"""
DungeonMaster AI - MCP Fallback Handlers

Provides fallback functionality when MCP server is unavailable.
Local dice rolling ensures basic gameplay can continue.
"""

from __future__ import annotations

import logging
import random
import re
from datetime import datetime

logger = logging.getLogger(__name__)


class FallbackHandler:
    """
    Provides fallback functionality when MCP server is unavailable.

    Currently supports:
    - Basic dice rolling (roll, roll_check)

    Future fallbacks could include:
    - Cached monster/spell data
    - Basic character stat lookups
    """

    # Tools that have fallback implementations
    SUPPORTED_TOOLS: set[str] = {"roll", "roll_check", "mcp_roll", "mcp_roll_check"}

    # Regex for parsing dice notation
    # Matches: 2d6, 1d20+5, 4d6-2, d8, 2d10+3
    DICE_PATTERN = re.compile(
        r"^(\d*)d(\d+)([+-]\d+)?$",
        re.IGNORECASE,
    )

    # Advanced dice notation (keep highest/lowest)
    # Matches: 4d6kh3, 2d20kl1
    ADVANCED_DICE_PATTERN = re.compile(
        r"^(\d+)d(\d+)(k[hl])(\d+)?([+-]\d+)?$",
        re.IGNORECASE,
    )

    def can_handle(self, tool_name: str) -> bool:
        """Check if a fallback exists for this tool."""
        return tool_name in self.SUPPORTED_TOOLS

    def get_unavailable_message(self) -> str:
        """User-friendly message about limited functionality."""
        return (
            "The game server is temporarily unavailable. "
            "Some features like rules lookup and character management are limited, "
            "but basic dice rolling still works."
        )

    async def handle_roll(
        self,
        notation: str,
        reason: str | None = None,
        secret: bool = False,
    ) -> dict[str, object]:
        """
        Local dice rolling fallback.

        Supports:
        - Basic: 2d6, 1d20+5, d8
        - Keep highest: 4d6kh3 (roll 4d6, keep highest 3)
        - Keep lowest: 2d20kl1 (disadvantage)

        Args:
            notation: Dice notation string
            reason: Optional reason for the roll
            secret: Whether this is a secret roll (not shown to players)

        Returns:
            Result dict compatible with MCP roll tool format
        """
        notation = notation.strip().lower()
        timestamp = datetime.now().isoformat()

        # Try advanced notation first (keep highest/lowest)
        advanced_match = self.ADVANCED_DICE_PATTERN.match(notation)
        if advanced_match:
            return self._roll_advanced(
                advanced_match,
                notation,
                reason,
                secret,
                timestamp,
            )

        # Try basic notation
        basic_match = self.DICE_PATTERN.match(notation)
        if basic_match:
            return self._roll_basic(
                basic_match,
                notation,
                reason,
                secret,
                timestamp,
            )

        # Invalid notation
        logger.warning(f"Invalid dice notation in fallback: {notation}")
        return {
            "success": False,
            "error": f"Invalid dice notation: {notation}",
            "degraded_mode": True,
        }

    def _roll_basic(
        self,
        match: re.Match[str],
        notation: str,
        reason: str | None,
        secret: bool,
        timestamp: str,
    ) -> dict[str, object]:
        """Handle basic dice notation like 2d6+3."""
        num_dice = int(match.group(1)) if match.group(1) else 1
        die_size = int(match.group(2))
        modifier = int(match.group(3)) if match.group(3) else 0

        # Sanity checks
        if num_dice < 1 or num_dice > 100:
            return {
                "success": False,
                "error": f"Invalid number of dice: {num_dice} (must be 1-100)",
                "degraded_mode": True,
            }
        if die_size < 2 or die_size > 100:
            return {
                "success": False,
                "error": f"Invalid die size: d{die_size} (must be d2-d100)",
                "degraded_mode": True,
            }

        # Roll the dice
        rolls = [random.randint(1, die_size) for _ in range(num_dice)]
        total = sum(rolls) + modifier

        # Build breakdown string
        if modifier > 0:
            breakdown = f"[{', '.join(map(str, rolls))}] + {modifier}"
        elif modifier < 0:
            breakdown = f"[{', '.join(map(str, rolls))}] - {abs(modifier)}"
        else:
            breakdown = f"[{', '.join(map(str, rolls))}]"

        return {
            "success": True,
            "notation": notation,
            "total": total,
            "rolls": rolls,
            "dice": rolls,  # Alias for compatibility
            "individual_rolls": rolls,  # Another alias
            "modifier": modifier,
            "breakdown": breakdown,
            "formatted": f"{notation} = {breakdown} = {total}",
            "reason": reason or "",
            "secret": secret,
            "timestamp": timestamp,
            "degraded_mode": True,
        }

    def _roll_advanced(
        self,
        match: re.Match[str],
        notation: str,
        reason: str | None,
        secret: bool,
        timestamp: str,
    ) -> dict[str, object]:
        """Handle advanced dice notation like 4d6kh3."""
        num_dice = int(match.group(1))
        die_size = int(match.group(2))
        keep_type = match.group(3).lower()  # kh or kl
        keep_count = int(match.group(4)) if match.group(4) else 1
        modifier = int(match.group(5)) if match.group(5) else 0

        # Sanity checks
        if num_dice < 1 or num_dice > 100:
            return {
                "success": False,
                "error": f"Invalid number of dice: {num_dice}",
                "degraded_mode": True,
            }
        if keep_count > num_dice:
            return {
                "success": False,
                "error": f"Cannot keep {keep_count} dice from {num_dice} rolled",
                "degraded_mode": True,
            }

        # Roll all dice
        rolls = [random.randint(1, die_size) for _ in range(num_dice)]

        # Keep highest or lowest
        sorted_rolls = sorted(rolls, reverse=(keep_type == "kh"))
        kept_rolls = sorted_rolls[:keep_count]
        dropped_rolls = sorted_rolls[keep_count:]

        total = sum(kept_rolls) + modifier

        # Build breakdown string
        kept_str = f"[{', '.join(map(str, kept_rolls))}]"
        dropped_str = f" (dropped: {', '.join(map(str, dropped_rolls))})" if dropped_rolls else ""

        if modifier > 0:
            breakdown = f"{kept_str}{dropped_str} + {modifier}"
        elif modifier < 0:
            breakdown = f"{kept_str}{dropped_str} - {abs(modifier)}"
        else:
            breakdown = f"{kept_str}{dropped_str}"

        return {
            "success": True,
            "notation": notation,
            "total": total,
            "rolls": rolls,
            "dice": rolls,
            "individual_rolls": rolls,
            "kept_rolls": kept_rolls,
            "dropped_rolls": dropped_rolls,
            "modifier": modifier,
            "breakdown": breakdown,
            "formatted": f"{notation} = {breakdown} = {total}",
            "reason": reason or "",
            "secret": secret,
            "timestamp": timestamp,
            "degraded_mode": True,
        }

    async def handle_roll_check(
        self,
        modifier: int = 0,
        dc: int | None = None,
        advantage: bool = False,
        disadvantage: bool = False,
        skill_name: str | None = None,
    ) -> dict[str, object]:
        """
        Local ability check/save fallback.

        Rolls 1d20 with modifier, handles advantage/disadvantage.

        Args:
            modifier: Modifier to add to the roll
            dc: Difficulty class to check against
            advantage: Roll with advantage (2d20 keep highest)
            disadvantage: Roll with disadvantage (2d20 keep lowest)
            skill_name: Name of skill/ability for logging

        Returns:
            Result dict compatible with MCP roll_check format
        """
        timestamp = datetime.now().isoformat()

        # Roll d20(s)
        if advantage and not disadvantage:
            rolls = [random.randint(1, 20), random.randint(1, 20)]
            d20_result = max(rolls)
            roll_type = "advantage"
        elif disadvantage and not advantage:
            rolls = [random.randint(1, 20), random.randint(1, 20)]
            d20_result = min(rolls)
            roll_type = "disadvantage"
        else:
            rolls = [random.randint(1, 20)]
            d20_result = rolls[0]
            roll_type = "normal"

        total = d20_result + modifier

        # Check success/failure
        success = None
        result_str = ""
        if dc is not None:
            success = total >= dc
            result_str = "SUCCESS" if success else "FAILURE"

        # Build breakdown
        if len(rolls) > 1:
            rolls_str = f"[{rolls[0]}, {rolls[1]}] → {d20_result}"
        else:
            rolls_str = str(d20_result)

        if modifier >= 0:
            breakdown = f"{rolls_str} + {modifier}"
        else:
            breakdown = f"{rolls_str} - {abs(modifier)}"

        # Build formatted string
        skill_part = f" ({skill_name})" if skill_name else ""
        dc_part = f" vs DC {dc}" if dc is not None else ""
        result_part = f" - {result_str}" if result_str else ""
        formatted = f"d20{skill_part} = {breakdown} = {total}{dc_part}{result_part}"

        return {
            "success": True,
            "total": total,
            "d20_result": d20_result,
            "rolls": rolls,
            "modifier": modifier,
            "dc": dc,
            "check_success": success,
            "result": result_str.lower() if result_str else None,
            "roll_type": roll_type,
            "is_critical": d20_result == 20,
            "is_fumble": d20_result == 1,
            "skill_name": skill_name,
            "breakdown": breakdown,
            "formatted": formatted,
            "timestamp": timestamp,
            "degraded_mode": True,
        }

    async def handle(
        self,
        tool_name: str,
        arguments: dict[str, object],
    ) -> dict[str, object]:
        """
        Route a tool call to the appropriate fallback handler.

        Args:
            tool_name: Name of the tool
            arguments: Tool arguments

        Returns:
            Fallback result or error dict
        """
        # Normalize tool name (remove mcp_ prefix if present)
        normalized_name = tool_name.replace("mcp_", "")

        if normalized_name == "roll":
            reason_val = arguments.get("reason")
            return await self.handle_roll(
                notation=str(arguments.get("notation", "1d20")),
                reason=str(reason_val) if reason_val else None,
                secret=bool(arguments.get("secret", False)),
            )
        elif normalized_name == "roll_check":
            dc_val = arguments.get("dc")
            return await self.handle_roll_check(
                modifier=int(str(arguments.get("modifier", 0))),
                dc=int(str(dc_val)) if dc_val is not None else None,
                advantage=bool(arguments.get("advantage", False)),
                disadvantage=bool(arguments.get("disadvantage", False)),
                skill_name=str(arguments.get("skill_name")) if arguments.get("skill_name") else None,
            )
        else:
            return {
                "success": False,
                "error": f"No fallback available for tool: {tool_name}",
                "degraded_mode": True,
            }