mirror of https://github.com/garrytan/gstack.git
35 lines
1.8 KiB
TypeScript
35 lines
1.8 KiB
TypeScript
// Lone Unicode surrogate sanitization.
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//
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// Lone surrogates (\uD800-\uDFFF without a matching pair) are valid UTF-16
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// but invalid UTF-8, so JSON.stringify produces output the Claude API rejects
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// with HTTP 400 "no low surrogate in string". Page captures from real-world
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// HTML hit this when content contains broken emoji bytes or mid-emoji splits.
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//
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// Two sanitizers are needed because both forms appear in browse responses:
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// - Raw UTF-16 surrogates in text/plain bodies (pre-stringify state).
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// - JSON \uXXXX escape sequences after JSON.stringify already ran.
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// Both replace lone surrogates with U+FFFD (replacement character).
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const LONE_SURROGATE_HIGH = /[\uD800-\uDBFF](?![\uDC00-\uDFFF])/g;
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const LONE_SURROGATE_LOW = /(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/g;
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export function stripLoneSurrogates(s: string): string {
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return s.replace(LONE_SURROGATE_HIGH, '<27>').replace(LONE_SURROGATE_LOW, '<27>');
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}
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// Matches \uD8XX-\uDFXX escape text where the pair is not completed by an
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// adjacent \uDC00-\uDFFF (high) or preceded by \uD800-\uDBFF (low).
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const LONE_SURROGATE_HIGH_ESCAPE = /\\u[Dd][89ABab][0-9A-Fa-f]{2}(?!\\u[Dd][C-Fc-f][0-9A-Fa-f]{2})/g;
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const LONE_SURROGATE_LOW_ESCAPE = /(?<!\\u[Dd][89ABab][0-9A-Fa-f]{2})\\u[Dd][C-Fc-f][0-9A-Fa-f]{2}/g;
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export function stripLoneSurrogateEscapes(s: string): string {
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return s.replace(LONE_SURROGATE_HIGH_ESCAPE, '\\uFFFD').replace(LONE_SURROGATE_LOW_ESCAPE, '\\uFFFD');
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}
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// Pick the right sanitizer based on whether the body has already been JSON-stringified.
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// For application/json bodies, run both passes: raw first (in case the JSON encoder
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// emitted surrogates as-is rather than escaping), then escape-text.
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export function sanitizeBody(body: string, isJson: boolean): string {
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return isJson ? stripLoneSurrogateEscapes(stripLoneSurrogates(body)) : stripLoneSurrogates(body);
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}
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