add processor to filter using expr expression

internal/processor/filter-expr.go

@@ -0,0 +1,59 @@
+package processor
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/vm"
+	"github.com/jwetzell/showbridge-go/internal/config"
+)
+
+// NOTE(jwetzell): see language definition https://expr-lang.org/docs/language-definition
+type FilterExpr struct {
+	config  config.ProcessorConfig
+	Program *vm.Program
+}
+
+func (se *FilterExpr) Process(ctx context.Context, payload any) (any, error) {
+
+	output, err := expr.Run(se.Program, payload)
+	if err != nil {
+		return nil, err
+	}
+
+	outputBool, ok := output.(bool)
+	if !ok {
+		return nil, fmt.Errorf("filter.expr expression did not return a boolean")
+	}
+	if !outputBool {
+		return nil, nil
+	}
+
+	return payload, nil
+}
+
+func (se *FilterExpr) Type() string {
+	return se.config.Type
+}
+
+func init() {
+	RegisterProcessor(ProcessorRegistration{
+		Type: "filter.expr",
+		New: func(config config.ProcessorConfig) (Processor, error) {
+			params := config.Params
+
+			expressionString, err := params.GetString("expression")
+			if err != nil {
+				return nil, fmt.Errorf("filter.expr expression error: %w", err)
+			}
+
+			program, err := expr.Compile(expressionString)
+			if err != nil {
+				return nil, err
+			}
+
+			return &FilterExpr{config: config, Program: program}, nil
+		},
+	})
+}

internal/processor/test/filter-expr_test.go

@@ -0,0 +1,176 @@
+package processor_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/jwetzell/showbridge-go/internal/config"
+	"github.com/jwetzell/showbridge-go/internal/processor"
+)
+
+func TestFilterExprFromRegistry(t *testing.T) {
+	registration, ok := processor.ProcessorRegistry["filter.expr"]
+	if !ok {
+		t.Fatalf("filter.expr processor not registered")
+	}
+
+	processorInstance, err := registration.New(config.ProcessorConfig{
+		Type: "filter.expr",
+		Params: map[string]any{
+			"expression": "foo + bar",
+		},
+	})
+	if err != nil {
+		t.Fatalf("failed to create filter.expr processor: %s", err)
+	}
+
+	if processorInstance.Type() != "filter.expr" {
+		t.Fatalf("filter.expr processor has wrong type: %s", processorInstance.Type())
+	}
+}
+
+func TestGoodFilterExpr(t *testing.T) {
+	tests := []struct {
+		name     string
+		params   map[string]any
+		payload  any
+		expected any
+	}{
+		{
+			name: "number",
+			params: map[string]any{
+				"expression": "Int > 0",
+			},
+			payload: TestStruct{
+				Int: 1,
+			},
+			expected: TestStruct{
+				Int: 1,
+			},
+		},
+		{
+			name: "string",
+			params: map[string]any{
+				"expression": "String == 'hello'",
+			},
+			payload: TestStruct{
+				String: "hello",
+			},
+			expected: TestStruct{
+				String: "hello",
+			},
+		},
+		{
+			name: "not matching",
+			params: map[string]any{
+				"expression": "Int > 0",
+			},
+			payload: TestStruct{
+				Int: 0,
+			},
+			expected: nil,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			registration, ok := processor.ProcessorRegistry["filter.expr"]
+			if !ok {
+				t.Fatalf("filter.expr processor not registered")
+			}
+
+			processorInstance, err := registration.New(config.ProcessorConfig{
+				Type:   "filter.expr",
+				Params: test.params,
+			})
+
+			if err != nil {
+				t.Fatalf("filter.expr failed to create processor: %s", err)
+			}
+
+			got, err := processorInstance.Process(t.Context(), test.payload)
+
+			if err != nil {
+				t.Fatalf("filter.expr failed: %s", err)
+			}
+
+			//TODO(jwetzell): work out better way to compare the any/any
+			if !reflect.DeepEqual(got, test.expected) {
+				t.Fatalf("filter.expr got %+v (%T), expected %+v (%T)", got, got, test.expected, test.expected)
+			}
+		})
+	}
+}
+
+func TestBadFilterExpr(t *testing.T) {
+	tests := []struct {
+		name        string
+		params      map[string]any
+		payload     any
+		errorString string
+	}{
+		{
+			name:   "no expression parameter",
+			params: map[string]any{
+				// no expression parameter
+			},
+			payload:     TestStruct{},
+			errorString: "filter.expr expression error: not found",
+		},
+		{
+			name: "non-string expression parameter",
+			params: map[string]any{
+				"expression": 12345,
+			},
+			payload:     TestStruct{},
+			errorString: "filter.expr expression error: not a string",
+		},
+		{
+			name: "invalid expression",
+			params: map[string]any{
+				"expression": "foo +",
+			},
+			payload:     TestStruct{},
+			errorString: "unexpected token EOF (1:5)\n | foo +\n | ....^",
+		},
+		{
+			name: "accessing missing field",
+			params: map[string]any{
+				"expression": "foo + bar",
+			},
+			payload: map[string]any{
+				"foo": 1,
+			},
+			errorString: "invalid operation: int + <nil> (1:5)\n | foo + bar\n | ....^",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			registration, ok := processor.ProcessorRegistry["filter.expr"]
+			if !ok {
+				t.Fatalf("filter.expr processor not registered")
+			}
+
+			processorInstance, err := registration.New(config.ProcessorConfig{
+				Type:   "filter.expr",
+				Params: test.params,
+			})
+			if err != nil {
+				if err.Error() != test.errorString {
+					t.Fatalf("filter.expr got error '%s', expected '%s'", err.Error(), test.errorString)
+				}
+				return
+			}
+			got, err := processorInstance.Process(t.Context(), test.payload)
+
+			if err == nil {
+				t.Fatalf("filter.expr expected to fail but succeeded, got: %v", got)
+
+			}
+			if err.Error() != test.errorString {
+				t.Fatalf("filter.expr got error '%s', expected '%s'", err.Error(), test.errorString)
+			}
+		})
+	}
+}