from __future__ import annotations

import logging
from collections import defaultdict
from dataclasses import dataclass
from typing import Dict, Optional, TYPE_CHECKING, Type

from dcs.unittype import UnitType, VehicleType

from game.theater import ControlPoint, SupplyRoute
from gen.ato import Package
from gen.flights.closestairfields import ObjectiveDistanceCache
from gen.flights.flight import Flight
from .db import PRICES
from .transfers import AirliftOrder, AirliftPlanner, RoadTransferOrder

if TYPE_CHECKING:
    from .game import Game


@dataclass(frozen=True)
class GroundUnitSource:
    control_point: ControlPoint
    requires_airlift: bool


class PendingUnitDeliveries:
    def __init__(self, destination: ControlPoint) -> None:
        self.destination = destination

        # Maps unit type to order quantity.
        self.units: Dict[Type[UnitType], int] = defaultdict(int)

    def __str__(self) -> str:
        return f"Pending delivery to {self.destination}"

    def order(self, units: Dict[Type[UnitType], int]) -> None:
        for k, v in units.items():
            self.units[k] += v

    def sell(self, units: Dict[Type[UnitType], int]) -> None:
        for k, v in units.items():
            self.units[k] -= v

    def refund_all(self, game: Game) -> None:
        self.refund(game, self.units)
        self.units = defaultdict(int)

    def refund(self, game: Game, units: Dict[Type[UnitType], int]) -> None:
        for unit_type, count in units.items():
            try:
                price = PRICES[unit_type]
            except KeyError:
                logging.error(f"Could not refund {unit_type.id}, price unknown")
                continue

            logging.info(f"Refunding {count} {unit_type.id} at {self.destination.name}")
            game.adjust_budget(price * count, player=self.destination.captured)

    def pending_orders(self, unit_type: Type[UnitType]) -> int:
        pending_units = self.units.get(unit_type)
        if pending_units is None:
            pending_units = 0
        return pending_units

    def available_next_turn(self, unit_type: Type[UnitType]) -> int:
        current_units = self.destination.base.total_units_of_type(unit_type)
        return self.pending_orders(unit_type) + current_units

    def process(self, game: Game) -> None:
        ground_unit_source = self.find_ground_unit_source(game)
        if ground_unit_source is None:
            game.message(
                f"{self.destination.name} lost its source for ground unit "
                "reinforcements. Refunding purchase price."
            )
            self.refund_all(game)
            return

        bought_units: Dict[Type[UnitType], int] = {}
        units_needing_transfer: Dict[Type[VehicleType], int] = {}
        sold_units: Dict[Type[UnitType], int] = {}
        for unit_type, count in self.units.items():
            coalition = "Ally" if self.destination.captured else "Enemy"
            name = unit_type.id

            if (
                issubclass(unit_type, VehicleType)
                and self.destination != ground_unit_source.control_point
            ):
                source = ground_unit_source.control_point
                d = units_needing_transfer
            else:
                source = self.destination
                d = bought_units

            if count >= 0:
                d[unit_type] = count
                game.message(
                    f"{coalition} reinforcements: {name} x {count} at {source}"
                )
            else:
                sold_units[unit_type] = -count
                game.message(f"{coalition} sold: {name} x {-count} at {source}")

        self.units = defaultdict(int)
        self.destination.base.commision_units(bought_units)
        self.destination.base.commit_losses(sold_units)

        if units_needing_transfer:
            ground_unit_source.control_point.base.commision_units(
                units_needing_transfer
            )
            if ground_unit_source.requires_airlift:
                self.create_air_transfer(
                    game, ground_unit_source.control_point, units_needing_transfer
                )
            else:
                self.create_road_transfer(
                    game, ground_unit_source.control_point, units_needing_transfer
                )

    def create_air_transfer(
        self, game: Game, source: ControlPoint, units: Dict[Type[VehicleType], int]
    ) -> None:
        planner = AirliftPlanner(game, source, self.destination, units)
        leftovers = planner.create_package_for_airlift()
        if leftovers:
            game.message(
                f"No airlift capacity remaining for {self.destination}. "
                "Remaining unit orders were refunded."
            )
            self.refund(game, leftovers)
            source.base.commit_losses(leftovers)

    def find_transport_for(
        self,
        origin: ControlPoint,
        destination: ControlPoint,
        units: Dict[Type[VehicleType], int],
    ) -> Optional[Flight]:
        pass

    def create_road_transfer(
        self, game: Game, source: ControlPoint, units: Dict[Type[VehicleType], int]
    ) -> None:
        game.transfers.new_transfer(
            RoadTransferOrder(
                source, self.destination, self.destination.captured, units
            )
        )

    def find_ground_unit_source(self, game: Game) -> Optional[GroundUnitSource]:
        # This is running *after* the turn counter has been incremented, so this is the
        # reaction to turn 0. On turn zero we allow units to be recruited anywhere for
        # delivery on turn 1 so that turn 1 always starts with units on the front line.
        if game.turn == 1:
            return GroundUnitSource(self.destination, requires_airlift=False)

        # Fast path if the destination is a valid source.
        if self.destination.can_recruit_ground_units(game):
            return GroundUnitSource(self.destination, requires_airlift=False)

        by_road = self.find_ground_unit_source_by_road(game)
        if by_road is not None:
            return GroundUnitSource(by_road, requires_airlift=False)

        by_air = self.find_ground_unit_source_by_air(game)
        if by_air is not None:
            return GroundUnitSource(by_air, requires_airlift=True)
        return None

    def find_ground_unit_source_by_road(self, game: Game) -> Optional[ControlPoint]:
        supply_route = SupplyRoute.for_control_point(self.destination)

        sources = []
        for control_point in supply_route:
            if control_point.can_recruit_ground_units(game):
                sources.append(control_point)

        if not sources:
            return None

        # Fast path to skip the distance calculation if we have only one option.
        if len(sources) == 1:
            return sources[0]

        closest = sources[0]
        distance = len(supply_route.shortest_path_between(self.destination, closest))
        for source in sources:
            new_distance = len(
                supply_route.shortest_path_between(self.destination, source)
            )
            if new_distance < distance:
                closest = source
                distance = new_distance
        return closest

    def find_ground_unit_source_by_air(self, game: Game) -> Optional[ControlPoint]:
        closest_airfields = ObjectiveDistanceCache.get_closest_airfields(
            self.destination
        )
        for airfield in closest_airfields.operational_airfields:
            if airfield.is_friendly(
                self.destination.captured
            ) and airfield.can_recruit_ground_units(game):
                return airfield
        return None