Add output directory configuration contract

internal/config/config.go

@@ -25,6 +25,7 @@ type Config struct {
 	WeatherAPI    WeatherAPIConfig        `yaml:"weather_api"`
 	Location      LocationConfig          `yaml:"location"`
 	Secrets       SecretsConfig           `yaml:"secrets"`
+	Output        OutputConfig            `yaml:"output"`
 	Notify        NotifyConfig            `yaml:"notify"`
 	MissingSource MissingSourceConfig     `yaml:"missing_source"`
 	Promptkit     PromptkitConfig         `yaml:"promptkit"`
@@ -51,6 +52,10 @@ type SecretsConfig struct {
 	Directory string `yaml:"directory"`
 }
 
+type OutputConfig struct {
+	Directory string `yaml:"directory"`
+}
+
 type NotifyConfig struct {
 	Distributor DistributorNotifyConfig `yaml:"distributor"`
 }

internal/config/config_test.go

@@ -4,6 +4,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -37,6 +38,9 @@ func TestDefaults(t *testing.T) {
 	if cfg.Secrets.Directory != "" {
 		t.Fatalf("Secrets.Directory = %q, want empty", cfg.Secrets.Directory)
 	}
+	if cfg.Output.Directory != "" {
+		t.Fatalf("Output.Directory = %q, want empty", cfg.Output.Directory)
+	}
 	if cfg.Notify.Distributor.Enabled {
 		t.Fatalf("Notify.Distributor.Enabled = true, want false")
 	}
@@ -78,6 +82,120 @@ func TestDefaults(t *testing.T) {
 	}
 }
 
+func TestOutputDirectoryLoading(t *testing.T) {
+	tests := []struct {
+		name      string
+		yaml      string
+		wantValue string
+		wantErr   string
+	}{
+		{
+			name:      "omitted",
+			yaml:      "{}\n",
+			wantValue: "",
+		},
+		{
+			name: "explicit empty",
+			yaml: `
+output:
+  directory: ""
+`,
+			wantValue: "",
+		},
+		{
+			name: "absolute path",
+			yaml: `
+output:
+  directory: /var/lib/weatherreporter/reports
+`,
+			wantValue: "/var/lib/weatherreporter/reports",
+		},
+		{
+			name: "relative path",
+			yaml: `
+output:
+  directory: reports/../published
+`,
+			wantValue: "reports/../published",
+		},
+		{
+			name: "whitespace only",
+			yaml: `
+output:
+  directory: "  \t  "
+`,
+			wantErr: "output.directory",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg, err := LoadFile(writeConfig(t, tt.yaml))
+			if tt.wantErr != "" {
+				if err == nil || !strings.Contains(err.Error(), tt.wantErr) {
+					t.Fatalf("LoadFile() error = %v, want %q", err, tt.wantErr)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("LoadFile() error = %v", err)
+			}
+			if cfg.Output.Directory != tt.wantValue {
+				t.Fatalf("Output.Directory = %q, want %q", cfg.Output.Directory, tt.wantValue)
+			}
+		})
+	}
+}
+
+func TestOutputDirectoryValidationIsConsistentForLoadedAndConstructedConfigs(t *testing.T) {
+	tests := []struct {
+		name      string
+		directory string
+		wantErr   string
+	}{
+		{name: "empty"},
+		{name: "absolute path", directory: "/var/lib/weatherreporter/reports"},
+		{name: "relative path", directory: "reports/../published"},
+		{name: "whitespace only", directory: " \t ", wantErr: "output.directory"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			yaml := "output:\n  directory: " + strconv.Quote(tt.directory) + "\n"
+			_, loadErr := LoadFile(writeConfig(t, yaml))
+
+			cfg := Defaults()
+			cfg.Output.Directory = tt.directory
+			validateErr := Validate(cfg)
+
+			if (loadErr == nil) != (validateErr == nil) {
+				t.Fatalf("LoadFile() error = %v, Validate() error = %v", loadErr, validateErr)
+			}
+			if tt.wantErr != "" {
+				if loadErr == nil || !strings.Contains(loadErr.Error(), tt.wantErr) {
+					t.Fatalf("LoadFile() error = %v, want %q", loadErr, tt.wantErr)
+				}
+				if validateErr == nil || !strings.Contains(validateErr.Error(), tt.wantErr) {
+					t.Fatalf("Validate() error = %v, want %q", validateErr, tt.wantErr)
+				}
+			}
+		})
+	}
+}
+
+func TestOutputDirectoryRejectsUnknownFields(t *testing.T) {
+	_, err := LoadFile(writeConfig(t, `
+output:
+  location: reports
+`))
+	if err == nil {
+		t.Fatal("LoadFile() error = nil, want strict decoding error")
+	}
+	if !strings.Contains(err.Error(), "field location not found") {
+		t.Fatalf("LoadFile() error = %q, want output field rejection", err.Error())
+	}
+}
+
 func TestLoadExampleConfig(t *testing.T) {
 	cfg, err := LoadFile(filepath.Join("..", "..", "examples", "config.yml"))
 	if err != nil {

internal/config/defaults.go

@@ -21,6 +21,9 @@ func Defaults() Config {
 		Secrets: SecretsConfig{
 			Directory: "",
 		},
+		Output: OutputConfig{
+			Directory: "",
+		},
 		Notify: NotifyConfig{
 			Distributor: DistributorNotifyConfig{
 				Enabled:                false,

internal/config/validate.go

@@ -15,6 +15,9 @@ func Validate(cfg Config) error {
 	if err := validateReportDistributorPathOverrides(cfg); err != nil {
 		return err
 	}
+	if cfg.Output.Directory != "" && strings.TrimSpace(cfg.Output.Directory) == "" {
+		return fmt.Errorf("output.directory must not be blank when configured")
+	}
 	if cfg.WeatherAPI.BaseURL != "" {
 		parsed, err := url.Parse(cfg.WeatherAPI.BaseURL)
 		if err != nil || parsed.Scheme == "" || parsed.Host == "" {