
    def relevance_score(task):
        score = 0
        if query_lower in task.title.lower():
            score += 3
        if query_lower in task.description.lower():
            score += 2
        if any(query_lower in tag.lower() for tag in task.tags):
            score += 1
        return score
    
    matching_tasks.sort(key=relevance_score, reverse=True)
    matching_tasks = matching_tasks[:limit]
    
    result = f"🔍 Found {len(matching_tasks)} task(s) matching '{query}':\n\n"
    
    for task in matching_tasks:
        status_emoji = {
            TaskStatus.PENDING: "⏳",
            TaskStatus.IN_PROGRESS: "🔄",
            TaskStatus.COMPLETED: "✅",
            TaskStatus.CANCELLED: "❌"
        }
        
        result += f"{status_emoji[task.status]} #{task.id} - {task.title}\n"
        if task.description:
            result += f"   📄 {task.description[:100]}{'...' if len(task.description) > 100 else ''}\n"
        result += "\n"
    
    return result.strip()

@mcp.tool()
def get_stats() -> str:
    """Get task statistics and summary."""
    if not tasks_db:
        return "📊 No tasks yet. Create your first task to see statistics!"
    
    total_tasks = len(tasks_db)
    
    # Count by status
    status_counts = {}
    for status in TaskStatus:
        status_counts[status] = sum(1 for task in tasks_db.values() if task.status == status)
    
    # Count by priority
    priority_counts = {}
    for priority in Priority:
        priority_counts[priority] = sum(1 for task in tasks_db.values() if task.priority == priority)
    
    # Overdue tasks
    today = datetime.now().date()
    overdue_count = 0
    for task in tasks_db.values():
        if (task.due_date and task.status != TaskStatus.COMPLETED and 
            datetime.fromisoformat(task.due_date).date() < today):
            overdue_count += 1
    
    # Most common tags
    all_tags = []
    for task in tasks_db.values():
        all_tags.extend(task.tags)
    
    tag_counts = {}
    for tag in all_tags:
        tag_counts[tag] = tag_counts.get(tag, 0) + 1
    
    top_tags = sorted(tag_counts.items(), key=lambda x: x[1], reverse=True)[:5]
    
    result = f"📊 Task Statistics\n\n"
    result += f"Total Tasks: {total_tasks}\n\n"
    
    result += "📈 By Status:\n"
    for status, count in status_counts.items():
        emoji = {"pending": "⏳", "in_progress": "🔄", "completed": "✅", "cancelled": "❌"}
        result += f"  {emoji.get(status.value, '•')} {status.value.replace('_', ' ').title()}: {count}\n"
    
    result += "\n🎯 By Priority:\n"
    for priority, count in priority_counts.items():
        emoji = {"low": "🟢", "medium": "🟡", "high": "🟠", "urgent": "🔴"}
        result += f"  {emoji.get(priority.value, '•')} {priority.value.title()}: {count}\n"
    
    if overdue_count > 0:
        result += f"\n⚠️ Overdue Tasks: {overdue_count}\n"
    
    if top_tags:
        result += f"\n🏷️ Top Tags:\n"
        for tag, count in top_tags:
            result += f"  #{tag}: {count}\n"
    
    return result

def main():
    """Initialize and run the MCP server"""
    print("Starting Task Manager MCP Server...")
    print(f"Data file: {os.path.abspath(DATA_FILE)}")
    print(f"Loaded {len(tasks_db)} existing tasks")
    mcp.run(transport="stdio")

if __name__ == "__main__":
    main()