mirror of
https://github.com/OpenSquawk/OpenSquawk
synced 2026-08-02 23:18:40 +08:00
a9f6e6df42
genSquawk() drew a decimal number in 1000-8999, so clearances could contain the digits 8 or 9 — codes no transponder can dial. Replace it with a shared generateSquawk() that draws four octal digits and re-rolls the reserved codes (7500/7600/7700, 7000, 2000, 1200, 0000). shared/learn/scenario.ts had its own octal generator that could still draw an emergency code; it now uses the same helper. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
40 lines
1.5 KiB
TypeScript
40 lines
1.5 KiB
TypeScript
/**
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* Transponder (SSR) code generation.
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*
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* A squawk is an *octal* four-digit code — every digit is 0–7, because each
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* digit is encoded in three pulse positions. A code containing 8 or 9 cannot be
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* dialled into a real transponder, so it must never reach a clearance.
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*/
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/**
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* Codes ATC will not assign as a discrete code.
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*
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* 7500/7600/7700 are the ICAO emergency codes (unlawful interference, radio
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* failure, general emergency); 7000 is the European VFR conspicuity code and
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* 1200 its US equivalent; 2000 is the code for entering from a non-SSR area;
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* 0000 is a non-code used to indicate a transponder fault.
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*/
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export const RESERVED_SQUAWKS = new Set([
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'7500', '7600', '7700', '7000', '2000', '1200', '0000',
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])
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/** True when `code` is a well-formed, assignable discrete squawk. */
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export function isValidSquawk(code: string): boolean {
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if (!/^[0-7]{4}$/.test(code)) return false
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return !RESERVED_SQUAWKS.has(code)
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}
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/** A random assignable discrete squawk: four octal digits, no reserved code. */
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export function generateSquawk(): string {
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// The reserved set is tiny next to the 4096-code space, so re-rolling
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// terminates immediately in practice; the bound just makes that guaranteed.
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for (let attempt = 0; attempt < 20; attempt++) {
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let code = ''
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for (let digit = 0; digit < 4; digit++) {
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code += String(Math.floor(Math.random() * 8))
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}
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if (isValidSquawk(code)) return code
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}
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return '1000'
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}
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