package lang

import (
	"fmt"
	"regexp"
	"strconv"
)

type DiagnosticSeverity int

const (
	DiagnosticError   DiagnosticSeverity = 1
	DiagnosticWarning DiagnosticSeverity = 2
)

type SourceSpan struct {
	Start int
	End   int
}

type SemanticDiagnostic struct {
	Code     string
	Message  string
	Severity DiagnosticSeverity
	Span     SourceSpan
}

func (diagnostic SemanticDiagnostic) Error() string { return diagnostic.Message }

var semanticOffsetPattern = regexp.MustCompile(`\sat\s(\d+)$`)

func diagnosticForError(code string, err error) SemanticDiagnostic {
	span := SourceSpan{}
	if match := semanticOffsetPattern.FindStringSubmatch(err.Error()); len(match) == 2 {
		if offset, parseErr := strconv.Atoi(match[1]); parseErr == nil {
			span = SourceSpan{Start: offset, End: offset + 1}
		}
	}
	return SemanticDiagnostic{Code: code, Message: err.Error(), Severity: DiagnosticError, Span: span}
}

func undefinedDiagnostic(name string, position int) SemanticDiagnostic {
	end := position + len(name)
	return SemanticDiagnostic{
		Code:     "undefined-symbol",
		Message:  fmt.Sprintf("undefined identifier %s", name),
		Severity: DiagnosticError,
		Span:     SourceSpan{Start: position, End: end},
	}
}