package url

import (
	"net/url"
	"sort"
	"strings"
)

// ParseQuery parses the URL-encoded query string and returns
// a map listing the values specified for each key.
// ParseQuery always returns a non-nil map containing all the
// valid query parameters found; err describes the first decoding error
// encountered, if any.
//
// Query is expected to be a list of key=value settings separated by
// ampersands or semicolons. A setting without an equals sign is
// interpreted as a key set to an empty value.
func ParseQuery(query string) (Values, error) {
	vs, err := url.ParseQuery(query)
	return Values(vs), err
}

// Values maps a string key to a list of values.
// It is typically used for query parameters and form values.
// Unlike in the http.Header map, the keys in a Values map
// are case-sensitive.
type Values map[string][]string

// Get gets the first value associated with the given key.
// If there are no values associated with the key, Get returns
// the empty string. To access multiple values, use the map
// directly.
func (v Values) Get(key string) string {
	if v == nil {
		return ""
	}
	vs := v[key]
	if len(vs) == 0 {
		return ""
	}
	return vs[0]
}

// Set sets the key to value. It replaces any existing
// values.
func (v Values) Set(key, value string) {
	v[key] = []string{value}
}

// Add adds the value to key. It appends to any existing
// values associated with key.
func (v Values) Add(key, value string) {
	v[key] = append(v[key], value)
}

// Del deletes the values associated with key.
func (v Values) Del(key string) {
	delete(v, key)
}

// Encode encodes the values into ``URL encoded'' form
// ("bar=baz&foo=quux") sorted by key.
func (v Values) Encode() string {
	if v == nil {
		return ""
	}
	var buf strings.Builder
	keys := make([]string, 0, len(v))
	for k := range v {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	for _, k := range keys {
		vs := v[k]
		keyEscaped := QueryEscape(k)
		for _, v := range vs {
			if buf.Len() > 0 {
				buf.WriteByte('&')
			}
			buf.WriteString(keyEscaped)
			buf.WriteByte('=')
			buf.WriteString(QueryEscape(v))
		}
	}
	return buf.String()
}
