function evaluateWhen(properties, condition) {
    if (!condition) return true;
    if (condition.OR) return condition.OR.some(sub => evaluateWhen(properties, sub));
    if (condition.AND) return condition.AND.every(sub => evaluateWhen(properties, sub));

    for (const [key, val] of Object.entries(condition)) {
        if (key === 'OR' || key === 'AND') continue;
        const prop = properties[key];
        if (typeof val === 'string' && val.includes('|')) {
            if (!val.split('|').includes(prop)) return false;
        } else if (prop !== val) {
            return false;
        }
    }
    return true;
}

export function resolveBlock(state, properties) {
    const parts = [];

    if (state.variants) {
        // Handle standard variants
        const propStr = Object.keys(properties).sort().map(k => `${k}=${properties[k]}`).join(',');
        let variantDef = state.variants[propStr] || state.variants[""] || state.variants["normal"];

        // --- NEW ERROR REPORTING ---
        if (!variantDef) {
            console.warn("Available states:", Object.keys(state.variants));
            throw new Error(
                `Failed to resolve block variant.\nRequested: "${propStr}"\nCheck the console for available states.`
            );
        }

        if (Array.isArray(variantDef)) variantDef = variantDef[0]; // Take first random model
        parts.push(variantDef);
    } else if (state.multipart) {
        // Handle multipart
        for (const part of state.multipart) {
            if (evaluateWhen(properties, part.when)) {
                let applyDef = part.apply;
                if (Array.isArray(applyDef)) applyDef = applyDef[0];
                parts.push(applyDef);
            }
        }

        if (parts.length === 0) {
            console.warn("Possibly malformed multipart block with no parts.")
        }
    }

    return parts;
}

export function getVariantHash(part) {
    // Uniquely identifies a baked geometry variant so we can pool instances
    return `${part.model}#y=${part.y || 0},x=${part.x || 0},uvlock=${!!part.uvlock}`;
}