105 lines
3.5 KiB
JavaScript
105 lines
3.5 KiB
JavaScript
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'use strict'
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const { format, safe, safenot } = require('./safe-format')
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const { jaystring } = require('./javascript')
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/*
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* Construct a function from lines/blocks/if conditions.
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*
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* Returns a Function instance (makeFunction) or code in text format (makeModule).
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*/
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const INDENT_START = /[{[]/
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const INDENT_END = /[}\]]/
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module.exports = () => {
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const lines = []
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let indent = 0
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const pushLine = (line) => {
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if (INDENT_END.test(line.trim()[0])) indent--
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lines.push({ indent, code: line })
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if (INDENT_START.test(line[line.length - 1])) indent++
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}
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const build = () => {
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if (indent !== 0) throw new Error('Unexpected indent at build()')
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const joined = lines.map((line) => format('%w%s', line.indent * 2, line.code)).join('\n')
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return /^[a-z][a-z0-9]*$/i.test(joined) ? `return ${joined}` : `return (${joined})`
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}
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const processScope = (scope) => {
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const entries = Object.entries(scope)
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for (const [key, value] of entries) {
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if (!/^[a-z][a-z0-9]*$/i.test(key)) throw new Error('Unexpected scope key!')
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if (!(typeof value === 'function' || value instanceof RegExp))
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throw new Error('Unexpected scope value!')
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}
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return entries
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}
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return {
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optimizedOut: false, // some branch of code has been optimized out
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size: () => lines.length,
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write(fmt, ...args) {
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if (typeof fmt !== 'string') throw new Error('Format must be a string!')
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if (fmt.includes('\n')) throw new Error('Only single lines are supported')
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pushLine(format(fmt, ...args))
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return true // code was written
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},
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block(prefix, writeBody, noInline = false) {
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const oldIndent = indent
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this.write('%s {', prefix)
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const length = lines.length
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writeBody()
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if (length === lines.length) {
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// no lines inside block, unwind the block
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lines.pop()
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indent = oldIndent
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return false // nothing written
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} else if (length === lines.length - 1 && !noInline) {
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// a single line has been written, inline it if opt-in allows
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const { code } = lines[lines.length - 1]
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// check below is just for generating more readable code, it's safe to inline all !noInline
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if (!/^(if|for) /.test(code)) {
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lines.length -= 2
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indent = oldIndent
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return this.write('%s %s', prefix, code)
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}
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}
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return this.write('}')
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},
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if(condition, writeBody, writeElse) {
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if (`${condition}` === 'false') {
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if (writeElse) writeElse()
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if (writeBody) this.optimizedOut = true
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} else if (`${condition}` === 'true') {
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if (writeBody) writeBody()
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if (writeElse) this.optimizedOut = true
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} else if (writeBody && this.block(format('if (%s)', condition), writeBody, !!writeElse)) {
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if (writeElse) this.block(format('else'), writeElse) // !!writeElse above ensures {} wrapping before `else`
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} else if (writeElse) {
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this.if(safenot(condition), writeElse)
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}
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},
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makeModule(scope = {}) {
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const scopeDefs = processScope(scope).map(
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([key, val]) => `const ${safe(key)} = ${jaystring(val)};`
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)
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return `(function() {\n'use strict'\n${scopeDefs.join('\n')}\n${build()}})()`
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},
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makeFunction(scope = {}) {
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const scopeEntries = processScope(scope)
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const keys = scopeEntries.map((entry) => entry[0])
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const vals = scopeEntries.map((entry) => entry[1])
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// eslint-disable-next-line no-new-func
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return Function(...keys, `'use strict'\n${build()}`)(...vals)
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},
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}
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}
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