import type { RPGCondition, RPGVariables } from "./types";

type ConditionOperator = '==' | '!=' | '>' | '<' | '>=' | '<=' | 'null' | '~null';
type ConditionValue = string | number | boolean | null;

export interface ParsedCondition {
    variable: string;
    negate: boolean;
    operator?: ConditionOperator;
    value?: ConditionValue;
}

export function parseCondition(s: RPGCondition): ParsedCondition {
    // ~variable — falsy check, nothing else allowed
    if (s.startsWith('~') && !s.includes(' '))
        return { variable: s.slice(1), negate: true };

    const spaceIdx = s.indexOf(' ');
    if (spaceIdx === -1)
        return { variable: s, negate: false };

    const variable = s.slice(0, spaceIdx);
    const rest = s.slice(spaceIdx + 1).trim();

    if (rest === 'null') return { variable, negate: false, operator: 'null' };
    if (rest === '~null') return { variable, negate: false, operator: '~null' };

    const opMatch = rest.match(/^(==|!=|>=|<=|>|<)\s*(.+)$/);
    if (!opMatch) throw new Error(`Invalid condition: "${s}"`);

    const [, operator, rawValue] = opMatch;
    let value: ConditionValue;
    if (rawValue === 'null') value = null;
    else if (rawValue === 'true') value = true;
    else if (rawValue === 'false') value = false;
    else if (!isNaN(Number(rawValue))) value = Number(rawValue);
    else value = rawValue.replace(/^['"]|['"]$/g, '');

    return { variable, negate: false, operator: operator as ConditionOperator, value };
}

export function evaluateCondition({ variable, negate, operator, value }: ParsedCondition, variables: RPGVariables): boolean {
    const val = variables[variable];

    if (operator === 'null') return val == null;
    if (operator === '~null') return val != null;

    if (operator === undefined)
        return negate ? !Boolean(val) : Boolean(val);

    if (operator === '==') return val === value;
    if (operator === '!=') return val !== value;

    if (typeof val !== 'number' || typeof value !== 'number') return false;
    if (operator === '<') return val < value;
    if (operator === '>') return val > value;
    if (operator === '<=') return val <= value;
    if (operator === '>=') return val >= value;

    return false;
}

export function evaluateConditions(conditions: RPGCondition[], variables: RPGVariables): boolean {
    return conditions.every(c => evaluateCondition(parseCondition(c), variables));
}