import { HttpError } from '../../../services/HttpService';

//
// S4d Phase 2 slice 2 - why a send or a schedule was refused.
//
// THE SERVER'S MESSAGES ALREADY NAME THEIR REMEDY, so this module RELAYS them rather than
// carrying a second copy that drifts. What it adds is the two BEHAVIOURAL bits a message cannot
// express: may the client retry, and is the remedy "narrow the segment"?
//
// acknowledgedAudience.ts::AcknowledgedAudienceRefusal is the source of this vocabulary.
//

export type RefusalReason =
    | 'not-previewed' | 'preview-expired' | 'preview-incomplete' | 'preview-corrupt'
    | 'preview-truncated' | 'not-acknowledged' | 'audience-diverged'
    | 'unknown';

export interface CampaignRefusal {
    reason: RefusalReason;
    /** The server's own sentence. Never rewritten here. */
    message: string;
    /** The remedy is to make the segment smaller. Re-counting unchanged cannot help. */
    mustNarrow: boolean;
    /** Re-counting and trying again is a sensible next action. */
    retryable: boolean;
}

const KNOWN: Record<Exclude<RefusalReason, 'unknown'>, { mustNarrow: boolean; retryable: boolean }> = {
    'not-previewed':      { mustNarrow: false, retryable: true },
    'preview-expired':    { mustNarrow: false, retryable: true },
    'preview-incomplete': { mustNarrow: false, retryable: true },
    'preview-corrupt':    { mustNarrow: false, retryable: true },
    // NOT retryable. Re-running the identical segment truncates identically - a retry loop here
    // cannot terminate, which is why the server gives this its own reason instead of "expired".
    'preview-truncated':  { mustNarrow: true,  retryable: false },
    'not-acknowledged':   { mustNarrow: false, retryable: true },
    'audience-diverged':  { mustNarrow: false, retryable: true },
};

const GENERIC = 'We could not send this campaign. Please count the audience again and retry.';

const readBody = (error: unknown): { reason?: unknown; message?: unknown } => {
    if (!(error instanceof HttpError)) return {};
    const body = error.body;
    if (typeof body !== 'object' || body === null) return {};
    return body as { reason?: unknown; message?: unknown };
};

export function readRefusal(error: unknown): CampaignRefusal {
    const body = readBody(error);
    const serverMessage = typeof body.message === 'string' && body.message !== ''
        ? body.message
        : (error instanceof HttpError && error.message !== '' ? error.message : GENERIC);

    const rawReason = typeof body.reason === 'string' ? body.reason : '';
    if (rawReason !== '' && rawReason in KNOWN) {
        const reason = rawReason as Exclude<RefusalReason, 'unknown'>;
        return { reason, message: serverMessage, ...KNOWN[reason] };
    }

    // DEFAULT IS "we do not know why", never a guessed reason. Naming a cause we cannot establish
    // is what fixed on the unlock page and fixed on the receptionist search.
    return { reason: 'unknown', message: serverMessage, mustNarrow: false, retryable: true };
}