53 lines
1.1 KiB
Go
53 lines
1.1 KiB
Go
package tree
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import (
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"fmt"
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)
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//Ctx represents the current context position, size, node, and the current filtered result
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type Ctx struct {
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NodeSet
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Pos int
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Size int
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}
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//Fn is a XPath function, written in Go
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type Fn func(c Ctx, args ...Result) (Result, error)
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//LastArgOpt sets whether the last argument in a function is optional, variadic, or neither
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type LastArgOpt int
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//LastArgOpt options
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const (
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None LastArgOpt = iota
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Optional
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Variadic
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)
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//Wrap interfaces XPath function calls with Go
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type Wrap struct {
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Fn Fn
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//NArgs represents the number of arguments to the XPath function. -1 represents a single optional argument
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NArgs int
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LastArgOpt LastArgOpt
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}
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//Call checks the arguments and calls Fn if they are valid
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func (w Wrap) Call(c Ctx, args ...Result) (Result, error) {
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switch w.LastArgOpt {
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case Optional:
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if len(args) == w.NArgs || len(args) == w.NArgs-1 {
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return w.Fn(c, args...)
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}
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case Variadic:
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if len(args) >= w.NArgs-1 {
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return w.Fn(c, args...)
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}
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default:
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if len(args) == w.NArgs {
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return w.Fn(c, args...)
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}
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}
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return nil, fmt.Errorf("Invalid number of arguments")
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}
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