bp-engine

Dota2 Captain's Mode Draft Engine - A TypeScript library for implementing the complete Ban/Pick flow.

Features

• Complete 24-step Captain's Mode draft sequence
• Decoupled first/second pick from Radiant/Dire teams
• TypeScript support with full type definitions
• Snapshot support for saving/resuming drafts
• Hero selection validation (prevent duplicates)

Installation

npm install bp-engine
# or
pnpm add bp-engine
# or
yarn add bp-engine

Usage

Basic Example

import { init, DRAFT_SEQUENCE } from 'bp-engine';

// Initialize a draft (Radiant as first pick)
const engine = init({
  isRadiantFirst: true,
});

// Start the draft
let turn = engine.start();
console.log(turn);
// { type: 'b', isRadiant: true, isEnd: false, stepIndex: 0, totalSteps: 24 }

// Process each turn
while (!turn.isEnd) {
  const heroId = await getUserSelection(turn); // Your UI logic
  turn = engine.select(heroId);
}

// Get final result
const result = engine.format();
// {
//   radiant: { bans: [...], picks: [...] },
//   dire: { bans: [...], picks: [...] },
//   currentStep: 24,
//   isComplete: true
// }

Team Configuration

The isRadiantFirst parameter determines which team goes first:

// Radiant goes first (先手方)
const engine = init({ isRadiantFirst: true });
// Step 0: Radiant bans
// Step 2: Dire bans

// Dire goes first (先手方)
const engine = init({ isRadiantFirst: false });
// Step 0: Dire bans
// Step 2: Radiant bans

Save/Resume Draft

// Save current state
const snapshot = engine.getSnapshot();
// Save to localStorage, database, etc.

// Resume later
const engine = init({
  isRadiantFirst: true,
  initialStates: snapshot,
});

Check Available Heroes

// Check if a hero can be selected
if (engine.canSelect(heroId)) {
  engine.select(heroId);
}

// Get all selected hero IDs
const selectedIds = engine.getSelectedHeroIds();

Draft Sequence

The default 24-step Captain's Mode sequence:

Round 1 BAN (7):
  First Pick:  2 bans
  Second Pick: 2 bans
  First Pick:  1 ban
  Second Pick: 2 bans

Round 1 PICK (6):
  First Pick:  1 pick
  Second Pick: 2 picks
  First Pick:  2 picks
  Second Pick: 1 pick

Round 2 BAN (4):
  Second Pick: 2 bans
  First Pick:  2 bans

Round 2 PICK (6):
  Second Pick: 2 picks
  First Pick:  1 pick
  Second Pick: 1 pick
  First Pick:  1 pick

Round 3 BAN (2):
  First Pick:  1 ban
  Second Pick: 1 ban

Final PICK (4):
  First Pick, Second Pick, First Pick, Second Pick

API Reference

init(config: BPEngineConfig): BPEngine

Factory function to create a new draft engine.

Config Options:

• isRadiantFirst (required): true if Radiant is first pick
• sequence (optional): Custom draft sequence (defaults to DRAFT_SEQUENCE)
• initialStates (optional): Snapshot to restore from

BPEngine Methods

| Method | Description | |--------|-------------| | start() | Start the draft, returns first TurnInfo | | select(heroId) | Select a hero for current turn, returns next TurnInfo | | undo() | Undo last selection | | getCurrentTurn() | Get current turn info without changing state | | canSelect(heroId) | Check if hero is available | | getSelectedHeroIds() | Get array of selected hero IDs | | getSnapshot() | Get current state array for saving | | format() | Get structured DraftState output |

Types

interface TurnInfo {
  type: 'b' | 'p';      // Current action (ban or pick)
  isRadiant: boolean;   // Is it Radiant's turn?
  isEnd: boolean;       // Draft complete?
  stepIndex: number;    // Current step (0-24)
  totalSteps: number;   // Always 24
}

interface DraftState {
  radiant: {
    bans: (number | null)[];   // 7 slots
    picks: (number | null)[];  // 5 slots
  };
  dire: {
    bans: (number | null)[];
    picks: (number | null)[];
  };
  currentStep: number;
  isComplete: boolean;
}

License

MIT