Feat v0.8.2 capability negotiation (#69)

Co-authored-by: Jeffrey Smith <jasafpro@gmail.com>
Co-committed-by: Jeffrey Smith <jasafpro@gmail.com>

server/handlers/capabilities.go

@@ -0,0 +1,146 @@
+package handlers
+
+import (
+	"context"
+	"database/sql"
+	"log"
+
+	"github.com/gin-gonic/gin"
+
+	"armature/storage"
+)
+
+// ── Capability detection ────────────────────────────────────────────
+
+// DetectCapabilities probes the runtime environment and returns a map
+// of capability name → available.  Called once at startup and again on
+// each admin GET /capabilities request.
+func DetectCapabilities(db *sql.DB, isPostgres bool, objStore storage.ObjectStore, workspaceRoot string) map[string]bool {
+	caps := map[string]bool{
+		"postgres":       false,
+		"pgvector":       false,
+		"object_storage": false,
+		"s3":             false,
+		"workspace":      false,
+	}
+
+	// postgres: dialect check
+	if isPostgres {
+		caps["postgres"] = true
+	}
+
+	// pgvector: query pg_extension (PG only)
+	if isPostgres && db != nil {
+		var one int
+		err := db.QueryRow("SELECT 1 FROM pg_extension WHERE extname = 'vector'").Scan(&one)
+		caps["pgvector"] = err == nil
+	}
+
+	// object_storage: configured and healthy
+	if objStore != nil {
+		if err := objStore.Healthy(context.Background()); err == nil {
+			caps["object_storage"] = true
+		}
+	}
+
+	// s3: specific backend check
+	if objStore != nil && objStore.Backend() == "s3" {
+		caps["s3"] = true
+	}
+
+	// workspace: root exists and is writable
+	if workspaceRoot != "" && storage.IsPathWritable(workspaceRoot) {
+		caps["workspace"] = true
+	}
+
+	return caps
+}
+
+// ── Manifest parsing ────────────────────────────────────────────────
+
+// Capabilities holds the parsed capabilities block from a package manifest.
+type Capabilities struct {
+	Required []string
+	Optional []string
+}
+
+// ParseCapabilities extracts capabilities.required and capabilities.optional
+// from a manifest map.  Returns zero value + false if no capabilities block.
+func ParseCapabilities(manifest map[string]any) (Capabilities, bool) {
+	capsRaw, ok := manifest["capabilities"].(map[string]any)
+	if !ok {
+		return Capabilities{}, false
+	}
+
+	var caps Capabilities
+	if req, ok := capsRaw["required"].([]any); ok {
+		for _, v := range req {
+			if s, ok := v.(string); ok && s != "" {
+				caps.Required = append(caps.Required, s)
+			}
+		}
+	}
+	if opt, ok := capsRaw["optional"].([]any); ok {
+		for _, v := range opt {
+			if s, ok := v.(string); ok && s != "" {
+				caps.Optional = append(caps.Optional, s)
+			}
+		}
+	}
+
+	return caps, true
+}
+
+// CheckRequiredCapabilities returns the subset of required capabilities
+// that are not present in the detected set.
+func CheckRequiredCapabilities(required []string, detected map[string]bool) []string {
+	var missing []string
+	for _, r := range required {
+		if !detected[r] {
+			missing = append(missing, r)
+		}
+	}
+	return missing
+}
+
+// capabilityHelpText returns operator-facing remediation hints keyed by
+// capability name.
+func capabilityHelpText(missing []string) map[string]string {
+	hints := map[string]string{
+		"postgres":       "Switch DB_DRIVER to postgres and configure DATABASE_URL.",
+		"pgvector":       "Run `CREATE EXTENSION vector;` in your PostgreSQL database.",
+		"object_storage": "Configure STORAGE_BACKEND (pvc or s3) and ensure the backend is healthy.",
+		"s3":             "Set STORAGE_BACKEND=s3 and configure S3_ENDPOINT, S3_BUCKET, S3_ACCESS_KEY, S3_SECRET_KEY.",
+		"workspace":      "Set WORKSPACE_ROOT to a writable directory path.",
+	}
+	result := make(map[string]string, len(missing))
+	for _, m := range missing {
+		if h, ok := hints[m]; ok {
+			result[m] = h
+		} else {
+			result[m] = "Unknown capability — check package documentation."
+		}
+	}
+	return result
+}
+
+// ── Admin endpoint ──────────────────────────────────────────────────
+
+// CapabilitiesHandler serves the admin capabilities endpoint.
+type CapabilitiesHandler struct {
+	detect func() map[string]bool
+}
+
+// NewCapabilitiesHandler creates a handler that re-probes capabilities on
+// each request so the response reflects current state.
+func NewCapabilitiesHandler(detect func() map[string]bool) *CapabilitiesHandler {
+	return &CapabilitiesHandler{detect: detect}
+}
+
+// GetCapabilities returns detected environment capabilities.
+// GET /api/v1/admin/capabilities
+func (h *CapabilitiesHandler) GetCapabilities(c *gin.Context) {
+	caps := h.detect()
+	log.Printf("[capabilities] probed: %v", caps)
+	c.JSON(200, caps)
+}