initial version of the flake-info command

A tool to display information about a flake. For now we shows all the
inputs and when they were updated last.

3 files changed, 139 insertions, 0 deletions

diff --git a/cmd/flake-info/main.go b/cmd/flake-info/main.go
new file mode 100644
index 0000000..d41f321
--- /dev/null
+++ b/cmd/flake-info/main.go
@@ -0,0 +1,43 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/fcuny/world/pkg/flake/lock"
+)
+
+func main() {
+	var flakeLockPath string
+
+	flag.StringVar(&flakeLockPath, "flake-lock", "flake.lock", "path to the flake lock file")
+
+	flag.Parse()
+
+	if _, err := os.Stat(flakeLockPath); err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			fmt.Fprintf(os.Stderr, "%s does not exists\n", flakeLockPath)
+		} else {
+			fmt.Fprintf(os.Stderr, "failed to check if %s exists: %v\n", flakeLockPath, err)
+		}
+		os.Exit(1)
+	}
+
+	lock, err := lock.New(flakeLockPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to parse the lockfile for %s: %+v\n", flakeLockPath, err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("%s info:\n", flakeLockPath)
+	fmt.Printf("version: %d\n", lock.Version)
+	fmt.Printf("all nodes:\n")
+	for nodeName, node := range lock.Nodes {
+		date := time.Unix(node.Locked.LastModified, 0)
+		unitTimeInRFC3339 := date.Format(time.RFC3339)
+		fmt.Printf("- %s was updated on %s\n", nodeName, unitTimeInRFC3339)
+	}
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..c28fd3c
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/fcuny/world
+
+go 1.21.4
diff --git a/pkg/flake/lock/main.go b/pkg/flake/lock/main.go
new file mode 100644
index 0000000..0fa21f4
--- /dev/null
+++ b/pkg/flake/lock/main.go
@@ -0,0 +1,93 @@
+package lock
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+type FlakeLock struct {
+	// Version of the lock file
+	Version int
+	// Root is the root node for the flake, containing all the inputs
+	Root RootNode
+	// Nodes represent all the inputs node for a flake
+	Nodes map[string]Node
+}
+
+type Node struct {
+	// Flake indicate whether the input is a flake
+	Flake bool `json:"flake"`
+	// Locked represent the locked attribute of the input
+	Locked repoLocked `json:"locked"`
+	// Original represent the user supplied attributes for the input
+	Original repoOriginal `json:"original"`
+}
+
+type repoLocked struct {
+	// LastModified represent the timestamp of when the input was updated last
+	LastModified int64 `json:"lastModified"`
+	// NarHash is the NAR hash for the input
+	NarHash string `json:"narHash"`
+	// Owner of the repository
+	Owner string `json:"owner"`
+	// Repository of the input
+	Repo string `json:"repo"`
+	// Revision of the input
+	Rev string `json:"rev"`
+	// Type of input
+	Type string `json:"type"`
+}
+
+type repoOriginal struct {
+	Owner string `json:"owner"`
+	Ref   string `json:"ref"`
+	Repo  string `json:"repo"`
+	Type  string `json:"type"`
+}
+
+// RootNode is a mapping of input
+type RootNode struct {
+	// Inputs contains the mapping of input
+	Inputs map[string]string `json:"inputs"`
+}
+
+// New return a representation of a flake lock
+func New(flakeLockPath string) (*FlakeLock, error) {
+	content, err := os.ReadFile(flakeLockPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read %s: %v", flakeLockPath, err)
+	}
+
+	var lock struct {
+		Version int                        `json:"version"`
+		Root    string                     `json:"root"`
+		Nodes   map[string]json.RawMessage `json:"nodes"`
+	}
+
+	if err := json.Unmarshal(content, &lock); err != nil {
+		return nil, fmt.Errorf("failed to parse %s: %v", flakeLockPath, err)
+	}
+
+	var flakeLock FlakeLock
+	flakeLock.Version = lock.Version
+	flakeLock.Nodes = map[string]Node{}
+
+	for nodeName, node := range lock.Nodes {
+		if nodeName != lock.Root {
+			var n Node
+			if err := json.Unmarshal(node, &n); err != nil {
+				return nil, fmt.Errorf("failed to read node %s: %v", nodeName, err)
+			}
+			flakeLock.Nodes[nodeName] = n
+		} else {
+			var r RootNode
+			if err := json.Unmarshal(node, &r); err != nil {
+				return nil, fmt.Errorf("failed to read the root node: %v", err)
+			}
+			flakeLock.Root = r
+		}
+	}
+
+	return &flakeLock, nil
+}