init

Author: gi8lino

README.md

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+# Resolver Package
+
+The `resolver` package provides a flexible and extensible way to resolve configuration values from various sources including environment variables, files, JSON, YAML, INI, and key-value files. It uses a prefix-based system to identify which resolver to use and returns the resolved value or an error if something goes wrong.
+
+## Installation
+
+```bash
+go get github.com/yourusername/yourrepo/resolver
+```
+
+## Usage
+
+The primary entry point is the `ResolveVariable` function. It takes a single string and attempts to resolve it based on its prefix:
+
+- `env`: – Resolves environment variables.
+  Example: `env:PATH` returns the value of the `PATH` environment variable.
+- `file`: – Resolves values from a simple key-value file.
+  Example: `file:/config/app.txt//KeyName` returns the value associated with `KeyName` in `app.txt`.
+- `json`: – Resolves values from a JSON file. Supports dot notation for nested keys.
+  Example: `json:/config/app.json//database.host` returns `host` field under `database` in `app.json`. It is also possible to indexing into arrays (e.g., `json:/config/app.json//servers.0.host`).
+- `yaml`: – Resolves values from a YAML file. Supports dot notation for nested keys.
+  Example: `yaml:/config/app.yaml//server.port` returns `port` under `server` in `app.yaml`.It is also possible to indexing into arrays (e.g., `yaml:/config/app.yaml//servers.0.host`).
+- `ini`: – Resolves values from an INI file. Can specify a section and key, or just a key in the default section.
+  Example: `ini:/config/app.ini//Section.Key` returns the value of `Key` under `Section`.
+- No prefix – Returns the value as-is, unchanged.
+
+## Example
+
+```go
+package main
+
+import (
+    "fmt"
+    "log"
+    "os"
+
+    "github.com/containeroo/portpatrol/resolver"
+)
+
+func main() {
+    os.Setenv("MY_VAR", "HelloWorld")
+
+    val, err := resolver.ResolveVariable("env:MY_VAR")
+    if err != nil {
+        log.Fatal(err)
+    }
+    fmt.Println(val) // Output: HelloWorld
+
+    // Resolve a JSON key:
+    // Given a JSON file: /config/app.json
+    // {
+    //   "server": {
+    //     "host": "localhost",
+    //     "port": 8080
+    //   }
+    // }
+    jsonVal, err := resolver.ResolveVariable("json:/config/app.json//server.host")
+    if err != nil {
+        log.Fatal(err)
+    }
+    fmt.Println(jsonVal) // Output: localhost
+}
+```

coverage.out

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+mode: set
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env.go

@@ -0,0 +1,18 @@
+package resolver
+
+import (
+	"fmt"
+	"os"
+)
+
+// EnvResolver resolves values using environment variables.
+// Usage: "env:MY_VAR" -> returns value of MY_VAR
+type EnvResolver struct{}
+
+func (r *EnvResolver) Resolve(value string) (string, error) {
+	res, found := os.LookupEnv(value)
+	if !found {
+		return "", fmt.Errorf("environment variable '%s' not found", value)
+	}
+	return res, nil
+}

env_test.go

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+package resolver
+
+import (
+	"os"
+	"testing"
+)
+
+func TestEnvResolver_Resolve(t *testing.T) {
+	resolver := &EnvResolver{}
+
+	os.Setenv("TEST_ENV_VAR", "test_value")
+	os.Setenv("EMPTY_ENV_VAR", "")
+
+	t.Run("Resolve existing environment variable", func(t *testing.T) {
+		val, err := resolver.Resolve("TEST_ENV_VAR")
+		if err != nil {
+			t.Errorf("unexpected error resolving 'TEST_ENV_VAR': %v", err)
+		}
+		if val != "test_value" {
+			t.Errorf("expected 'test_value' but got '%s'", val)
+		}
+	})
+
+	t.Run("Resolve empty environment variable", func(t *testing.T) {
+		val, err := resolver.Resolve("EMPTY_ENV_VAR")
+		if err != nil {
+			t.Errorf("unexpected error resolving 'EMPTY_ENV_VAR': %v", err)
+		}
+		if val != "" {
+			t.Errorf("expected '' (empty string) but got '%s'", val)
+		}
+	})
+
+	t.Run("Resolve missing environment variable", func(t *testing.T) {
+		_, err := resolver.Resolve("MISSING_ENV_VAR")
+		if err == nil {
+			t.Error("expected an error resolving 'MISSING_ENV_VAR', but got none")
+		}
+	})
+}

file.go

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+package resolver
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+// Resolves values from key = values files. The format can be:
+// "file:/config/app.txt//Key"
+// If no key is provided, returns the whole file.
+type KeyValueFileResolver struct{}
+
+func (f *KeyValueFileResolver) Resolve(value string) (string, error) {
+	filePath, keyPath := splitFileAndKey(value)
+	filePath = os.ExpandEnv(filePath)
+
+	file, err := os.Open(filePath)
+	if err != nil {
+		return "", fmt.Errorf("Failed to open file '%s'. %v", filePath, err)
+	}
+	defer file.Close()
+
+	if keyPath != "" {
+		return searchKeyInFile(file, keyPath)
+	}
+
+	// No key specified, read the whole file
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return "", fmt.Errorf("Failed to read file '%s'. %v", filePath, err)
+	}
+	return strings.TrimSpace(string(data)), nil
+}
+
+// searchKeyInFile searches for a specified key in a file and returns its associated value.
+func searchKeyInFile(file *os.File, key string) (string, error) {
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		pair := strings.SplitN(line, "=", 2)
+		if len(pair) == 2 && strings.TrimSpace(pair[0]) == key {
+			return strings.TrimSpace(pair[1]), nil
+		}
+	}
+	return "", fmt.Errorf("Key '%s' not found in file '%s'.", key, file.Name())
+}

file_test.go

@@ -0,0 +1,75 @@
+package resolver
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func createKeyValueTestFile(t *testing.T) string {
+	tempDir := t.TempDir()
+
+	testFilePath := filepath.Join(tempDir, "app.txt")
+	fileContent := `Key1 = Value1
+Key2=Value2
+Key with spaces =  TrimmedValue
+`
+	err := os.WriteFile(testFilePath, []byte(fileContent), 0666)
+	assert.NoError(t, err, "failed to create test file")
+
+	return testFilePath
+}
+
+func TestKeyValueFileResolver_Resolve(t *testing.T) {
+	t.Parallel()
+
+	resolver := &KeyValueFileResolver{}
+
+	t.Run("Resolve entire file", func(t *testing.T) {
+		t.Parallel()
+		testFilePath := createKeyValueTestFile(t)
+
+		val, err := resolver.Resolve(testFilePath)
+		assert.NoError(t, err, "unexpected error resolving entire file")
+
+		expected := "Key1 = Value1\nKey2=Value2\nKey with spaces =  TrimmedValue"
+		assert.Equal(t, expected, val)
+	})
+
+	t.Run("Resolve specific key", func(t *testing.T) {
+		t.Parallel()
+		testFilePath := createKeyValueTestFile(t)
+
+		val, err := resolver.Resolve(testFilePath + "//Key2")
+		assert.NoError(t, err, "unexpected error resolving specific key")
+		assert.Equal(t, "Value2", val)
+	})
+
+	t.Run("Resolve key with spaces", func(t *testing.T) {
+		t.Parallel()
+		testFilePath := createKeyValueTestFile(t)
+
+		val, err := resolver.Resolve(testFilePath + "//Key with spaces")
+		assert.NoError(t, err, "unexpected error resolving key with spaces")
+		assert.Equal(t, "TrimmedValue", val)
+	})
+
+	t.Run("Resolve missing key", func(t *testing.T) {
+		t.Parallel()
+		testFilePath := createKeyValueTestFile(t)
+
+		_, err := resolver.Resolve(testFilePath + "//NonExistentKey")
+		assert.Error(t, err, "expected an error resolving a missing key, but got none")
+	})
+
+	t.Run("Resolve non-existing file", func(t *testing.T) {
+		t.Parallel()
+		tempDir := t.TempDir()
+		nonExistentFile := filepath.Join(tempDir, "nonexistent.txt")
+
+		_, err := resolver.Resolve(nonExistentFile)
+		assert.Error(t, err, "expected an error resolving a non-existing file, but got none")
+	})
+}

ini.go

@@ -0,0 +1,54 @@
+package resolver
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"gopkg.in/ini.v1"
+)
+
+type INIResolver struct{}
+
+func (r *INIResolver) Resolve(value string) (string, error) {
+	filePath, keyPath := splitFileAndKey(value)
+	filePath = os.ExpandEnv(filePath)
+
+	cfg, err := ini.Load(filePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to read INI file '%s': %w", filePath, err)
+	}
+
+	if keyPath == "" {
+		// No key path means return the entire INI file
+		data, err := os.ReadFile(filePath)
+		if err != nil {
+			return "", fmt.Errorf("failed to read INI file '%s': %w", filePath, err)
+		}
+		return strings.TrimSpace(string(data)), nil
+	}
+
+	// KeyPath can be "Section.Key" or just "Key" (default section)
+	parts := strings.Split(keyPath, ".")
+	var sectionName, keyName string
+	if len(parts) == 1 {
+		// No explicit section, default section assumed
+		sectionName = "DEFAULT"
+		keyName = parts[0]
+	} else {
+		sectionName = parts[0]
+		keyName = strings.Join(parts[1:], ".")
+	}
+
+	section, err := cfg.GetSection(sectionName)
+	if err != nil {
+		return "", fmt.Errorf("section '%s' not found in INI '%s': %w", sectionName, filePath, err)
+	}
+
+	k := section.Key(keyName)
+	if k == nil || k.String() == "" {
+		return "", fmt.Errorf("key '%s' not found in section '%s' of INI '%s'", keyName, sectionName, filePath)
+	}
+
+	return k.String(), nil
+}