lemon
42 lines
1.7 KiB
TypeScript
42 lines
1.7 KiB
TypeScript
/**
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* Parse the amount from a BOLT11 invoice string.
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* Returns the amount in millisatoshis, or 0 if the invoice has no amount or cannot be parsed.
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*
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* BOLT11 encodes the amount in the human-readable part (HRP) of the bech32 string:
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* ln + <coin type> + [amount + multiplier]
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* The last `1` in the string separates the HRP from the data part.
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* The amount is optional — invoices with no amount (e.g. `lnbc1p...`) return 0.
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*/
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export function parseBolt11AmountMsats(bolt11: string | undefined): number {
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if (!bolt11) return 0;
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const lower = bolt11.toLowerCase();
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// Find the last '1' which separates HRP from data in bech32.
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const lastOne = lower.lastIndexOf('1');
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if (lastOne < 2) return 0;
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const hrp = lower.substring(0, lastOne);
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// HRP format: ln + coin type (bc/tb/bcrt/sb/ltc/tltc) + optional amount
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// Extract the amount+multiplier portion from the end of the HRP.
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const amountMatch = hrp.match(/(\d+)([munp]?)$/);
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if (!amountMatch) return 0; // No amount in HRP (zero-amount invoice)
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const value = parseInt(amountMatch[1], 10);
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if (isNaN(value) || value <= 0) return 0;
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// Convert to millisatoshis based on multiplier.
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// The numeric value represents BTC divided by the multiplier:
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// (none) = BTC, m = milli-BTC, u = micro-BTC, n = nano-BTC, p = pico-BTC
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// 1 BTC = 100_000_000_000 msats
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const multiplier = amountMatch[2];
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switch (multiplier) {
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case 'm': return value * 100_000_000; // milli-BTC: 1e8 msats
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case 'u': return value * 100_000; // micro-BTC: 1e5 msats
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case 'n': return value * 100; // nano-BTC: 1e2 msats
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case 'p': return value / 10; // pico-BTC: 0.1 msats
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default: return value * 100_000_000_000; // BTC: 1e11 msats
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}
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}
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