init

.envrc

@@ -0,0 +1,3 @@
+source_url "https://raw.githubusercontent.com/cachix/devenv/82c0147677e510b247d8b9165c54f73d32dfd899/direnvrc" "sha256-7u4iDd1nZpxL4tCzmPG0dQgC5V+/44Ba+tHkPob1v2k="
+
+use devenv

.gitignore

@@ -0,0 +1,6 @@
+.devenv*
+devenv.local.nix
+
+.direnv
+
+.pre-commit-config.yaml

devenv.lock

@@ -0,0 +1,116 @@
+{
+  "nodes": {
+    "devenv": {
+      "locked": {
+        "dir": "src/modules",
+        "lastModified": 1732896163,
+        "owner": "cachix",
+        "repo": "devenv",
+        "rev": "2c928a199d56191d7a53f29ccafa56238c8ce4e5",
+        "type": "github"
+      },
+      "original": {
+        "dir": "src/modules",
+        "owner": "cachix",
+        "repo": "devenv",
+        "type": "github"
+      }
+    },
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1732722421,
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "9ed2ac151eada2306ca8c418ebd97807bb08f6ac",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "pre-commit-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1709087332,
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "637db329424fd7e46cf4185293b9cc8c88c95394",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1733212471,
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "55d15ad12a74eb7d4646254e13638ad0c4128776",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-stable": {
+      "locked": {
+        "lastModified": 1733220138,
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "bcb68885668cccec12276bbb379f8f2557aa06ce",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-24.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "pre-commit-hooks": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "gitignore": "gitignore",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "nixpkgs-stable": "nixpkgs-stable"
+      },
+      "locked": {
+        "lastModified": 1732021966,
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "3308484d1a443fc5bc92012435d79e80458fe43c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devenv": "devenv",
+        "nixpkgs": "nixpkgs",
+        "pre-commit-hooks": "pre-commit-hooks"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

devenv.nix

@@ -0,0 +1,3 @@
+{
+  languages.go.enable = true;
+}

devenv.yaml

@@ -0,0 +1,3 @@
+inputs:
+  nixpkgs:
+    url: github:NixOS/nixpkgs/nixos-unstable

go.mod

@@ -0,0 +1,3 @@
+module github.com/lukaswrz/gonfig
+
+go 1.23.3

gonfig.go

@@ -0,0 +1,74 @@
+// Package gonfig provides utilities for reading, unmarshaling, and validating
+// configuration files.
+package gonfig
+
+import (
+	"errors"
+	"fmt"
+	"os"
+)
+
+// Validator defines an interface for validating a configuration of type T. It
+// ensures that the provided configuration meets required constraints.
+type Validator[T any] interface {
+	// Validate checks the provided configuration and returns an error if it is
+	// invalid.
+	Validate(config T) []error
+}
+
+// ReadConfig reads a configuration file, unmarshals its content into the given
+// configuration object, and validates it using the provided validator. If the
+// primary path is empty, it searches for the configuration file in the
+// fallback paths. The function returns the resolved path to the configuration
+// file or a list of errors if the file cannot be located, read, unmarshaled,
+// or validated.
+func ReadConfig[T any](path string, paths []string, c *T, unmarshal func([]byte, *T) error, validator Validator[T]) (string, []error) {
+	var err error
+
+	path, err = findConfig(path, paths)
+	if err != nil {
+		return "", []error{err}
+	}
+
+	content, err := os.ReadFile(path)
+	if err != nil {
+		return "", []error{fmt.Errorf("unable to read configuration file %s: %w", path, err)}
+	}
+
+	err = unmarshal(content, c)
+	if err != nil {
+		return "", []error{fmt.Errorf("unable to unmarshal configuration file %s: %w", path, err)}
+	}
+
+	return path, validator.Validate(*c)
+}
+
+// findConfig determines the path to the configuration file by using the
+// provided primary path or searching through a list of fallback paths if the
+// primary path is empty. If no valid file is found, or if the specified file is
+// inaccessible, an error is returned.
+func findConfig(path string, paths []string) (string, error) {
+	var err error
+
+	if path == "" {
+		for _, p := range paths {
+			_, err = os.Stat(p)
+			if err != nil {
+				continue
+			}
+
+			path = p
+		}
+
+		if path == "" {
+			return "", errors.New("could not locate configuration file")
+		}
+	} else {
+		_, err = os.Stat(path)
+		if err != nil {
+			return "", fmt.Errorf("could not stat configuration file %s: %w", path, err)
+		}
+	}
+
+	return path, nil
+}