/*
 *     Copyright 2020 The Dragonfly Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package source

import "net/textproto"

const (
	LastModified    = "X-Dragonfly-Last-Modified"
	IfModifiedSince = "X-Dragonfly-If-Modified-Since"
	ETag            = "X-Dragonfly-ETag"
	IfNoneMatch     = "X-Dragonfly-If-None-Match"
	Range           = "X-Dragonfly-Range" // startIndex-endIndex
)

const LastModifiedLayout = "Mon, 02 Jan 2006 15:04:05 GMT"

type ExpireInfo struct {
	LastModified string // Mon, 02 Jan 2006 15:04:05 GMT
	ETag         string
}

// A Header represents the key-value pairs in a Dragonfly source header.
//
// The keys should be in canonical form, as returned by
// CanonicalHeaderKey.
type Header map[string][]string

// Add adds the key, value pair to the header.
// It appends to any existing values associated with key.
// The key is case insensitive; it is canonicalized by
// CanonicalHeaderKey.
func (h Header) Add(key, value string) {
	textproto.MIMEHeader(h).Add(key, value)
}

// Set sets the header entries associated with key to the
// single element value. It replaces any existing values
// associated with key. The key is case insensitive; it is
// canonicalized by textproto.CanonicalMIMEHeaderKey.
// To use non-canonical keys, assign to the map directly.
func (h Header) Set(key, value string) {
	textproto.MIMEHeader(h).Set(key, value)
}

// Get gets the first value associated with the given key. If
// there are no values associated with the key, Get returns "".
// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
// used to canonicalize the provided key. To use non-canonical keys,
// access the map directly.
func (h Header) Get(key string) string {
	return textproto.MIMEHeader(h).Get(key)
}

// Values returns all values associated with the given key.
// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
// used to canonicalize the provided key. To use non-canonical
// keys, access the map directly.
// The returned slice is not a copy.
func (h Header) Values(key string) []string {
	return textproto.MIMEHeader(h).Values(key)
}

// get is like Get, but key must already be in CanonicalHeaderKey form.
func (h Header) get(key string) string {
	if v := h[key]; len(v) > 0 {
		return v[0]
	}
	return ""
}

// has reports whether h has the provided key defined, even if it's
// set to 0-length slice.
func (h Header) has(key string) bool {
	_, ok := h[key]
	return ok
}

// Del deletes the values associated with key.
// The key is case insensitive; it is canonicalized by
// CanonicalHeaderKey.
func (h Header) Del(key string) {
	textproto.MIMEHeader(h).Del(key)
}

// Clone returns a copy of h or nil if h is nil.
func (h Header) Clone() Header {
	if h == nil {
		return nil
	}

	// Find total number of values.
	nv := 0
	for _, vv := range h {
		nv += len(vv)
	}
	sv := make([]string, nv) // shared backing array for headers' values
	h2 := make(Header, len(h))
	for k, vv := range h {
		n := copy(sv, vv)
		h2[k] = sv[:n:n]
		sv = sv[n:]
	}
	return h2
}

func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }