Implemented extern functions

src/scanner/scanFunctionSignature.go

@@ -0,0 +1,125 @@
+package scanner
+
+import (
+	"git.akyoto.dev/cli/q/src/core"
+	"git.akyoto.dev/cli/q/src/errors"
+	"git.akyoto.dev/cli/q/src/fs"
+	"git.akyoto.dev/cli/q/src/token"
+)
+
+// scanFunctionSignature scans a function declaration without the body.
+func scanFunctionSignature(file *fs.File, tokens token.List, i int, delimiter token.Kind) (*core.Function, int, error) {
+	var (
+		groupLevel  = 0
+		nameStart   = i
+		paramsStart = -1
+		paramsEnd   = -1
+		typeStart   = -1
+		typeEnd     = -1
+	)
+
+	i++
+
+	// Function parameters
+	for i < len(tokens) {
+		if tokens[i].Kind == token.GroupStart {
+			groupLevel++
+			i++
+
+			if groupLevel == 1 {
+				paramsStart = i
+			}
+
+			continue
+		}
+
+		if tokens[i].Kind == token.GroupEnd {
+			groupLevel--
+
+			if groupLevel < 0 {
+				return nil, i, errors.New(errors.MissingGroupStart, file, tokens[i].Position)
+			}
+
+			if groupLevel == 0 {
+				paramsEnd = i
+				i++
+				break
+			}
+
+			i++
+			continue
+		}
+
+		if tokens[i].Kind == token.Invalid {
+			return nil, i, errors.New(&errors.InvalidCharacter{Character: tokens[i].Text(file.Bytes)}, file, tokens[i].Position)
+		}
+
+		if tokens[i].Kind == token.EOF {
+			if groupLevel > 0 {
+				return nil, i, errors.New(errors.MissingGroupEnd, file, tokens[i].Position)
+			}
+
+			if paramsStart == -1 {
+				return nil, i, errors.New(errors.ExpectedFunctionParameters, file, tokens[i].Position)
+			}
+
+			return nil, i, nil
+		}
+
+		if groupLevel > 0 {
+			i++
+			continue
+		}
+
+		return nil, i, errors.New(errors.ExpectedFunctionParameters, file, tokens[i].Position)
+	}
+
+	// Return type
+	if i < len(tokens) && tokens[i].Kind == token.ReturnType {
+		typeStart = i + 1
+
+		for i < len(tokens) && tokens[i].Kind != delimiter {
+			i++
+		}
+
+		typeEnd = i
+	}
+
+	name := tokens[nameStart].Text(file.Bytes)
+	function := core.NewFunction(file.Package, name, file, nil)
+
+	if typeStart != -1 {
+		if tokens[typeStart].Kind == token.GroupStart && tokens[typeEnd-1].Kind == token.GroupEnd {
+			typeStart++
+			typeEnd--
+		}
+
+		outputTokens := tokens[typeStart:typeEnd]
+
+		err := outputTokens.Split(func(tokens token.List) error {
+			function.Output = append(function.Output, core.NewOutput(tokens))
+			return nil
+		})
+
+		if err != nil {
+			return nil, i, err
+		}
+	}
+
+	parameters := tokens[paramsStart:paramsEnd]
+
+	err := parameters.Split(func(tokens token.List) error {
+		if len(tokens) == 0 {
+			return errors.New(errors.MissingParameter, file, parameters[0].Position)
+		}
+
+		if len(tokens) == 1 {
+			return errors.New(errors.MissingType, file, tokens[0].End())
+		}
+
+		function.Input = append(function.Input, core.NewInput(tokens))
+		return nil
+	})
+
+	return function, i, err
+}