import { StopId } from '../stops/stops.js';
import { durationToString, timeToString } from '../timetable/time.js';
import { routeTypeToString } from '../timetable/timetable.js';
import { Result } from './result.js';
import {
  AccessEdge,
  RoutingEdge,
  TransferEdge,
  VehicleEdge,
} from './router.js';

/**
 * Configuration for DOT graph styling.
 */
const DOT_CONFIG = {
  colors: {
    rounds: [
      '#60a5fa', // Round 1 - Blue
      '#ff9800', // Round 2 - Orange
      '#14b8a6', // Round 3 - Teal
      '#fb7185', // Round 4 - Pink
      '#ffdf00', // Round 5 - Yellow
      '#b600ff', // Round 6 - Purple
      '#ee82ee', // Round 7+ - Violet
    ],
    defaultRound: '#888888',
    originStation: '#60a5fa',
    destinationStation: '#ee82ee',
    defaultStation: 'white',
    continuationFill: '#ffffcc',
  },
  penWidth: {
    default: 1,
    continuation: 2,
    continuationEdge: 3,
  },
} as const;

/**
 * Type guard to check if an edge is a VehicleEdge.
 */
function isVehicleEdge(edge: RoutingEdge): edge is VehicleEdge {
  return 'routeId' in edge && 'stopIndex' in edge && 'hopOffStopIndex' in edge;
}

/**
 * Type guard to check if an edge is a TransferEdge.
 */
function isTransferEdge(edge: RoutingEdge): edge is TransferEdge {
  return 'from' in edge && 'to' in edge && 'type' in edge;
}

/**
 * Type guard to check if an edge is an AccessEdge (walking access leg).
 */
function isAccessEdge(edge: RoutingEdge): edge is AccessEdge {
  return 'from' in edge && 'duration' in edge;
}

/**
 * Helper class for building DOT graph syntax.
 */
class DotBuilder {
  private lines: string[] = [];

  /**
   * Adds the DOT graph header with default styling.
   */
  addHeader(): this {
    this.lines.push(
      'digraph RoutingGraph {',
      '  graph [overlap=false, splines=true, rankdir=TB, bgcolor=white, nodesep=0.8, ranksep=1.2, concentrate=true];',
      '  node [fontname="Arial" margin=0.1];',
      '  edge [fontname="Arial" fontsize=10];',
    );
    return this;
  }

  /**
   * Adds a comment section to the graph.
   */
  addComment(comment: string): this {
    this.lines.push('', `  // ${comment}`);
    return this;
  }

  /**
   * Adds a node with the given attributes.
   */
  addNode(id: string, attrs: Record<string, string>): this {
    const attrStr = Object.entries(attrs)
      .map(([k, v]) => `${k}="${v}"`)
      .join(' ');
    this.lines.push(`  "${id}" [${attrStr}];`);
    return this;
  }

  /**
   * Adds an edge between two nodes with optional attributes.
   */
  addEdge(from: string, to: string, attrs: Record<string, string> = {}): this {
    const attrStr = Object.entries(attrs)
      .map(([k, v]) => `${k}="${v}"`)
      .join(' ');
    const attrPart = attrStr ? ` [${attrStr}]` : '';
    this.lines.push(`  "${from}" -> "${to}"${attrPart};`);
    return this;
  }

  /**
   * Adds raw lines to the graph.
   */
  addRaw(lines: string[]): this {
    this.lines.push(...lines);
    return this;
  }

  /**
   * Builds the final DOT graph string.
   */
  build(): string {
    this.lines.push('}');
    return this.lines.join('\n');
  }
}

/**
 * Generates DOT graph visualizations of routing results.
 *
 * The generated graph shows:
 * - Stations as rectangular nodes (origin=blue, destination=violet)
 * - Vehicle edges as ovals with route info
 * - Transfer edges as dashed ovals
 * - Continuation edges (same-station transfers) as bold yellow ovals
 *
 * @example
 * ```typescript
 * const plotter = new Plotter(routingResult);
 * const dotGraph = plotter.plotDotGraph();
 * // Use with Graphviz: dot -Tpng -o graph.png
 * ```
 */
export class Plotter {
  private result: Result;

  constructor(result: Result) {
    this.result = result;
  }

  /**
   * Generates a unique node ID for a station.
   */
  private stationNodeId(stopId: StopId): string {
    return `s_${stopId}`;
  }

  /**
   * Generates a unique node ID for a vehicle edge oval.
   */
  private vehicleEdgeNodeId(
    fromStopId: StopId,
    toStopId: StopId,
    routeId: number,
    round: number,
  ): string {
    return `e_${fromStopId}_${toStopId}_${routeId}_${round}`;
  }

  /**
   * Generates a unique node ID for a transfer edge oval.
   */
  private transferEdgeNodeId(
    fromStopId: StopId,
    toStopId: StopId,
    round: number,
  ): string {
    return `e_${fromStopId}_${toStopId}_${round}`;
  }

  /**
   * Generates a unique node ID for a walking access edge oval.
   */
  private accessEdgeNodeId(fromStopId: StopId, toStopId: StopId): string {
    return `access_${fromStopId}_${toStopId}`;
  }

  /**
   * Generates a unique node ID for a continuation edge oval.
   */
  private continuationNodeId(
    fromStopId: StopId,
    toStopId: StopId,
    round: number,
  ): string {
    return `continuation_${fromStopId}_${toStopId}_${round}`;
  }

  /**
   * Gets the color for a round based on the configured palette.
   */
  private getRoundColor(round: number): string {
    if (round === 0) {
      return DOT_CONFIG.colors.defaultRound;
    }

    const colorIndex = Math.min(round - 1, DOT_CONFIG.colors.rounds.length - 1);
    return DOT_CONFIG.colors.rounds[colorIndex] ?? '#ee82ee';
  }

  /**
   * Gets the appropriate fill color for a station based on its type.
   */
  private getStationFillColor(
    isOrigin: boolean,
    isDestination: boolean,
  ): string {
    if (isOrigin) {
      return DOT_CONFIG.colors.originStation;
    }
    if (isDestination) {
      return DOT_CONFIG.colors.destinationStation;
    }
    return DOT_CONFIG.colors.defaultStation;
  }

  /**
   * Escapes special characters in DOT strings to prevent syntax errors.
   */
  private escapeDotString(str: string): string {
    return str
      .replace(/\\/g, '\\\\')
      .replace(/"/g, '\\"')
      .replace(/\n/g, '\\n')
      .replace(/\r/g, '\\r')
      .replace(/\t/g, '\\t');
  }

  /**
   * Formats a stop name for display, including platform information.
   */
  private formatStopName(stopId: StopId): string {
    const stop = this.result.stopsIndex.findStopById(stopId);
    if (!stop) {
      return `Unknown Stop (${stopId})`;
    }

    const escapedName = this.escapeDotString(stop.name);
    const escapedPlatform = stop.platform
      ? this.escapeDotString(stop.platform)
      : '';

    return escapedPlatform
      ? `${escapedName}\\nPl. ${escapedPlatform}`
      : escapedName;
  }

  /**
   * Determines station type (origin/destination) information.
   */
  private getStationInfo(stopId: StopId): {
    isOrigin: boolean;
    isDestination: boolean;
  } {
    const isOrigin = this.result.routingState.graph[0]?.[stopId] !== undefined;
    const isDestination =
      this.result.routingState.destinations.includes(stopId);
    return { isOrigin, isDestination };
  }

  /**
   * Resolves the actual StopId from a VehicleEdge's stopIndex.
   */
  private getVehicleEdgeFromStopId(edge: VehicleEdge): StopId | undefined {
    const route = this.result.timetable.getRoute(edge.routeId);
    return route?.stopId(edge.stopIndex);
  }

  /**
   * Resolves the actual StopId from a VehicleEdge's hopOffStopIndex.
   */
  private getVehicleEdgeToStopId(edge: VehicleEdge): StopId | undefined {
    const route = this.result.timetable.getRoute(edge.routeId);
    return route?.stopId(edge.hopOffStopIndex);
  }

  /**
   * Creates a DOT node for a station.
   */
  private createStationNode(stopId: StopId): string | null {
    const stop = this.result.stopsIndex.findStopById(stopId);
    if (!stop) {
      return null;
    }

    const displayName = this.formatStopName(stopId);
    const stopIdStr = this.escapeDotString(String(stopId));
    const nodeId = this.stationNodeId(stopId);
    const stationInfo = this.getStationInfo(stopId);
    const fillColor = this.getStationFillColor(
      stationInfo.isOrigin,
      stationInfo.isDestination,
    );

    return `  "${nodeId}" [label="${displayName}\\n${stopIdStr}" shape=box style=filled fillcolor="${fillColor}"];`;
  }

  /**
   * Creates a vehicle edge with route information oval in the middle.
   */
  private createVehicleEdge(edge: VehicleEdge, round: number): string[] {
    const route = this.result.timetable.getRoute(edge.routeId);
    if (!route) {
      return [];
    }

    const fromStopId = route.stopId(edge.stopIndex);
    const toStopId = route.stopId(edge.hopOffStopIndex);
    const fromNodeId = this.stationNodeId(fromStopId);
    const toNodeId = this.stationNodeId(toStopId);
    const roundColor = this.getRoundColor(round);
    const routeOvalId = this.vehicleEdgeNodeId(
      fromStopId,
      toStopId,
      edge.routeId,
      round,
    );

    const serviceRouteInfo = this.result.timetable.getServiceRouteInfo(route);
    const routeName = serviceRouteInfo.name;
    const routeType = routeTypeToString(serviceRouteInfo.type);

    const departureTime = timeToString(
      route.departureFrom(edge.stopIndex, edge.tripIndex),
    );
    const arrivalTime = timeToString(edge.arrival);

    const escapedRouteName = this.escapeDotString(routeName);
    const escapedRouteType = this.escapeDotString(routeType);
    const routeInfo = `${edge.routeId}:${edge.tripIndex}`;
    const ovalLabel = `${escapedRouteType} ${escapedRouteName}\\n${routeInfo}\\n${departureTime} → ${arrivalTime}`;

    return [
      `  "${routeOvalId}" [label="${ovalLabel}" shape=oval style=filled fillcolor="white" color="${roundColor}"];`,
      `  "${fromNodeId}" -> "${routeOvalId}" [color="${roundColor}"];`,
      `  "${routeOvalId}" -> "${toNodeId}" [color="${roundColor}"];`,
    ];
  }

  /**
   * Creates a walking access leg as a dashed oval connecting the query origin
   * to the initial boarding stop.
   */
  private createAccessEdge(edge: AccessEdge): string[] {
    const fromNodeId = this.stationNodeId(edge.from);
    const toNodeId = this.stationNodeId(edge.to);
    const color = DOT_CONFIG.colors.defaultRound;
    const ovalId = this.accessEdgeNodeId(edge.from, edge.to);
    const label = `Walk\\n${durationToString(edge.duration)}`;

    return [
      `  "${ovalId}" [label="${label}" shape=oval style="dashed,filled" fillcolor="white" color="${color}"];`,
      `  "${fromNodeId}" -> "${ovalId}" [color="${color}" style="dashed"];`,
      `  "${ovalId}" -> "${toNodeId}" [color="${color}" style="dashed"];`,
    ];
  }

  /**
   * Creates a transfer edge with transfer information oval in the middle.
   */
  private createTransferEdge(edge: TransferEdge, round: number): string[] {
    const fromNodeId = this.stationNodeId(edge.from);
    const toNodeId = this.stationNodeId(edge.to);
    const roundColor = this.getRoundColor(round);
    const transferOvalId = this.transferEdgeNodeId(edge.from, edge.to, round);

    const transferTime =
      edge.minTransferTime !== undefined
        ? durationToString(edge.minTransferTime)
        : 'N/A';
    const escapedTransferTime = this.escapeDotString(transferTime);
    const ovalLabel = `Transfer\\n${escapedTransferTime}`;

    return [
      `  "${transferOvalId}" [label="${ovalLabel}" shape=oval style="dashed,filled" fillcolor="white" color="${roundColor}"];`,
      `  "${fromNodeId}" -> "${transferOvalId}" [color="${roundColor}" style="dashed"];`,
      `  "${transferOvalId}" -> "${toNodeId}" [color="${roundColor}" style="dashed"];`,
    ];
  }

  /**
   * Creates a continuation edge to visually link trip continuations.
   */
  private createContinuationEdge(
    fromEdge: VehicleEdge,
    toEdge: VehicleEdge,
    round: number,
  ): string[] {
    const fromStopId = this.getVehicleEdgeToStopId(fromEdge);
    const toStopId = this.getVehicleEdgeFromStopId(toEdge);
    if (!fromStopId || !toStopId) {
      return [];
    }

    const fromStationId = this.stationNodeId(fromStopId);
    const toStationId = this.stationNodeId(toStopId);
    const roundColor = this.getRoundColor(round);
    const continuationOvalId = this.continuationNodeId(
      fromStopId,
      toStopId,
      round,
    );

    const fromRoute = this.result.timetable.getRoute(fromEdge.routeId);
    const toRoute = this.result.timetable.getRoute(toEdge.routeId);

    const fromServiceRouteInfo = fromRoute
      ? this.result.timetable.getServiceRouteInfo(fromRoute)
      : null;
    const toServiceRouteInfo = toRoute
      ? this.result.timetable.getServiceRouteInfo(toRoute)
      : null;

    const fromRouteName =
      fromServiceRouteInfo?.name ?? `Route ${String(fromEdge.routeId)}`;
    const toRouteName =
      toServiceRouteInfo?.name ?? `Route ${String(toEdge.routeId)}`;

    const fromRouteType = fromServiceRouteInfo
      ? routeTypeToString(fromServiceRouteInfo.type)
      : 'UNKNOWN';
    const toRouteType = toServiceRouteInfo
      ? routeTypeToString(toServiceRouteInfo.type)
      : 'UNKNOWN';

    const fromArrivalTime = timeToString(fromEdge.arrival);
    const toDepartureTime = toRoute
      ? timeToString(toRoute.departureFrom(toEdge.stopIndex, toEdge.tripIndex))
      : 'N/A';

    const escapedFromRouteName = this.escapeDotString(fromRouteName);
    const escapedToRouteName = this.escapeDotString(toRouteName);
    const escapedFromRouteType = this.escapeDotString(fromRouteType);
    const escapedToRouteType = this.escapeDotString(toRouteType);

    const fromRouteInfo = `${fromEdge.routeId}:${fromEdge.tripIndex}`;
    const toRouteInfo = `${toEdge.routeId}:${toEdge.tripIndex}`;

    const ovalLabel = `${escapedFromRouteType} ${escapedFromRouteName} (${fromRouteInfo}) ${fromArrivalTime}\\n↓\\n${escapedToRouteType} ${escapedToRouteName} (${toRouteInfo}) ${toDepartureTime}`;

    const { continuationFill } = DOT_CONFIG.colors;
    const { continuation: penWidth, continuationEdge: edgePenWidth } =
      DOT_CONFIG.penWidth;

    return [
      `  "${continuationOvalId}" [label="${ovalLabel}" shape=oval style="filled,bold" fillcolor="${continuationFill}" color="${roundColor}" penwidth="${penWidth}"];`,
      `  "${fromStationId}" -> "${continuationOvalId}" [color="${roundColor}" style="bold" penwidth="${edgePenWidth}"];`,
      `  "${continuationOvalId}" -> "${toStationId}" [color="${roundColor}" style="bold" penwidth="${edgePenWidth}"];`,
    ];
  }

  /**
   * Collects all stations that appear in the routing graph.
   */
  private collectStations(): Set<StopId> {
    const stations = new Set<StopId>();
    const graph = this.result.routingState.graph;

    for (const roundEdges of graph) {
      for (let stopId = 0; stopId < roundEdges.length; stopId++) {
        const edge = roundEdges[stopId];
        if (edge === undefined) continue;
        stations.add(stopId);
        if (isVehicleEdge(edge)) {
          const fromStopId = this.getVehicleEdgeFromStopId(edge);
          const toStopId = this.getVehicleEdgeToStopId(edge);
          if (fromStopId) stations.add(fromStopId);
          if (toStopId) stations.add(toStopId);
        } else if (isAccessEdge(edge)) {
          // Ensure the query origin (edge.from) is always collected even when
          // its own OriginNode hasn't been processed yet in this iteration.
          stations.add(edge.from);
          stations.add(edge.to);
        }
      }
    }

    return stations;
  }

  /**
   * Collects all continuation edges from a vehicle edge chain.
   */
  private collectContinuationChain(edge: VehicleEdge, round: number): string[] {
    const continuationEdges: string[] = [];
    let currentEdge = edge;
    let previousEdge = edge.continuationOf;

    while (previousEdge) {
      const edgeParts = this.createContinuationEdge(
        previousEdge,
        currentEdge,
        round,
      );
      continuationEdges.push(...edgeParts);

      currentEdge = previousEdge;
      previousEdge = previousEdge.continuationOf;
    }

    return continuationEdges;
  }

  /**
   * Collects all edges for the routing graph.
   */
  private collectEdges(): string[] {
    const edges: string[] = [];
    const continuationEdges: string[] = [];
    const graph = this.result.routingState.graph;

    for (let round = 0; round < graph.length; round++) {
      const roundEdges = graph[round];
      if (!roundEdges) continue;

      for (let stopId = 0; stopId < roundEdges.length; stopId++) {
        const edge = roundEdges[stopId];
        if (edge === undefined) continue;

        if (round === 0) {
          // Round 0 holds OriginNodes (no edge to draw) and AccessEdges
          // (walking legs from the query origin to the first boarding stop).
          if (isAccessEdge(edge)) {
            edges.push(...this.createAccessEdge(edge));
          }
          continue;
        }

        if (isVehicleEdge(edge)) {
          edges.push(...this.createVehicleEdge(edge, round));

          if (edge.continuationOf) {
            continuationEdges.push(
              ...this.collectContinuationChain(edge, round),
            );
          }
        } else if (isTransferEdge(edge)) {
          edges.push(...this.createTransferEdge(edge, round));
        }
      }
    }

    return [...edges, ...continuationEdges];
  }

  /**
   * Plots the routing graph as a DOT graph for visualization.
   *
   * @returns A string containing the DOT graph representation.
   */
  plotDotGraph(): string {
    const stations = this.collectStations();
    const edges = this.collectEdges();

    const builder = new DotBuilder();
    builder.addHeader();
    builder.addComment('Stations');

    for (const stopId of stations) {
      const stationNode = this.createStationNode(stopId);
      if (stationNode) {
        builder.addRaw([stationNode]);
      }
    }

    builder.addComment('Edges');
    builder.addRaw(edges);

    return builder.build();
  }
}