add toml support

Author: gi8lino

README.md

@@ -1,11 +1,11 @@
 # 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.
+The `resolver` package provides a flexible and extensible way to resolve configuration values from various sources including environment variables, files, `JSON`, `YAML`, `INI`, `TOML` 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
+go get github.com/containeroo/resolver/resolver
 ```
 
 ## Usage
@@ -22,6 +22,8 @@ The primary entry point is the `ResolveVariable` function. It takes a single str
   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`.
+- `toml`: – Resolves values from a TOML file.
+  Example: `toml:/config/app.toml//server.host` returns `host` under `server` in `app.toml`.
 - No prefix – Returns the value as-is, unchanged.
 
 ## Example
@@ -34,7 +36,7 @@ import (
     "log"
     "os"
 
-    "github.com/containeroo/portpatrol/resolver"
+    "github.com/containeroo/resolver"
 )
 
 func main() {

coverage.out

@@ -0,0 +1,15 @@
+module github.com/containeroo/resolver
+
+go 1.24.2
+
+require (
+	github.com/pelletier/go-toml/v2 v2.2.4
+	github.com/stretchr/testify v1.10.0
+	gopkg.in/ini.v1 v1.67.0
+	gopkg.in/yaml.v3 v3.0.1
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+)

go.mod

@@ -0,0 +1,14 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pelletier/go-toml/v2 v2.2.4 h1:mye9XuhQ6gvn5h28+VilKrrPoQVanw5PMw/TB0t5Ec4=
+github.com/pelletier/go-toml/v2 v2.2.4/go.mod h1:2gIqNv+qfxSVS7cM2xJQKtLSTLUE9V8t9Stt+h56mCY=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
+gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

go.sum

@@ -12,11 +12,12 @@ type Resolver interface {
 
 // Prefixes for different resolvers
 const (
-	envPrefix  = "env:"
-	jsonPrefix = "json:"
-	yamlPrefix = "yaml:"
-	iniPrefix  = "ini:"
-	filePrefix = "file:"
+	envPrefix  string = "env:"
+	filePrefix string = "file:"
+	iniPrefix  string = "ini:"
+	jsonPrefix string = "json:"
+	tomlPrefix string = "toml:"
+	yamlPrefix string = "yaml:"
 )
 
 // Global registry of resolvers
@@ -26,6 +27,7 @@ var resolvers = map[string]Resolver{
 	yamlPrefix: &YAMLResolver{},
 	iniPrefix:  &INIResolver{},
 	filePrefix: &INIResolver{},
+	tomlPrefix: &TOMLResolver{},
 }
 
 // ResolveVariable attempts to resolve the given value by checking for known prefixes.

resolver.go

@@ -0,0 +1,62 @@
+package resolver
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/pelletier/go-toml/v2"
+)
+
+// Resolves a value by loading a TOML file and extracting a nested key.
+// The value after the prefix should be in the format "path/to/file.toml//key1.key2.keyN"
+// If no key is provided, returns the entire TOML file as a string.
+// Example:
+// "toml:/config/app.toml//server.host"
+// would load app.toml, parse it as TOML, and then return the value at server.host.
+//
+// Keys are navigated via dot notation.
+// If no key is provided (no "//" present), returns the entire TOML file as string.
+type TOMLResolver struct{}
+
+func (r *TOMLResolver) Resolve(value string) (string, error) {
+	filePath, keyPath := splitFileAndKey(value)
+	filePath = os.ExpandEnv(filePath)
+
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to read TOML file '%s': %w", filePath, err)
+	}
+
+	// Validate TOML syntax by decoding into a dummy struct
+	var validationTarget struct{}
+	if err := toml.Unmarshal(data, &validationTarget); err != nil {
+		return "", fmt.Errorf("failed to parse TOML in '%s': %w", filePath, err)
+	}
+
+	// Decode into navigable structure
+	var content map[string]any
+	if err := toml.Unmarshal(data, &content); err != nil {
+		return "", fmt.Errorf("failed to parse TOML in '%s': %w", filePath, err)
+	}
+
+	if keyPath == "" {
+		return strings.TrimSpace(string(data)), nil
+	}
+
+	val, err := navigateData(content, strings.Split(keyPath, "."))
+	if err != nil {
+		return "", fmt.Errorf("key path '%s' not found in TOML '%s': %w", keyPath, filePath, err)
+	}
+
+	if strVal, ok := val.(string); ok {
+		return strVal, nil
+	}
+
+	tomlVal, err := toml.Marshal(val)
+	if err != nil {
+		return "", fmt.Errorf("failed to encode TOML value: %w", err)
+	}
+
+	return strings.TrimSpace(string(tomlVal)), nil
+}

toml.go

@@ -0,0 +1,154 @@
+package resolver
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func createTomlTestFile(t *testing.T) string {
+	t.Helper()
+
+	tempDir := t.TempDir()
+	testFilePath := filepath.Join(tempDir, "config.toml")
+
+	fileContent := `emptyString = ""
+
+[server]
+host = "localhost"
+port = 8080
+[server.nested]
+key = "value"
+
+[[servers]]
+host = "example.com"
+port = 80
+
+[[servers]]
+host = "example.org"
+port = 443
+
+[nonString]
+inner = true
+`
+
+	err := os.WriteFile(testFilePath, []byte(fileContent), 0666)
+	assert.NoError(t, err, "failed to create test TOML file")
+
+	return testFilePath
+}
+
+func TestTOMLResolver_Resolve(t *testing.T) {
+	t.Parallel()
+	resolver := &TOMLResolver{}
+
+	t.Run("Resolve entire file", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		val, err := resolver.Resolve(testFilePath)
+		assert.NoError(t, err, "unexpected error resolving entire TOML file")
+
+		expected := `emptyString = ""
+
+[server]
+host = "localhost"
+port = 8080
+[server.nested]
+key = "value"
+
+[[servers]]
+host = "example.com"
+port = 80
+
+[[servers]]
+host = "example.org"
+port = 443
+
+[nonString]
+inner = true`
+		assert.Equal(t, expected, val)
+	})
+
+	t.Run("Resolve top-level key", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		val, err := resolver.Resolve(testFilePath + "//server.host")
+		assert.NoError(t, err, "unexpected error resolving top-level key")
+		assert.Equal(t, "localhost", val)
+	})
+
+	t.Run("Resolve nested key", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		val, err := resolver.Resolve(testFilePath + "//server.nested.key")
+		assert.NoError(t, err, "unexpected error resolving nested key")
+		assert.Equal(t, "value", val)
+	})
+
+	t.Run("Resolve array element", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		val, err := resolver.Resolve(testFilePath + "//servers.1.host")
+		assert.NoError(t, err, "unexpected error resolving array element")
+		assert.Equal(t, "example.org", val)
+	})
+
+	t.Run("Resolve empty string key", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		val, err := resolver.Resolve(testFilePath + "//emptyString")
+		assert.NoError(t, err, "unexpected error resolving empty string key")
+		assert.Equal(t, "", val)
+	})
+
+	t.Run("Resolve non-string value", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		val, err := resolver.Resolve(testFilePath + "//nonString")
+		assert.NoError(t, err, "unexpected error resolving non-string value")
+
+		expected := `inner = true`
+		assert.Equal(t, expected, val)
+	})
+
+	t.Run("Resolve missing key", func(t *testing.T) {
+		t.Parallel()
+
+		testFilePath := createTomlTestFile(t)
+		_, err := resolver.Resolve(testFilePath + "//server.missing")
+		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.toml")
+
+		_, err := resolver.Resolve(nonExistentFile)
+		assert.Error(t, err, "expected an error resolving a non-existing file, but got none")
+	})
+
+	t.Run("Invalid TOML", func(t *testing.T) {
+		t.Parallel()
+
+		tempDir := t.TempDir()
+		testFilePath := filepath.Join(tempDir, "bad.toml")
+
+		invalid := "= invalid"
+		err := os.WriteFile(testFilePath, []byte(invalid), 0666)
+		assert.NoError(t, err)
+
+		result, err := resolver.Resolve(testFilePath)
+		assert.Equal(t, "", result)
+		assert.Error(t, err, "expected parse error but got none")
+	})
+}