const HEADING_LEAD = "### ";

const BACKTICK = "`";

const isLead = function isLead(candidate: string): boolean {
    if (candidate.length < 2) {
        return false;
    }
    if (!candidate.endsWith(":")) {
        return false;
    }

    for (const char of candidate.slice(0, -1)) {
        if (char < "A" || char > "Z") {
            return false;
        }
    }

    return true;
};

const CLASS_BOUND_MARKER = "presuppose a CLASS";

export const classBoundLeads = function classBoundLeads(accumulator: string): string[] {
    const out: string[] = [];

    for (const line of accumulator.split("\n")) {
        if (line.startsWith(HEADING_LEAD)) {
            break;
        }
        if (!line.includes(CLASS_BOUND_MARKER)) {
            continue;
        }

        let cursor = 0;
        while (cursor < line.length) {
            const open = line.indexOf(BACKTICK, cursor);
            if (open === -1) {
                break;
            }

            const close = line.indexOf(BACKTICK, open + 1);
            if (close === -1) {
                break;
            }

            const candidate = line.slice(open + 1, close).trim();
            if (isLead(candidate) && !out.includes(candidate)) {
                out.push(candidate);
            }
            cursor = close + 1;
        }
    }

    return out;
};

export const declaredLeads = function declaredLeads(accumulator: string): string[] {
    const out: string[] = [];

    for (const line of accumulator.split("\n")) {
        if (line.startsWith(HEADING_LEAD)) {
            break;
        }

        let cursor = 0;
        while (cursor < line.length) {
            const open = line.indexOf(BACKTICK, cursor);
            if (open === -1) {
                break;
            }

            const close = line.indexOf(BACKTICK, open + 1);
            if (close === -1) {
                break;
            }

            const candidate = line.slice(open + 1, close).trim();
            if (isLead(candidate) && !out.includes(candidate)) {
                out.push(candidate);
            }
            cursor = close + 1;
        }
    }

    return out;
};