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67 lines
2.2 KiB
67 lines
2.2 KiB
// Limited implementation of python % string operator, supports only %s and %r for now |
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// (other formats are not used here, but may appear in custom templates) |
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'use strict' |
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const { inspect } = require('util') |
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module.exports = function sub(pattern, ...values) { |
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let regex = /%(?:(%)|(-)?(\*)?(?:\((\w+)\))?([A-Za-z]))/g |
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let result = pattern.replace(regex, function (_, is_literal, is_left_align, is_padded, name, format) { |
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if (is_literal) return '%' |
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let padded_count = 0 |
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if (is_padded) { |
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if (values.length === 0) throw new TypeError('not enough arguments for format string') |
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padded_count = values.shift() |
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if (!Number.isInteger(padded_count)) throw new TypeError('* wants int') |
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} |
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let str |
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if (name !== undefined) { |
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let dict = values[0] |
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if (typeof dict !== 'object' || dict === null) throw new TypeError('format requires a mapping') |
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if (!(name in dict)) throw new TypeError(`no such key: '${name}'`) |
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str = dict[name] |
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} else { |
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if (values.length === 0) throw new TypeError('not enough arguments for format string') |
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str = values.shift() |
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} |
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switch (format) { |
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case 's': |
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str = String(str) |
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break |
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case 'r': |
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str = inspect(str) |
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break |
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case 'd': |
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case 'i': |
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if (typeof str !== 'number') { |
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throw new TypeError(`%${format} format: a number is required, not ${typeof str}`) |
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} |
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str = String(str.toFixed(0)) |
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break |
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default: |
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throw new TypeError(`unsupported format character '${format}'`) |
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} |
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if (padded_count > 0) { |
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return is_left_align ? str.padEnd(padded_count) : str.padStart(padded_count) |
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} else { |
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return str |
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} |
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}) |
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if (values.length) { |
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if (values.length === 1 && typeof values[0] === 'object' && values[0] !== null) { |
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// mapping |
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} else { |
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throw new TypeError('not all arguments converted during string formatting') |
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} |
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} |
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return result |
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}
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