mirror of https://github.com/perkeep/perkeep.git
105 lines
2.5 KiB
Go
105 lines
2.5 KiB
Go
/*
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Copyright 2011 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package jsonconfig
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import (
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"os"
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"fmt"
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"regexp"
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)
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var envPattern = regexp.MustCompile(`\$\{[A-Za-z0-9_]+\}`)
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func EvaluateExpressions(m map[string]interface{}) os.Error {
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for k, ei := range m {
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switch subval := ei.(type) {
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case string:
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continue
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case bool:
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continue
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case float64:
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continue
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case []interface{}:
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if len(subval) == 0 {
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continue
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}
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var expander func(v []interface{}) (interface{}, os.Error)
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if firstString, ok := subval[0].(string); ok {
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switch firstString {
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case "_env":
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expander = expandEnv
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case "_file":
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expander = expandFile
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}
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}
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if expander != nil {
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newval, err := expander(subval[1:])
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if err != nil {
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return err
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}
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m[k] = newval
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}
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case map[string]interface{}:
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if err := EvaluateExpressions(subval); err != nil {
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return err
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}
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default:
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return fmt.Errorf("Unhandled type %T", ei)
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}
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}
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return nil
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}
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// Permit either:
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// ["_env", "VARIABLE"] (required to be set)
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// or ["_env", "VARIABLE", "default_value"]
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func expandEnv(v []interface{}) (interface{}, os.Error) {
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hasDefault := false
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def := ""
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if len(v) < 1 || len(v) > 2 {
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return "", fmt.Errorf("_env expansion expected 1 or 2 args, got %d", len(v))
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}
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s, ok := v[0].(string)
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if !ok {
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return "", fmt.Errorf("Expected a string after _env expansion; got %#v", v[0])
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}
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if len(v) == 2 {
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hasDefault = true
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def, hasDefault = v[1].(string)
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if !hasDefault {
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return "", fmt.Errorf("Expected default value in %q _env expansion; got %#v", s, v[1])
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}
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}
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var err os.Error
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expanded := envPattern.ReplaceAllStringFunc(s, func(match string) string {
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envVar := match[2 : len(match)-1]
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val := os.Getenv(envVar)
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if val == "" {
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if hasDefault {
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return def
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}
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err = fmt.Errorf("couldn't expand environment variable %q", envVar)
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}
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return val
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})
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return expanded, err
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}
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func expandFile(v []interface{}) (interface{}, os.Error) {
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return "", os.NewError("_file not implemented")
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}
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