using Chessistics.Engine.Events;
using Chessistics.Engine.Model;

namespace Chessistics.Engine.Commands;

/// <summary>
/// Load a campaign: initializes the board with mission 0's terrain, stock, and unlocked pieces.
/// </summary>
public class LoadCampaignCommand : WorldCommand
{
    public override void AssertApplicationConditions(BoardState state)
    {
        if (state.Campaign == null)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(LoadCampaignCommand), "No campaign defined."));

        if (state.Campaign.CampaignDef.Missions.Count == 0)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(LoadCampaignCommand), "Campaign has no missions."));
    }

    protected override void DoApply(BoardState state, List<IWorldEvent> changeList)
    {
        var campaign = state.Campaign!;
        var mission = campaign.CurrentMission;

        // Apply terrain patch for mission 0
        state.ApplyTerrainPatch(mission.TerrainPatch, campaign.CurrentMissionIndex);

        // Add stock
        state.AddStock(mission.Stock);

        // Unlock pieces and levels
        foreach (var kind in mission.UnlockedPieces)
        {
            campaign.AvailablePieceKinds.Add(kind);
            changeList.Add(new PieceUnlockedEvent(kind, 1));
        }
        foreach (var upgrade in mission.UnlockedLevels)
        {
            campaign.AvailableLevels.Add(upgrade);
            changeList.Add(new PieceUnlockedEvent(upgrade.Kind, upgrade.Level));
        }

        state.Phase = SimPhase.Paused;

        changeList.Add(new CampaignLoadedEvent(campaign.CampaignDef.Name, 0));
        changeList.Add(new MissionStartedEvent(0, state.Width, state.Height));
    }
}

/// <summary>
/// Advance to the next mission: applies the terrain patch, adds stock, unlocks pieces.
/// </summary>
public class AdvanceMissionCommand : WorldCommand
{
    public override void AssertApplicationConditions(BoardState state)
    {
        if (state.Campaign == null)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(AdvanceMissionCommand), "No campaign defined."));

        if (state.Phase != SimPhase.MissionComplete)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(AdvanceMissionCommand), "Current mission is not complete."));

        if (state.Campaign.IsLastMission)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(AdvanceMissionCommand), "No more missions."));
    }

    protected override void DoApply(BoardState state, List<IWorldEvent> changeList)
    {
        var campaign = state.Campaign!;
        campaign.CurrentMissionIndex++;
        var mission = campaign.CurrentMission;

        // Apply terrain expansion
        var oldWidth = state.Width;
        var oldHeight = state.Height;
        state.ApplyTerrainPatch(mission.TerrainPatch, campaign.CurrentMissionIndex);

        if (state.Width != oldWidth || state.Height != oldHeight)
            changeList.Add(new TerrainExpandedEvent(state.Width, state.Height, mission.TerrainPatch.Cells));

        // Add stock
        state.AddStock(mission.Stock);

        // Unlock pieces and levels
        foreach (var kind in mission.UnlockedPieces)
        {
            campaign.AvailablePieceKinds.Add(kind);
            changeList.Add(new PieceUnlockedEvent(kind, 1));
        }
        foreach (var upgrade in mission.UnlockedLevels)
        {
            campaign.AvailableLevels.Add(upgrade);
            changeList.Add(new PieceUnlockedEvent(upgrade.Kind, upgrade.Level));
        }

        state.Phase = SimPhase.Paused;
        changeList.Add(new MissionStartedEvent(campaign.CurrentMissionIndex, state.Width, state.Height));
    }
}

/// <summary>
/// Move a piece already on the board (drag & drop). Validates the new placement.
/// </summary>
public class MovePieceCommand : WorldCommand
{
    public int PieceId { get; }
    public Coords NewStart { get; }
    public Coords NewEnd { get; }

    public MovePieceCommand(int pieceId, Coords newStart, Coords newEnd)
    {
        PieceId = pieceId;
        NewStart = newStart;
        NewEnd = newEnd;
    }

    public override void AssertApplicationConditions(BoardState state)
    {
        var piece = state.GetPieceById(PieceId);
        if (piece == null)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(MovePieceCommand), $"Piece {PieceId} not found."));

        if (!state.IsOnBoard(NewStart) || !state.IsOnBoard(NewEnd))
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(MovePieceCommand), "Position is off the board."));

        if (state.GetCell(NewStart) == CellType.Wall)
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(MovePieceCommand), "Cannot place on a wall."));

        if (!Rules.MoveValidator.IsLegalPlacement(piece.Kind, NewStart, NewEnd, state))
            throw new CommandRejectedException(
                new CommandRejectedEvent(nameof(MovePieceCommand), "Illegal move for this piece type."));
    }

    protected override void DoApply(BoardState state, List<IWorldEvent> changeList)
    {
        var piece = state.GetPieceById(PieceId)!;
        var oldStart = piece.StartCell;
        var oldEnd = piece.EndCell;

        piece.SetPosition(NewStart, NewEnd);
        piece.Cargo = null;

        state.OccupiedCells.Add(NewStart);
        state.OccupiedCells.Add(NewEnd);

        changeList.Add(new PieceMovedByPlayerEvent(PieceId, oldStart, oldEnd, NewStart, NewEnd));
    }
}