from datetime import datetime, timedelta
from enum import Enum
import json
from typing import Sequence

from zoneinfo import ZoneInfo
from tzlocal import get_localzone_name  # ← returns "Europe/Paris", etc.

from mcp.server import Server
from mcp.server.stdio import stdio_server
from mcp.types import Tool, TextContent, ImageContent, EmbeddedResource, ErrorData, INVALID_PARAMS
from mcp.shared.exceptions import McpError

from pydantic import BaseModel


class TimeTools(str, Enum):
    GET_CURRENT_TIME = "get_current_time"
    CONVERT_TIME = "convert_time"


class TimeResult(BaseModel):
    timezone: str
    datetime: str
    day_of_week: str
    is_dst: bool


class TimeConversionResult(BaseModel):
    source: TimeResult
    target: TimeResult
    time_difference: str


class TimeConversionInput(BaseModel):
    source_tz: str
    time: str
    target_tz_list: list[str]


def get_local_tz(local_tz_override: str | None = None) -> ZoneInfo:
    if local_tz_override:
        return ZoneInfo(local_tz_override)

    # Get local timezone from datetime.now()
    local_tzname = get_localzone_name()
    if local_tzname is not None:
        return ZoneInfo(local_tzname)
    # Default to UTC if local timezone cannot be determined
    return ZoneInfo("UTC")


def get_zoneinfo(timezone_name: str) -> ZoneInfo:
    try:
        return ZoneInfo(timezone_name)
    except Exception as e:
        raise McpError(ErrorData(code=INVALID_PARAMS, message=f"Invalid timezone: {str(e)}"))


class TimeServer:
    def get_current_time(self, timezone_name: str) -> TimeResult:
        """Get current time in specified timezone"""
        timezone = get_zoneinfo(timezone_name)
        current_time = datetime.now(timezone)

        return TimeResult(
            timezone=timezone_name,
            datetime=current_time.isoformat(timespec="seconds"),
            day_of_week=current_time.strftime("%A"),
            is_dst=bool(current_time.dst()),
        )

    def convert_time(
        self, source_tz: str, time_str: str, target_tz: str
    ) -> TimeConversionResult:
        """Convert time between timezones"""
        source_timezone = get_zoneinfo(source_tz)
        target_timezone = get_zoneinfo(target_tz)

        try:
            parsed_time = datetime.strptime(time_str, "%H:%M").time()
        except ValueError:
            raise ValueError("Invalid time format. Expected HH:MM [24-hour format]")

        now = datetime.now(source_timezone)
        source_time = datetime(
            now.year,
            now.month,
            now.day,
            parsed_time.hour,
            parsed_time.minute,
            tzinfo=source_timezone,
        )

        target_time = source_time.astimezone(target_timezone)
        source_offset = source_time.utcoffset() or timedelta()
        target_offset = target_time.utcoffset() or timedelta()
        hours_difference = (target_offset - source_offset).total_seconds() / 3600

        if hours_difference.is_integer():
            time_diff_str = f"{hours_difference:+.1f}h"
        else:
            # For fractional hours like Nepal's UTC+5:45
            time_diff_str = f"{hours_difference:+.2f}".rstrip("0").rstrip(".") + "h"

        return TimeConversionResult(
            source=TimeResult(
                timezone=source_tz,
                datetime=source_time.isoformat(timespec="seconds"),
                day_of_week=source_time.strftime("%A"),
                is_dst=bool(source_time.dst()),
            ),
            target=TimeResult(
                timezone=target_tz,
                datetime=target_time.isoformat(timespec="seconds"),
                day_of_week=target_time.strftime("%A"),
                is_dst=bool(target_time.dst()),
            ),
            time_difference=time_diff_str,
        )


async def serve(local_timezone: str | None = None) -> None:
    server = Server("mcp-time")
    time_server = TimeServer()
    local_tz = str(get_local_tz(local_timezone))

    @server.list_tools()
    async def list_tools() -> list[Tool]:
        """List available time tools."""
        return [
            Tool(
                name=TimeTools.GET_CURRENT_TIME.value,
                description="Get current time in a specific timezones",
                inputSchema={
                    "type": "object",
                    "properties": {
                        "timezone": {
                            "type": "string",
                            "description": f"IANA timezone name (e.g., 'America/New_York', 'Europe/London'). Use '{local_tz}' as local timezone if no timezone provided by the user.",
                        }
                    },
                    "required": ["timezone"],
                },
            ),
            Tool(
                name=TimeTools.CONVERT_TIME.value,
                description="Convert time between timezones",
                inputSchema={
                    "type": "object",
                    "properties": {
                        "source_timezone": {
                            "type": "string",
                            "description": f"Source IANA timezone name (e.g., 'America/New_York', 'Europe/London'). Use '{local_tz}' as local timezone if no source timezone provided by the user.",
                        },
                        "time": {
                            "type": "string",
                            "description": "Time to convert in 24-hour format (HH:MM)",
                        },
                        "target_timezone": {
                            "type": "string",
                            "description": f"Target IANA timezone name (e.g., 'Asia/Tokyo', 'America/San_Francisco'). Use '{local_tz}' as local timezone if no target timezone provided by the user.",
                        },
                    },
                    "required": ["source_timezone", "time", "target_timezone"],
                },
            ),
        ]

    @server.call_tool()
    async def call_tool(
        name: str, arguments: dict
    ) -> Sequence[TextContent | ImageContent | EmbeddedResource]:
        """Handle tool calls for time queries."""
        try:
            match name:
                case TimeTools.GET_CURRENT_TIME.value:
                    timezone = arguments.get("timezone")
                    if not timezone:
                        raise ValueError("Missing required argument: timezone")

                    result = time_server.get_current_time(timezone)

                case TimeTools.CONVERT_TIME.value:
                    if not all(
                        k in arguments
                        for k in ["source_timezone", "time", "target_timezone"]
                    ):
                        raise ValueError("Missing required arguments")

                    result = time_server.convert_time(
                        arguments["source_timezone"],
                        arguments["time"],
                        arguments["target_timezone"],
                    )
                case _:
                    raise ValueError(f"Unknown tool: {name}")

            return [
                TextContent(type="text", text=json.dumps(result.model_dump(), indent=2))
            ]

        except Exception as e:
            raise ValueError(f"Error processing mcp-server-time query: {str(e)}")

    options = server.create_initialization_options()
    async with stdio_server() as (read_stream, write_stream):
        await server.run(read_stream, write_stream, options)
