package main

import (
	"errors"
	"net/url"
)

type u struct{}

func (u) Execute(args []string, ins []<-chan Datum, out chan Datum) error {
	defer func() {
		out <- Datum{End: true}
		close(out)
	}()
	if len(args) != 1 && args[0] != "param" {
		return errors.New("usage: " + args[0])
	}
	for _, d := Select(ins); d != nil; _, d = Select(ins) {
		if d.End {
			continue
		}
		if d.Text == nil {
			return errors.New("type error: expected text, got html")
		}
		if args[0] == "urlescape" {
			ret := url.PathEscape(*d.Text)
			out <- Datum{Text: &ret}
			continue
		}
		if args[0] == "urlunescape" {
			ret, err := url.PathUnescape(*d.Text)
			if err != nil {
				return err
			}
			out <- Datum{Text: &ret}
			continue
		}
		p, err := url.Parse(*d.Text)
		if err != nil {
			return err
		}
		var ret string
		switch args[0] {
		case "scheme":
			ret = p.Scheme
		case "opaque":
			ret = p.Opaque
		case "host":
			ret = p.Host
		case "path":
			ret = p.Path
		case "param":
			if len(args) != 1 {
				vs := p.Query()
				for _, arg := range args[1:] {
					if v := vs.Get(arg); v != "" {
						out <- Datum{Text: &v}
					}
				}
				continue
			}
			ret = p.RawQuery
		case "fragment":
			ret = p.Fragment
		}
		out <- Datum{Text: &ret}
	}
	return nil
}

func init() {
	Filters["scheme"] = u{}
	Filters["opaque"] = u{}
	Filters["host"] = u{}
	Filters["path"] = u{}
	Filters["param"] = u{}
	Filters["fragment"] = u{}
	Filters["urlescape"] = u{}
	Filters["urlunescape"] = u{}
}