resolve.go

package iri

// Code in this file is derived from
// https://github.com/golang/go/blob/master/src/net/url/url.go

// License of original url.go code:
//
// Copyright (c) 2009 The Go Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

import "strings"

func resolveReference(base, ref IRI) IRI {
	result := ref
	if ref.hasScheme() {
		return result
	}
	result.Scheme = base.Scheme
	if ref.hasAuthority() {
		result.Path = resolvePath(ref.Path, "")
		return result
	}
	result.ForceAuthority = base.ForceAuthority
	result.Authority = base.Authority
	result.Path = resolvePath(base.Path, ref.Path)
	if ref.hasQuery() || (ref.Path != "") {
		return result
	}
	result.ForceQuery = base.ForceQuery
	result.Query = base.Query
	return result
}

// resolvePath applies special path segments from refs and applies
// them to base, per RFC 3986.
func resolvePath(base, ref string) string {
	var full string
	switch {
	case ref == "":
		full = base
	case ref[0] != '/':
		i := strings.LastIndex(base, "/")
		full = base[:i+1] + ref
	default:
		full = ref
	}
	if full == "" {
		return ""
	}

	var (
		last string
		elem string
		i    int
		dst  strings.Builder
	)
	first := true
	remaining := full
	for i >= 0 {
		i = strings.IndexByte(remaining, '/')
		if i < 0 {
			last, elem, remaining = remaining, remaining, ""
		} else {
			elem, remaining = remaining[:i], remaining[i+1:]
		}
		if elem == "." {
			first = false
			// drop
			continue
		}

		if elem == ".." {
			str := dst.String()
			index := strings.LastIndexByte(str, '/')

			dst.Reset()
			if index == -1 {
				first = true
			} else {
				dst.WriteString(str[:index])
			}
		} else {
			if !first {
				dst.WriteByte('/')
			}
			dst.WriteString(elem)
			first = false
		}
	}

	if last == "." || last == ".." {
		dst.WriteByte('/')
	}

	return "/" + strings.TrimPrefix(dst.String(), "/")
}