52 lines
1.6 KiB
TypeScript
52 lines
1.6 KiB
TypeScript
/**
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* RFC 5322 §3.6.4 reply threading.
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*
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* Computes the In-Reply-To and References headers an outgoing reply must
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* carry so MUAs can stitch the conversation back together.
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*
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* In-Reply-To = parent.Message-ID
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* References = parent.References (if any) + parent.Message-ID
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*
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* Bare msg-ids only - angle brackets are stripped because JMAP RFC 8621
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* §4.1.2.3 stores Message-IDs without them.
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*/
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export interface ParentThreadingInfo {
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// JMAP RFC 8621 §4.1.2.3 specifies messageId as String[]|null, but the
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// codebase has historically typed it as string. Accept either shape.
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messageId?: string | string[];
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references?: string[];
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}
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export interface ReplyThreadingHeaders {
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inReplyTo: string[];
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references: string[];
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}
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export function stripMessageIdBrackets(id: string): string {
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return id.trim().replace(/^<+/, '').replace(/>+$/, '').trim();
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}
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export function computeReplyThreadingHeaders(
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parent: ParentThreadingInfo | undefined,
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): ReplyThreadingHeaders | null {
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const rawId = Array.isArray(parent?.messageId) ? parent.messageId[0] : parent?.messageId;
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const parentId = rawId ? stripMessageIdBrackets(rawId) : '';
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if (!parentId) return null;
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const ancestors = (parent?.references ?? [])
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.map(stripMessageIdBrackets)
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.filter(Boolean);
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// De-dupe while preserving order; the parent's id closes the chain.
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const seen = new Set<string>();
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const references: string[] = [];
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for (const id of [...ancestors, parentId]) {
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if (seen.has(id)) continue;
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seen.add(id);
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references.push(id);
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}
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return { inReplyTo: [parentId], references };
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}
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