Add custom backend configuration

internal/config/config.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
@@ -32,11 +33,29 @@ var (
 
 // Config is the on-disk YAML shape for application-level settings.
 type Config struct {
-	PromptDir  string         `yaml:"prompt_dir"`
-	ProfileDir string         `yaml:"profile_dir"`
-	SchemaDir  string         `yaml:"schema_dir"`
-	Server     ServerConfig   `yaml:"server"`
-	Defaults   DefaultsConfig `yaml:"defaults"`
+	PromptDir  string                   `yaml:"prompt_dir"`
+	ProfileDir string                   `yaml:"profile_dir"`
+	SchemaDir  string                   `yaml:"schema_dir"`
+	Server     ServerConfig             `yaml:"server"`
+	Defaults   DefaultsConfig           `yaml:"defaults"`
+	Backends   map[string]BackendConfig `yaml:"backends"`
+}
+
+type BackendConfig struct {
+	Endpoint         string         `yaml:"endpoint"`
+	APIKeyEnv        string         `yaml:"api_key_env"`
+	ExtraParams      map[string]any `yaml:"extra_params"`
+	ConcurrencyLimit int            `yaml:"concurrency_limit"`
+	QueueCapacity    *int           `yaml:"queue_capacity"`
+}
+
+type BackendSettings struct {
+	ID               string
+	Endpoint         string
+	APIKeyEnv        string
+	ExtraParams      map[string]any
+	ConcurrencyLimit int
+	QueueCapacity    *int
 }
 
 type ServerConfig struct {
@@ -62,6 +81,7 @@ type AppSettings struct {
 	MaxArtifactBytes    int64
 	MaxResponseBytes    int64
 	DefaultRenderFormat renderformat.PreparedRunOutputFormat
+	Backends            []BackendSettings
 }
 
 // CLIOverrides can be applied after config load to enforce precedence.
@@ -245,6 +265,25 @@ func applyConfig(base AppSettings, cfg Config) (AppSettings, error) {
 		}
 		out.DefaultRenderFormat = parsed
 	}
+	if len(cfg.Backends) > 0 {
+		ids := make([]string, 0, len(cfg.Backends))
+		for id := range cfg.Backends {
+			ids = append(ids, id)
+		}
+		sort.Strings(ids)
+		out.Backends = make([]BackendSettings, 0, len(ids))
+		for _, id := range ids {
+			backend := cfg.Backends[id]
+			out.Backends = append(out.Backends, BackendSettings{
+				ID:               id,
+				Endpoint:         backend.Endpoint,
+				APIKeyEnv:        backend.APIKeyEnv,
+				ExtraParams:      backend.ExtraParams,
+				ConcurrencyLimit: backend.ConcurrencyLimit,
+				QueueCapacity:    backend.QueueCapacity,
+			})
+		}
+	}
 
 	return out, nil
 }

internal/config/config_test.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
@@ -20,7 +21,7 @@ func TestLoadConfigMissingImplicitPathUsesBuiltInDefaults(t *testing.T) {
 	}
 
 	want := BuiltInDefaults()
-	if got != want {
+	if !reflect.DeepEqual(got, want) {
 		t.Fatalf("unexpected settings: got=%+v want=%+v", got, want)
 	}
 }
@@ -100,6 +101,78 @@ func TestLoadConfigAPIKeyFieldIsRejectedAsUnknown(t *testing.T) {
 	}
 }
 
+func TestLoadConfigBackendsRetainsResolvedSettingsInSortedOrder(t *testing.T) {
+	path := writeConfigFile(t, "config.yml", `
+backends:
+  zebra:
+    endpoint: https://zebra.example/v1
+    api_key_env: ZEBRA_API_KEY
+    extra_params:
+      provider_option: enabled
+      nested:
+        enabled: true
+        attempts: 2
+    concurrency_limit: 2
+  alpha:
+    endpoint: http://alpha.example/v1
+    queue_capacity: 0
+`)
+
+	got, err := LoadConfig(path, true)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if len(got.Backends) != 2 {
+		t.Fatalf("expected two backends, got %#v", got.Backends)
+	}
+	if got.Backends[0].ID != "alpha" || got.Backends[1].ID != "zebra" {
+		t.Fatalf("expected sorted backend IDs, got %#v", got.Backends)
+	}
+	if got.Backends[0].QueueCapacity == nil || *got.Backends[0].QueueCapacity != 0 {
+		t.Fatalf("expected explicit zero queue capacity, got %#v", got.Backends[0].QueueCapacity)
+	}
+	if got.Backends[1].QueueCapacity != nil {
+		t.Fatalf("expected omitted queue capacity to remain nil, got %#v", got.Backends[1].QueueCapacity)
+	}
+	wantParams := map[string]any{
+		"provider_option": "enabled",
+		"nested": map[string]any{
+			"enabled":  true,
+			"attempts": 2,
+		},
+	}
+	if !reflect.DeepEqual(got.Backends[1].ExtraParams, wantParams) {
+		t.Fatalf("unexpected extra params: got=%#v want=%#v", got.Backends[1].ExtraParams, wantParams)
+	}
+	if got.Backends[1].Endpoint != "https://zebra.example/v1" || got.Backends[1].APIKeyEnv != "ZEBRA_API_KEY" || got.Backends[1].ConcurrencyLimit != 2 {
+		t.Fatalf("unexpected zebra backend: %#v", got.Backends[1])
+	}
+}
+
+func TestLoadConfigRejectsUnknownOrSecretBackendFields(t *testing.T) {
+	for name, body := range map[string]string{
+		"unknown": "backends:\n  local:\n    endpoint: http://localhost:11434/v1\n    unexpected: value\n",
+		"secret":  "backends:\n  local:\n    endpoint: http://localhost:11434/v1\n    api_key: secret\n",
+	} {
+		t.Run(name, func(t *testing.T) {
+			path := writeConfigFile(t, "config.yml", body)
+			_, err := LoadConfig(path, true)
+			if !errors.Is(err, ErrInvalidConfigYAML) {
+				t.Fatalf("expected ErrInvalidConfigYAML, got %v", err)
+			}
+		})
+	}
+}
+
+func TestLoadConfigRejectsInvalidBackendFieldTypes(t *testing.T) {
+	path := writeConfigFile(t, "config.yml", "backends:\n  local:\n    endpoint: http://localhost:11434/v1\n    queue_capacity: not-a-number\n")
+
+	_, err := LoadConfig(path, true)
+	if !errors.Is(err, ErrInvalidConfigYAML) {
+		t.Fatalf("expected ErrInvalidConfigYAML, got %v", err)
+	}
+}
+
 func TestLoadConfigValidConfigSetsDirectoriesAndServerAddr(t *testing.T) {
 	path := writeConfigFile(t, "config.yml", `
 prompt_dir: ./prompts
@@ -196,7 +269,7 @@ func TestLoadConfigEmptyFileResolvesToBuiltInDefaults(t *testing.T) {
 	}
 
 	want := BuiltInDefaults()
-	if got != want {
+	if !reflect.DeepEqual(got, want) {
 		t.Fatalf("unexpected settings: got=%+v want=%+v", got, want)
 	}
 }