import {
  clampNpcTokenSessionScale,
  DEFAULT_NPC_TOKEN_SESSION_SCALE,
  type SceneNpcTokensSessionEvent,
  type SceneNpcTokensSessionPlacement,
  type SceneNpcTokensSessionState,
} from '../../shared/types/appPlayers';
import { normalizeNpcDisposition } from '../../shared/types/npcDisposition';
import { rotateMapNormPointByCwSteps } from '../../shared/types/scenePreviewRotation';

function emptyState(revision = 1): SceneNpcTokensSessionState {
  return {
    revision,
    byPlacementId: {},
    scale: DEFAULT_NPC_TOKEN_SESSION_SCALE,
  };
}

function isEmptyPlacement(p: SceneNpcTokensSessionPlacement): boolean {
  return p.nx === undefined && p.ny === undefined && !p.disposition && !p.inactive;
}

function withMove(
  prev: SceneNpcTokensSessionPlacement | undefined,
  nx: number,
  ny: number,
): SceneNpcTokensSessionPlacement {
  return {
    nx,
    ny,
    ...(prev?.disposition ? { disposition: prev.disposition } : {}),
    ...(prev?.inactive ? { inactive: true } : {}),
  };
}

function withoutPlacement(
  state: SceneNpcTokensSessionState,
  placementId: string,
): SceneNpcTokensSessionState {
  if (!(placementId in state.byPlacementId)) return state;
  const { [placementId]: _removed, ...rest } = state.byPlacementId;
  return {
    revision: state.revision + 1,
    byPlacementId: rest,
    scale: state.scale,
  };
}

export class SceneNpcTokensSessionStore {
  private state: SceneNpcTokensSessionState = emptyState();

  getState(): SceneNpcTokensSessionState {
    return this.state;
  }

  reset(): SceneNpcTokensSessionState {
    if (
      Object.keys(this.state.byPlacementId).length === 0 &&
      this.state.scale === DEFAULT_NPC_TOKEN_SESSION_SCALE
    ) {
      return this.state;
    }
    this.state = emptyState(this.state.revision + 1);
    return this.state;
  }

  /** Rotate session position overrides with the scene preview (CSS rotate steps). */
  rotateMapCwSteps(steps: number): SceneNpcTokensSessionState {
    const n = ((steps % 4) + 4) % 4;
    if (n === 0) return this.state;
    const ids = Object.keys(this.state.byPlacementId);
    if (ids.length === 0) return this.state;
    let changed = false;
    const byPlacementId: SceneNpcTokensSessionState['byPlacementId'] = {};
    for (const id of ids) {
      const prev = this.state.byPlacementId[id];
      if (!prev) continue;
      if (typeof prev.nx === 'number' && typeof prev.ny === 'number') {
        const p = rotateMapNormPointByCwSteps(prev.nx, prev.ny, n);
        byPlacementId[id] = { ...prev, nx: p.nx, ny: p.ny };
        changed = true;
      } else {
        byPlacementId[id] = prev;
      }
    }
    if (!changed) return this.state;
    this.state = {
      revision: this.state.revision + 1,
      byPlacementId,
      scale: this.state.scale,
    };
    return this.state;
  }

  dispatch(event: SceneNpcTokensSessionEvent): SceneNpcTokensSessionState {
    switch (event.kind) {
      case 'clear':
        return this.reset();
      case 'setScale': {
        const scale = clampNpcTokenSessionScale(event.scale);
        if (this.state.scale === scale) return this.state;
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          scale,
        };
        return this.state;
      }
      case 'move': {
        const placementId = String(event.placementId ?? '');
        if (!placementId) return this.state;
        const nx = Math.max(0, Math.min(1, event.nx));
        const ny = Math.max(0, Math.min(1, event.ny));
        if (!Number.isFinite(nx) || !Number.isFinite(ny)) return this.state;
        const prev = this.state.byPlacementId[placementId];
        if (prev && prev.nx === nx && prev.ny === ny) return this.state;
        this.state = {
          revision: this.state.revision + 1,
          byPlacementId: {
            ...this.state.byPlacementId,
            [placementId]: withMove(prev, nx, ny),
          },
          scale: this.state.scale,
        };
        return this.state;
      }
      case 'setDisposition': {
        const placementId = String(event.placementId ?? '');
        if (!placementId) return this.state;
        const disposition = normalizeNpcDisposition(event.disposition);
        const prev = this.state.byPlacementId[placementId];
        if (prev?.disposition === disposition) return this.state;
        const next: SceneNpcTokensSessionPlacement = {
          ...(prev?.nx !== undefined ? { nx: prev.nx } : {}),
          ...(prev?.ny !== undefined ? { ny: prev.ny } : {}),
          disposition,
          ...(prev?.inactive ? { inactive: true } : {}),
        };
        this.state = {
          revision: this.state.revision + 1,
          byPlacementId: {
            ...this.state.byPlacementId,
            [placementId]: next,
          },
          scale: this.state.scale,
        };
        return this.state;
      }
      case 'setInactive': {
        const placementId = String(event.placementId ?? '');
        if (!placementId) return this.state;
        const inactive = Boolean(event.inactive);
        const prev = this.state.byPlacementId[placementId];
        if (Boolean(prev?.inactive) === inactive) return this.state;
        const next: SceneNpcTokensSessionPlacement = {
          ...(prev?.nx !== undefined ? { nx: prev.nx } : {}),
          ...(prev?.ny !== undefined ? { ny: prev.ny } : {}),
          ...(prev?.disposition ? { disposition: prev.disposition } : {}),
          ...(inactive ? { inactive: true } : {}),
        };
        if (isEmptyPlacement(next)) {
          this.state = withoutPlacement(this.state, placementId);
          return this.state;
        }
        this.state = {
          revision: this.state.revision + 1,
          byPlacementId: {
            ...this.state.byPlacementId,
            [placementId]: next,
          },
          scale: this.state.scale,
        };
        return this.state;
      }
      default: {
        const _exhaustive: never = event;
        void _exhaustive;
        return this.state;
      }
    }
  }
}