package engine

func selectOptions[T any](source Source, supplied []Options[T]) (Options[T], []Diagnostic) {
	if len(supplied) > 1 {
		return Options[T]{}, []Diagnostic{optionDiagnostic(CodeOptionsInvalid, "Load accepts at most one options value")}
	}
	var options Options[T]
	if len(supplied) == 1 {
		options = supplied[0]
	}
	var diagnostics []Diagnostic
	definition := options.Definition
	if !validOverlayName(options.Overlay) {
		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "overlay name must contain only ASCII letters, digits, underscore, or hyphen"))
	}
	if options.Filesystem != nil {
		diagnostics = append(diagnostics, filesystemOptionDiagnostics(source, options.Filesystem)...)
	}
	if source.kind == sourceNone && options.Imports {
		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "NoSource cannot enable imports"))
	}
	if source.kind == sourceNone && options.Overlay != "" && options.Overlay != "default" {
		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "NoSource cannot select an active overlay"))
	}
	if options.Filesystem == nil && (source.kind == sourceBytes || source.kind == sourceReader || source.kind == sourceMapping) && (options.Imports || activeOverlay(options.Overlay)) {
		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "synthetic-source imports or overlays require filesystem context"))
	}
	if definition.Version != nil {
		if !definition.Version.Path.valid() {
			diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "schema-version path is invalid"))
		}
		if definition.Version.Check == nil {
			diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "schema-version rule requires a checker"))
		}
	}
	if options.SourceVersionMode != sourceVersionModeDefault && options.SourceVersionMode != sourceVersionModeIfPresent && options.SourceVersionMode != sourceVersionModeRequired {
		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "source-version mode is invalid"))
	} else if options.SourceVersionMode != sourceVersionModeDefault && (definition.Version == nil || !definition.Version.Path.valid() || definition.Version.Check == nil) {
		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "source-version checking requires a valid version rule and checker"))
	}
	return options, canonicalDiagnostics(diagnostics)
}

func optionDiagnostic(code Code, message string) Diagnostic {
	return Diagnostic{Code: code, Severity: SeverityError, Message: message}
}