Bot: Aura67 - Defector

Avg score
8.568
Wins
1228
Losses
2386
Win rate
11.4%
Score history

Avg: 8.568
Recent battles

Source

export default function bot({ history }) {
    if (history.length === 0) return ["C", null];

    const opponent = history.map(round => round.opponent);
    const recentDefections = opponent.slice(-8).filter(move => move === "D").length;
    const totalDefections = opponent.filter(move => move === "D").length;

    let   coopAfterC =  0;
    let   defectAfterC = 0;
    let   coopAfterD =  0;
    let   defectAfterD = 0;

    //How the opponent hasresponded to our previous moves
    for (let i = 1; i < history.length; i++) {
        const ourPreviousMove = history[i - 1].you;
        const theirMove = history[i].opponent;

        if (ourPreviousMove === "C") {
            if (theirMove === "C") coopAfterC++;
            else defectAfterC++;
        } else {
            if (theirMove === "C") coopAfterD++;
            else defectAfterD++;
        }
    }

    const chanceCooperationAfterC =
        (coopAfterC + 1) / (coopAfterC + defectAfterC + 2);

    const chanceCooperationAfterD =
        (coopAfterD + 1) / (coopAfterD + defectAfterD + 2);

    const timesWeDefected = coopAfterC + defectAfterC;
    const defectionRate = totalDefections / history.length;
    const lastMove = opponent[opponent.length - 1];

    // Clearly hostile Opponent response on defending always
    if (
        recentDefections >= 5 ||
        (history.length >= 10 && defectionRate > 0.6)
    ) {
        return ["D", null];
    }

    // When opponent  is forgiving: takeing advantage of their cooperation
    if (
        timesWeDefected >= 3 &&
        chanceCooperationAfterD >= 0.8 &&
        chanceCooperationAfterC >= 0.7
    ) {
        return ["D", null];
    }

    // Retaliating one time against a defection
    if (lastMove === "D") {
        return ["D", null];
    }

    // Keeping beneficial cooperations alive
    return ["C", null];
}