add project to version control

go.mod

@@ -0,0 +1,3 @@
+module github.com/xenomote/object_language
+
+go 1.19

main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/xenomote/object_language/pattern"
+)
+
+func main() {
+	p, err := pattern.Parse(`
+	{
+		"type": "event.source",
+		"data": {
+			"metadata": <=x> {
+				"set": null
+			}
+		}
+	}
+	`)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	b, err := p.Interpret(`
+	{
+		"type": "event.source",
+		"data": {
+			"metadata": {
+				"set": "null"
+			}
+		}
+	}
+	`)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	fmt.Println(b)
+}

pattern/array.go

@@ -0,0 +1,112 @@
+package pattern
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+func (a Array) Interpret(s string) (bindings map[string]string, err error) {
+	return a.Match(s, map[string]string{})
+}
+
+func (a Array) Match(s string, old_bindings map[string]string) (new_bindings map[string]string, err error) {
+	new_bindings = map[string]string{}
+
+	bindings := map[string]string{}
+	for k, v := range old_bindings {
+		bindings[k] = v
+	}
+
+	var input []json.RawMessage
+	err = json.Unmarshal([]byte(s), &input)
+	if err != nil {
+		input := "input"
+		if len(s) < 10 {
+			input = "\"" + s + "\""
+		}
+
+		return nil, fmt.Errorf("%s could not be interpreted as an array: %w", input, err)
+	}
+
+	for _, definition := range a.Definitions {
+		index, err := definition.Index.Index()
+		if err != nil {
+			return nil, err
+		}
+
+		prefix := ""
+		if definition.Index.String() != fmt.Sprint(index) {
+			prefix = definition.Index.String() + " = "
+		}
+
+		if index >= len(input) {
+			if definition.Optional {
+				continue
+			} else {
+				return nil, fmt.Errorf("array was not long enough to contain required index %s%d", prefix, index)
+			}
+		}
+
+		value := input[index]
+		matched_bindings, err := definition.Assignment.Match(string(value), bindings)
+		if err != nil {
+			return nil, fmt.Errorf("could not match index %s%d: %s", prefix, index, err)
+		}
+
+		for k, v := range matched_bindings {
+			if _, k_exists := bindings[k]; k_exists {
+				return nil, fmt.Errorf("binding for %s already exists and cannot be overwritten", k)
+			}
+
+			bindings[k] = v
+			new_bindings[k] = v
+		}
+	}
+
+	return new_bindings, nil
+}
+
+func (a Array) Validate(bindings map[string]bool) error {
+	indices := make(map[string]bool)
+	for _, d := range a.Definitions {
+		if _, exists := indices[d.Index.String()]; exists {
+			return fmt.Errorf("duplicate index %s", d.Index.String())
+		}
+
+		indices[d.Index.String()] = true
+	}
+
+	for _, d := range a.Definitions {
+		if err := d.Validate(bindings); err != nil {
+			return fmt.Errorf("at index %s: %s", d.Index, err)
+		}
+	}
+
+	return nil
+}
+
+func (a Array) String() string {
+	s := "["
+
+	for i, definition := range a.Definitions {
+		s += "\n" + indent(definition.String())
+
+		if i < len(a.Definitions)-1 {
+			s += ","
+		} else {
+			s += "\n"
+		}
+	}
+
+	s += "]"
+
+	return s
+}
+
+func (o ArrayDefinition) String() string {
+	op := ""
+	if o.Optional {
+		op = "?"
+	}
+	return o.Index.String() + op + ": " + o.Assignment.String()
+}

pattern/binding.go

@@ -0,0 +1,20 @@
+package pattern
+
+import "fmt"
+
+func (b Binding) Match(s string, bindings map[string]string) (map[string]string, error) {
+	return map[string]string{string(b): s}, nil
+}
+
+func (b Binding) Validate(bindings map[string]bool) error {
+	if _, exists := bindings[string(b)]; exists {
+		return fmt.Errorf("duplicate binding %s", b)
+	}
+
+	bindings[string(b)] = true
+	return nil
+}
+
+func (b Binding) String() string {
+	return "<=" + string(b) + ">"
+}