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-rw-r--r--modules/templates/vars/vars.go92
1 files changed, 92 insertions, 0 deletions
diff --git a/modules/templates/vars/vars.go b/modules/templates/vars/vars.go
new file mode 100644
index 0000000..cc9d0e9
--- /dev/null
+++ b/modules/templates/vars/vars.go
@@ -0,0 +1,92 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package vars
+
+import (
+ "fmt"
+ "strings"
+ "unicode"
+ "unicode/utf8"
+)
+
+// ErrWrongSyntax represents a wrong syntax with a template
+type ErrWrongSyntax struct {
+ Template string
+}
+
+func (err ErrWrongSyntax) Error() string {
+ return fmt.Sprintf("wrong syntax found in %s", err.Template)
+}
+
+// ErrVarMissing represents an error that no matched variable
+type ErrVarMissing struct {
+ Template string
+ Var string
+}
+
+func (err ErrVarMissing) Error() string {
+ return fmt.Sprintf("the variable %s is missing for %s", err.Var, err.Template)
+}
+
+// Expand replaces all variables like {var} by `vars` map, it always returns the expanded string regardless of errors
+// if error occurs, the error part doesn't change and is returned as it is.
+func Expand(template string, vars map[string]string) (string, error) {
+ // in the future, if necessary, we can introduce some escape-char,
+ // for example: it will use `#' as a reversed char, templates will use `{#{}` to do escape and output char '{'.
+ var buf strings.Builder
+ var err error
+
+ posBegin := 0
+ strLen := len(template)
+ for posBegin < strLen {
+ // find the next `{`
+ pos := strings.IndexByte(template[posBegin:], '{')
+ if pos == -1 {
+ buf.WriteString(template[posBegin:])
+ break
+ }
+
+ // copy texts between vars
+ buf.WriteString(template[posBegin : posBegin+pos])
+
+ // find the var between `{` and `}`/end
+ posBegin += pos
+ posEnd := posBegin + 1
+ for posEnd < strLen {
+ if template[posEnd] == '}' {
+ posEnd++
+ break
+ } // in the future, if we need to support escape chars, we can do: if (isEscapeChar) { posEnd+=2 }
+ posEnd++
+ }
+
+ // the var part, it can be "{", "{}", "{..." or or "{...}"
+ part := template[posBegin:posEnd]
+ posBegin = posEnd
+ if part == "{}" || part[len(part)-1] != '}' {
+ // treat "{}" or "{..." as error
+ err = ErrWrongSyntax{Template: template}
+ buf.WriteString(part)
+ } else {
+ // now we get a valid key "{...}"
+ key := part[1 : len(part)-1]
+ keyFirst, _ := utf8.DecodeRuneInString(key)
+ if unicode.IsSpace(keyFirst) || unicode.IsPunct(keyFirst) || unicode.IsControl(keyFirst) {
+ // the if key doesn't start with a letter, then we do not treat it as a var now
+ buf.WriteString(part)
+ } else {
+ // look up in the map
+ if val, ok := vars[key]; ok {
+ buf.WriteString(val)
+ } else {
+ // write the non-existing var as it is
+ buf.WriteString(part)
+ err = ErrVarMissing{Template: template, Var: key}
+ }
+ }
+ }
+ }
+
+ return buf.String(), err
+}