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fx/pkg/reducer/js.go

78 lines
1.2 KiB
Go

package reducer
import (
_ "embed"
"fmt"
"strings"
)
func js(args []string) string {
rs := "\n"
for i, a := range args {
rs += " try {"
switch {
case a == ".":
rs += `
x = function ()
{ return this }
.call(x)
`
case flatMapRegex.MatchString(a):
code := fold(strings.Split(a, "[]"))
rs += fmt.Sprintf(
`
x = (
%v
)(x)
`, code)
case strings.HasPrefix(a, ".["):
rs += fmt.Sprintf(
`
x = function ()
{ return this%v }
.call(x)
`, a[1:])
case strings.HasPrefix(a, "."):
rs += fmt.Sprintf(
`
x = function ()
{ return this%v }
.call(x)
`, a)
default:
rs += fmt.Sprintf(
`
let f = function ()
{ return %v }
.call(x)
x = typeof f === 'function' ? f(x) : f
`, a)
}
// Generate a beautiful error message.
rs += " } catch (e) {\n"
pre, post, pointer := trace(args, i)
rs += fmt.Sprintf(
" throw `\\n ${%q} ${%q} ${%q}\\n %v\\n\\n${e.stack || e}`\n",
pre, a, post, pointer,
)
rs += " }\n"
}
fn := `function reduce(input) {
let x = JSON.parse(input)
// Reducers %v
if (typeof x === 'undefined') {
return 'null'
} else {
return JSON.stringify(x)
}
}
`
return fmt.Sprintf(fn, rs)
}