import { SWEEP_CONTENDED, sweepHeld, swept } from "../strings/sweep.strings.ts";
import { appendFileSync, existsSync, readFileSync, writeFileSync } from "node:fs";

import { itemSpans, seenItems, spanText, withoutSpans } from "../resolvers/sweep.resolver.ts";
import { resolve } from "node:path";
import { wasDelivered } from "../registries/snapshot.registry.ts";

const HEADING = "\n## board sweep: items every addressee has written past\n\n";

export interface SweepOutcome {
    readonly swept: readonly string[];
    readonly message: string;
}

export const runSweep = function runSweep(repoRoot: string, absolute: string, archive: string): SweepOutcome {
    if (!existsSync(absolute)) {
        return { message: "", swept: [] };
    }

    const before = readFileSync(absolute, "utf8");

    const written = seenItems(itemSpans(before));
    if (written.length === 0) {
        return { message: "", swept: [] };
    }

    const held: string[] = [];
    const seen: typeof written = [];

    for (const span of written) {
        const unread = span.to.filter((reader) => !wasDelivered(repoRoot, reader, span.key));
        if (unread.length === 0) {
            seen.push(span);
            continue;
        }
        held.push(`${span.key} → ${unread.join(", ")}`);
    }

    const holdNote = held.length === 0 ? "" : sweepHeld(held);

    if (seen.length === 0) {
        return { message: holdNote, swept: [] };
    }

    const entries = seen.map(
        (span) =>
            `\n### ${span.key} — to ${span.to.join(", ")} · every addressee was handed this item in a delivered read\n\n${spanText(before, span)}\n`,
    );

    const witness = readFileSync(absolute, "utf8");
    if (witness !== before) {
        return { message: SWEEP_CONTENDED, swept: [] };
    }

    const target = resolve(repoRoot, archive);
    appendFileSync(target, existsSync(target) ? entries.join("") : `${HEADING}${entries.join("")}`, "utf8");

    writeFileSync(absolute, withoutSpans(before, seen), "utf8");

    const keys = seen.map((span) => span.key);

    return { message: `${holdNote}${swept(keys)}`, swept: keys };
};