From 62ec09cc02549b8282681c3ebc676d9baa0414f6 Mon Sep 17 00:00:00 2001
From: Brad Stein <Brad.Stein@gmail.com>
Date: Sun, 11 Jan 2026 09:55:57 -0300
Subject: [PATCH] feat: add config builder and CLI command

---
 cmd/metis/config_cmd.go | 28 +++++++++++++
 cmd/metis/main.go       |  2 +
 pkg/config/config.go    | 89 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)
 create mode 100644 cmd/metis/config_cmd.go
 create mode 100644 pkg/config/config.go

diff --git a/cmd/metis/config_cmd.go b/cmd/metis/config_cmd.go
new file mode 100644
index 0000000..f998bfc
--- /dev/null
+++ b/cmd/metis/config_cmd.go
@@ -0,0 +1,28 @@
+package main
+
+import (
+    "encoding/json"
+    "flag"
+    "log"
+    "os"
+
+    "metis/pkg/config"
+)
+
+func configCmd(args []string) {
+    fs := flag.NewFlagSet("config", flag.ExitOnError)
+    invPath := fs.String("inventory", "inventory.yaml", "inventory file")
+    node := fs.String("node", "", "target node")
+    fs.Parse(args)
+    if *node == "" {
+        log.Fatalf("--node is required")
+    }
+    inv := loadInventory(*invPath)
+    cfg, err := config.Build(inv, *node)
+    if err != nil {
+        log.Fatalf("config build: %v", err)
+    }
+    enc := json.NewEncoder(os.Stdout)
+    enc.SetIndent("", "  ")
+    _ = enc.Encode(cfg)
+}
diff --git a/cmd/metis/main.go b/cmd/metis/main.go
index cd4b26b..a485faf 100644
--- a/cmd/metis/main.go
+++ b/cmd/metis/main.go
@@ -22,6 +22,8 @@ func main() {
 		planCmd(os.Args[2:])
 	case "burn":
 		burnCmd(os.Args[2:])
+	case "config":
+		configCmd(os.Args[2:])
 	default:
 		usage()
 		os.Exit(1)
diff --git a/pkg/config/config.go b/pkg/config/config.go
new file mode 100644
index 0000000..a8cbf99
--- /dev/null
+++ b/pkg/config/config.go
@@ -0,0 +1,89 @@
+package config
+
+import (
+    "fmt"
+
+    "metis/pkg/inventory"
+)
+
+// NodeConfig represents boot-time configuration to inject.
+type NodeConfig struct {
+    Hostname string            `json:"hostname"`
+    IP       string            `json:"ip"`
+    K3s      K3sConfig         `json:"k3s"`
+    SSHUser  string            `json:"ssh_user,omitempty"`
+    SSHKeys  []string          `json:"ssh_keys,omitempty"`
+    Labels   map[string]string `json:"labels,omitempty"`
+    Taints   []string          `json:"taints,omitempty"`
+    Fstab    []FstabEntry      `json:"fstab,omitempty"`
+}
+
+// K3sConfig includes role and token/url.
+type K3sConfig struct {
+    Role   string            `json:"role"`
+    URL    string            `json:"url,omitempty"`
+    Token  string            `json:"token,omitempty"`
+    Args   []string          `json:"args,omitempty"`
+    Labels map[string]string `json:"labels,omitempty"`
+    Taints []string          `json:"taints,omitempty"`
+}
+
+// FstabEntry for Longhorn or other mounts.
+type FstabEntry struct {
+    UUID       string `json:"uuid"`
+    Mountpoint string `json:"mountpoint"`
+    FS         string `json:"fs"`
+    Options    string `json:"options"`
+}
+
+// Build creates a NodeConfig from inventory.
+func Build(inv *inventory.Inventory, nodeName string) (*NodeConfig, error) {
+    n, cls, err := inv.FindNode(nodeName)
+    if err != nil {
+        return nil, err
+    }
+    labels := map[string]string{}
+    for k, v := range cls.DefaultLabels {
+        labels[k] = v
+    }
+    for k, v := range n.Labels {
+        labels[k] = v
+    }
+    taints := append([]string{}, cls.DefaultTaints...)
+    taints = append(taints, n.Taints...)
+
+    fstab := []FstabEntry{}
+    for _, d := range n.LonghornDisks {
+        fs := d.FS
+        if fs == "" {
+            fs = "ext4"
+        }
+        fstab = append(fstab, FstabEntry{
+            UUID:       d.UUID,
+            Mountpoint: d.Mountpoint,
+            FS:         fs,
+            Options:    "defaults,nofail",
+        })
+    }
+
+    cfg := &NodeConfig{
+        Hostname: n.Hostname,
+        IP:       n.IP,
+        SSHUser:  n.SSHUser,
+        SSHKeys:  n.SSHAuthorized,
+        Labels:   labels,
+        Taints:   taints,
+        Fstab:    fstab,
+        K3s: K3sConfig{
+            Role:   n.K3sRole,
+            URL:    n.K3sURL,
+            Token:  n.K3sToken,
+            Labels: labels,
+            Taints: taints,
+        },
+    }
+    if cfg.Hostname == "" || cfg.IP == "" {
+        return nil, fmt.Errorf("hostname/ip required for node %s", nodeName)
+    }
+    return cfg, nil
+}