// Copyright 2013 Julien Schmidt. All rights reserved.
// Based on the path package, Copyright 2009 The Go Authors.
// Use of this source code is governed by a BSD-style license that can be found
// at https://github.com/julienschmidt/httprouter/blob/master/LICENSE

package gin

import (
	"runtime"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
)

type cleanPathTest struct {
	path, result string
}

var cleanTests = []cleanPathTest{
	// Already clean
	{"/", "/"},
	{"/abc", "/abc"},
	{"/a/b/c", "/a/b/c"},
	{"/abc/", "/abc/"},
	{"/a/b/c/", "/a/b/c/"},

	// missing root
	{"", "/"},
	{"a", "/a"},
	{"a/", "/a/"},
	{"abc", "/abc"},
	{"abc/def", "/abc/def"},
	{"a/b/c", "/a/b/c"},

	// Remove doubled slash
	{"//", "/"},
	{"/abc//", "/abc/"},
	{"/abc/def//", "/abc/def/"},
	{"/a/b/c//", "/a/b/c/"},
	{"/abc//def//ghi", "/abc/def/ghi"},
	{"//abc", "/abc"},
	{"///abc", "/abc"},
	{"//abc//", "/abc/"},

	// Remove . elements
	{".", "/"},
	{"./", "/"},
	{"/abc/./def", "/abc/def"},
	{"/./abc/def", "/abc/def"},
	{"/abc/.", "/abc/"},

	// Remove .. elements
	{"..", "/"},
	{"../", "/"},
	{"../../", "/"},
	{"../..", "/"},
	{"../../abc", "/abc"},
	{"/abc/def/ghi/../jkl", "/abc/def/jkl"},
	{"/abc/def/../ghi/../jkl", "/abc/jkl"},
	{"/abc/def/..", "/abc"},
	{"/abc/def/../..", "/"},
	{"/abc/def/../../..", "/"},
	{"/abc/def/../../..", "/"},
	{"/abc/def/../../../ghi/jkl/../../../mno", "/mno"},

	// Combinations
	{"abc/./../def", "/def"},
	{"abc//./../def", "/def"},
	{"abc/../../././../def", "/def"},
}

func TestPathClean(t *testing.T) {
	for _, test := range cleanTests {
		assert.Equal(t, test.result, cleanPath(test.path))
		assert.Equal(t, test.result, cleanPath(test.result))
	}
}

func TestPathCleanMallocs(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping malloc count in short mode")
	}

	if runtime.GOMAXPROCS(0) > 1 {
		t.Skip("skipping malloc count; GOMAXPROCS>1")
	}

	for _, test := range cleanTests {
		allocs := testing.AllocsPerRun(100, func() { cleanPath(test.result) })
		assert.InDelta(t, 0, allocs, 0.01)
	}
}

func BenchmarkPathClean(b *testing.B) {
	b.ReportAllocs()

	for b.Loop() {
		for _, test := range cleanTests {
			cleanPath(test.path)
		}
	}
}

func genLongPaths() (testPaths []cleanPathTest) {
	for i := 1; i <= 1234; i++ {
		ss := strings.Repeat("a", i)

		correctPath := "/" + ss
		testPaths = append(testPaths, cleanPathTest{
			path:   correctPath,
			result: correctPath,
		}, cleanPathTest{
			path:   ss,
			result: correctPath,
		}, cleanPathTest{
			path:   "//" + ss,
			result: correctPath,
		}, cleanPathTest{
			path:   "/" + ss + "/b/..",
			result: correctPath,
		})
	}
	return
}

func TestPathCleanLong(t *testing.T) {
	cleanTests := genLongPaths()

	for _, test := range cleanTests {
		assert.Equal(t, test.result, cleanPath(test.path))
		assert.Equal(t, test.result, cleanPath(test.result))
	}
}

func BenchmarkPathCleanLong(b *testing.B) {
	cleanTests := genLongPaths()

	b.ReportAllocs()

	for b.Loop() {
		for _, test := range cleanTests {
			cleanPath(test.path)
		}
	}
}

func cleanPathOld(p string) string {
	const stackBufSize = 128
	// Turn empty string into "/"
	if p == "" {
		return "/"
	}

	// Reasonably sized buffer on stack to avoid allocations in the common case.
	// If a larger buffer is required, it gets allocated dynamically.
	buf := make([]byte, 0, stackBufSize)

	n := len(p)

	// Invariants:
	//      reading from path; r is index of next byte to process.
	//      writing to buf; w is index of next byte to write.

	// path must start with '/'
	r := 1
	w := 1

	if p[0] != '/' {
		r = 0

		if n+1 > stackBufSize {
			buf = make([]byte, n+1)
		} else {
			buf = buf[:n+1]
		}
		buf[0] = '/'
	}

	trailing := n > 1 && p[n-1] == '/'

	// A bit more clunky without a 'lazybuf' like the path package, but the loop
	// gets completely inlined (bufApp calls).
	// loop has no expensive function calls (except 1x make)		// So in contrast to the path package this loop has no expensive function
	// calls (except make, if needed).

	for r < n {
		switch {
		case p[r] == '/':
			// empty path element, trailing slash is added after the end
			r++

		case p[r] == '.' && r+1 == n:
			trailing = true
			r++

		case p[r] == '.' && p[r+1] == '/':
			// . element
			r += 2

		case p[r] == '.' && p[r+1] == '.' && (r+2 == n || p[r+2] == '/'):
			// .. element: remove to last /
			r += 3

			if w > 1 {
				// can backtrack
				w--

				if len(buf) == 0 {
					for w > 1 && p[w] != '/' {
						w--
					}
				} else {
					for w > 1 && buf[w] != '/' {
						w--
					}
				}
			}

		default:
			// Real path element.
			// Add slash if needed
			if w > 1 {
				bufApp(&buf, p, w, '/')
				w++
			}

			// Copy element
			for r < n && p[r] != '/' {
				bufApp(&buf, p, w, p[r])
				w++
				r++
			}
		}
	}

	// Re-append trailing slash
	if trailing && w > 1 {
		bufApp(&buf, p, w, '/')
		w++
	}

	// If the original string was not modified (or only shortened at the end),
	// return the respective substring of the original string.
	// Otherwise return a new string from the buffer.
	if len(buf) == 0 {
		return p[:w]
	}
	return string(buf[:w])
}

func BenchmarkPathCleanOld(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		for _, test := range cleanTests {
			cleanPathOld(test.path)
		}
	}
}