// Copyright 2015 The LUCI 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 isolate

import (
	"log"
	"path"
	"runtime"
	"strings"

	"github.com/luci/luci-go/common/errors"
)

// TODO(tandrii): Remove this hacky stuff.
// hacky stuff for faster debugging.
func assertNoError(err error) {
	if err == nil {
		return
	}
	log.Panic(errors.RenderStack(errors.Annotate(err, "assertion failed").Err()))
}

func assert(condition bool, info ...interface{}) {
	if condition {
		return
	}
	if len(info) == 0 {
		log.Panic(errors.RenderStack(errors.New("assertion failed")))
	} else if format, ok := info[0].(string); ok {
		log.Panic(errors.RenderStack(errors.Reason("assertion failed: "+format, info[1:]...).Err()))
	}
}

// uniqueMergeSortedStrings merges two sorted sets of string (as slices) and removes duplicates.
func uniqueMergeSortedStrings(ls, rs []string) []string {
	varSet := make([]string, len(ls)+len(rs))
	for i := 0; ; i++ {
		if len(ls) == 0 {
			rs, ls = ls, rs
		}
		if len(rs) == 0 {
			i += copy(varSet[i:], ls)
			return varSet[:i]
		}
		assert(i < len(varSet))
		assert(len(rs) > 0 && len(ls) > 0)
		if ls[0] > rs[0] {
			ls, rs = rs, ls
		}
		if ls[0] < rs[0] {
			varSet[i] = ls[0]
			ls = ls[1:]
		} else {
			varSet[i] = ls[0]
			ls, rs = ls[1:], rs[1:]
		}
	}
}

// posixRel returns a relative path that is lexically equivalent to targpath when
// joined to basepath with an intervening separator.
//
// That is, Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
// On success, the returned path will always be relative to basepath,
// even if basepath and targpath share no elements.
// An error is returned if targpath can't be made relative to basepath or if
// knowing the current working directory would be necessary to compute it.
//
// Copy-pasted & slightly edited from Go's lib path/filepath/path.go .
//
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
func posixRel(basepath, targpath string) (string, error) {
	base := path.Clean(basepath)
	targ := path.Clean(targpath)
	if targ == base {
		return ".", nil
	}
	if base == "." {
		base = ""
	}
	if path.IsAbs(base) != path.IsAbs(targ) {
		return "", errors.New("Rel: can't make " + targ + " relative to " + base)
	}
	// Position base[b0:bi] and targ[t0:ti] at the first differing elements.
	bl := len(base)
	tl := len(targ)
	var b0, bi, t0, ti int
	for {
		for bi < bl && base[bi] != '/' {
			bi++
		}
		for ti < tl && targ[ti] != '/' {
			ti++
		}
		if targ[t0:ti] != base[b0:bi] {
			break
		}
		if bi < bl {
			bi++
		}
		if ti < tl {
			ti++
		}
		b0 = bi
		t0 = ti
	}
	if base[b0:bi] == ".." {
		return "", errors.New("Rel: can't make " + targ + " relative to " + base)
	}
	if b0 != bl {
		// Base elements left. Must go up before going down.
		seps := strings.Count(base[b0:bl], string('/'))
		size := 2 + seps*3
		if tl != t0 {
			size += 1 + tl - t0
		}
		buf := make([]byte, size)
		n := copy(buf, "..")
		for i := 0; i < seps; i++ {
			buf[n] = '/'
			copy(buf[n+1:], "..")
			n += 3
		}
		if t0 != tl {
			buf[n] = '/'
			copy(buf[n+1:], targ[t0:])
		}
		return string(buf), nil
	}
	return targ[t0:], nil
}

// IsWindows returns True when running on the best OS there is.
func IsWindows() bool {
	return runtime.GOOS == "windows"
}