Allow force-exit program through context

Signed-off-by: Knut Ahlers <knut@ahlers.me>

intcode.go

@@ -1,6 +1,7 @@
 package aoc2019
 
 import (
+	"context"
 	"log"
 	"reflect"
 	"strconv"
@@ -91,24 +92,45 @@ func parseIntcode(code string) ([]int64, error) {
 	return out, nil
 }
 
+type intcodeParams struct {
+	// Intcode program to execute
+	Code []int64
+	// Context to execute the program in (program might hang on input if context is closed during input directive)
+	Context context.Context
+	// Channel / Callback to query on input directive
+	In interface{}
+	// Channel to use for output directive
+	Out chan int64
+}
+
 func executeIntcode(code []int64, in interface{}, out chan int64) ([]int64, error) {
+	return executeIntcodeWithParams(intcodeParams{
+		Code:    code,
+		Context: context.Background(),
+		In:      in,
+		Out:     out,
+	})
+}
+
+func executeIntcodeWithParams(params intcodeParams) ([]int64, error) {
 	var (
+		code         = params.Code
 		inCB         func() (int64, error)
 		pos          int64
 		relativeBase int64
 	)
 
-	if out != nil {
-		defer close(out)
+	if params.Out != nil {
+		defer close(params.Out)
 	}
 
-	switch in.(type) {
+	switch params.In.(type) {
 	case nil:
 		inCB = func() (int64, error) { return 0, errors.New("No input available") }
 	case chan int64:
-		inCB = func() (int64, error) { return <-(in.(chan int64)), nil }
+		inCB = func() (int64, error) { return <-(params.In.(chan int64)), nil }
 	case func() (int64, error):
-		inCB = in.(func() (int64, error))
+		inCB = params.In.(func() (int64, error))
 	default:
 		return nil, errors.New("Unsupported input type")
 	}
@@ -169,6 +191,10 @@ func executeIntcode(code []int64, in interface{}, out chan int64) ([]int64, erro
 			return nil, errors.Errorf("Code position out of bounds: %d (len=%d)", pos, len(code))
 		}
 
+		if err := params.Context.Err(); err != nil {
+			return nil, errors.Wrap(err, "Context closed")
+		}
+
 		// Position is expected to be an OpCode
 		op := parseOpCode(code[pos])
 
@@ -195,7 +221,7 @@ func executeIntcode(code []int64, in interface{}, out chan int64) ([]int64, erro
 			pos += 2
 
 		case opCodeTypeOutput: // p1 => out
-			out <- getParamValue(1, op)
+			params.Out <- getParamValue(1, op)
 			pos += 2
 
 		case opCodeTypeJumpIfTrue: // p1 != 0 => jmp