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One of the proposals in #23328 This PR introduces a simple expression calculator (templates/eval/eval.go), it can do basic expression calculations. Many untested template helper functions like `Mul` `Add` can be replaced by this new approach. Then these `Add` / `Mul` / `percentage` / `Subtract` / `DiffStatsWidth` could all use this `Eval`. And it provides enhancements for Golang templates, and improves readability. Some examples: ---- * Before: `{{Add (Mul $glyph.Row 12) 12}}` * After: `{{Eval $glyph.Row "*" 12 "+" 12}}` ---- * Before: `{{if lt (Add $i 1) (len $.Topics)}}` * After: `{{if Eval $i "+" 1 "<" (len $.Topics)}}` ## FAQ ### Why not use an existing expression package? We need a highly customized expression engine: * do the calculation on the fly, without pre-compiling * deal with int/int64/float64 types, to make the result could be used in Golang template. * make the syntax could be used in the Golang template directly * do not introduce too much complex or strange syntax, we just need a simple calculator. * it needs to strictly follow Golang template's behavior, for example, Golang template treats all non-zero values as truth, but many 3rd packages don't do so. ### What's the benefit? * Developers don't need to add more `Add`/`Mul`/`Sub`-like functions, they were getting more and more. Now, only one `Eval` is enough for all cases. * The new code reads better than old `{{Add (Mul $glyph.Row 12) 12}}`, the old one isn't familiar to most procedural programming developers (eg, the Golang expression syntax). * The `Eval` is fully covered by tests, many old `Add`/`Mul`-like functions were never tested. ### The performance? It doesn't use `reflect`, it doesn't need to parse or compile when used in Golang template, the performance is as fast as native Go template. ### Is it too complex? Could it be unstable? The expression calculator program is a common homework for computer science students, and it's widely used as a teaching and practicing purpose for developers. The algorithm is pretty well-known. The behavior can be clearly defined, it is stable.
283 lines
6.2 KiB
Go
283 lines
6.2 KiB
Go
// Copyright 2017 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package util
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import (
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"bytes"
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"crypto/rand"
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"errors"
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"fmt"
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"math/big"
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"strconv"
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"strings"
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"golang.org/x/text/cases"
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"golang.org/x/text/language"
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)
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// OptionalBool a boolean that can be "null"
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type OptionalBool byte
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const (
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// OptionalBoolNone a "null" boolean value
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OptionalBoolNone OptionalBool = iota
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// OptionalBoolTrue a "true" boolean value
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OptionalBoolTrue
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// OptionalBoolFalse a "false" boolean value
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OptionalBoolFalse
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)
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// IsTrue return true if equal to OptionalBoolTrue
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func (o OptionalBool) IsTrue() bool {
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return o == OptionalBoolTrue
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}
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// IsFalse return true if equal to OptionalBoolFalse
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func (o OptionalBool) IsFalse() bool {
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return o == OptionalBoolFalse
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}
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// IsNone return true if equal to OptionalBoolNone
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func (o OptionalBool) IsNone() bool {
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return o == OptionalBoolNone
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}
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// OptionalBoolOf get the corresponding OptionalBool of a bool
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func OptionalBoolOf(b bool) OptionalBool {
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if b {
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return OptionalBoolTrue
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}
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return OptionalBoolFalse
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}
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// OptionalBoolParse get the corresponding OptionalBool of a string using strconv.ParseBool
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func OptionalBoolParse(s string) OptionalBool {
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b, e := strconv.ParseBool(s)
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if e != nil {
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return OptionalBoolNone
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}
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return OptionalBoolOf(b)
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}
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// Max max of two ints
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func Max(a, b int) int {
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if a < b {
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return b
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}
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return a
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}
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// Min min of two ints
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func Min(a, b int) int {
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if a > b {
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return b
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}
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return a
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}
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// IsEmptyString checks if the provided string is empty
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func IsEmptyString(s string) bool {
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return len(strings.TrimSpace(s)) == 0
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}
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// NormalizeEOL will convert Windows (CRLF) and Mac (CR) EOLs to UNIX (LF)
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func NormalizeEOL(input []byte) []byte {
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var right, left, pos int
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if right = bytes.IndexByte(input, '\r'); right == -1 {
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return input
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}
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length := len(input)
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tmp := make([]byte, length)
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// We know that left < length because otherwise right would be -1 from IndexByte.
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copy(tmp[pos:pos+right], input[left:left+right])
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pos += right
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tmp[pos] = '\n'
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left += right + 1
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pos++
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for left < length {
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if input[left] == '\n' {
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left++
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}
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right = bytes.IndexByte(input[left:], '\r')
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if right == -1 {
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copy(tmp[pos:], input[left:])
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pos += length - left
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break
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}
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copy(tmp[pos:pos+right], input[left:left+right])
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pos += right
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tmp[pos] = '\n'
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left += right + 1
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pos++
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}
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return tmp[:pos]
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}
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// MergeInto merges pairs of values into a "dict"
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func MergeInto(dict map[string]interface{}, values ...interface{}) (map[string]interface{}, error) {
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for i := 0; i < len(values); i++ {
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switch key := values[i].(type) {
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case string:
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i++
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if i == len(values) {
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return nil, errors.New("specify the key for non array values")
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}
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dict[key] = values[i]
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case map[string]interface{}:
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m := values[i].(map[string]interface{})
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for i, v := range m {
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dict[i] = v
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}
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default:
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return nil, errors.New("dict values must be maps")
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}
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}
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return dict, nil
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}
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// CryptoRandomInt returns a crypto random integer between 0 and limit, inclusive
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func CryptoRandomInt(limit int64) (int64, error) {
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rInt, err := rand.Int(rand.Reader, big.NewInt(limit))
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if err != nil {
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return 0, err
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}
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return rInt.Int64(), nil
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}
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const alphanumericalChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
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// CryptoRandomString generates a crypto random alphanumerical string, each byte is generated by [0,61] range
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func CryptoRandomString(length int64) (string, error) {
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buf := make([]byte, length)
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limit := int64(len(alphanumericalChars))
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for i := range buf {
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num, err := CryptoRandomInt(limit)
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if err != nil {
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return "", err
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}
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buf[i] = alphanumericalChars[num]
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}
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return string(buf), nil
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}
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// CryptoRandomBytes generates `length` crypto bytes
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// This differs from CryptoRandomString, as each byte in CryptoRandomString is generated by [0,61] range
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// This function generates totally random bytes, each byte is generated by [0,255] range
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func CryptoRandomBytes(length int64) ([]byte, error) {
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buf := make([]byte, length)
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_, err := rand.Read(buf)
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return buf, err
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}
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// ToUpperASCII returns s with all ASCII letters mapped to their upper case.
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func ToUpperASCII(s string) string {
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b := []byte(s)
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for i, c := range b {
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if 'a' <= c && c <= 'z' {
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b[i] -= 'a' - 'A'
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}
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}
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return string(b)
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}
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// ToTitleCase returns s with all english words capitalized
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func ToTitleCase(s string) string {
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// `cases.Title` is not thread-safe, do not use global shared variable for it
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return cases.Title(language.English).String(s)
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}
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// ToTitleCaseNoLower returns s with all english words capitalized without lower-casing
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func ToTitleCaseNoLower(s string) string {
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// `cases.Title` is not thread-safe, do not use global shared variable for it
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return cases.Title(language.English, cases.NoLower).String(s)
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}
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// ToInt64 transform a given int into int64.
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func ToInt64(number interface{}) (int64, error) {
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var value int64
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switch v := number.(type) {
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case int:
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value = int64(v)
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case int8:
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value = int64(v)
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case int16:
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value = int64(v)
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case int32:
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value = int64(v)
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case int64:
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value = v
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case uint:
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value = int64(v)
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case uint8:
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value = int64(v)
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case uint16:
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value = int64(v)
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case uint32:
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value = int64(v)
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case uint64:
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value = int64(v)
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case float32:
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value = int64(v)
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case float64:
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value = int64(v)
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case string:
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var err error
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if value, err = strconv.ParseInt(v, 10, 64); err != nil {
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return 0, err
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}
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default:
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return 0, fmt.Errorf("unable to convert %v to int64", number)
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}
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return value, nil
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}
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// ToFloat64 transform a given int into float64.
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func ToFloat64(number interface{}) (float64, error) {
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var value float64
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switch v := number.(type) {
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case int:
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value = float64(v)
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case int8:
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value = float64(v)
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case int16:
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value = float64(v)
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case int32:
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value = float64(v)
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case int64:
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value = float64(v)
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case uint:
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value = float64(v)
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case uint8:
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value = float64(v)
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case uint16:
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value = float64(v)
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case uint32:
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value = float64(v)
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case uint64:
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value = float64(v)
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case float32:
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value = float64(v)
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case float64:
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value = v
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case string:
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var err error
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if value, err = strconv.ParseFloat(v, 64); err != nil {
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return 0, err
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}
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default:
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return 0, fmt.Errorf("unable to convert %v to float64", number)
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}
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return value, nil
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}
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