package engine

import "gitea.maximumdirect.net/eric/ConfigKit/internal/document"

type sequenceMode uint8

const (
	sequenceModeReplace sequenceMode = iota + 1
	sequenceModeAppend
	sequenceModeUpsert
)

type sequenceDeclarationSpec struct {
	path                Path
	location            Location
	destination         Path
	destinationLocation Location
	identityFields      []string
	identityPresent     bool
	identityLocation    *Location
	mode                sequenceMode
	modePresent         bool
	modeLocation        *Location
}

func parseSequenceDeclarationDirective(node *document.Node, directivePath Path) ([]sequenceDeclarationSpec, []Diagnostic) {
	if node == nil || node.Kind != document.Sequence {
		return nil, []Diagnostic{sequenceDeclarationDiagnostic(directivePath, "sequences must be a sequence", node)}
	}
	declarations := make([]sequenceDeclarationSpec, 0, len(node.Sequence))
	var diagnostics []Diagnostic
	for index, declarationNode := range node.Sequence {
		declaration, issues := parseSequenceDeclarationSpec(declarationNode, directivePath.Index(index))
		if len(issues) != 0 {
			diagnostics = append(diagnostics, issues...)
			continue
		}
		declarations = append(declarations, declaration)
	}
	return declarations, canonicalDiagnostics(diagnostics)
}

func parseSequenceDeclarationSpec(node *document.Node, declarationPath Path) (sequenceDeclarationSpec, []Diagnostic) {
	if node == nil || node.Kind != document.Mapping {
		return sequenceDeclarationSpec{}, []Diagnostic{sequenceDeclarationDiagnostic(declarationPath, "sequence declaration must be a mapping", node)}
	}
	declaration := sequenceDeclarationSpec{
		path:     declarationPath.clone(),
		location: publicLocation(node.Location),
	}
	destinationPresent := false
	for _, entry := range node.Mapping {
		fieldPath := declarationPath.Key(entry.Key)
		switch entry.Key {
		case "destination":
			destinationPresent = true
			destination, diagnostic := parseImportDestination(entry.Value, fieldPath)
			if diagnostic != nil {
				diagnostic.Code = CodeSequenceInvalid
				return sequenceDeclarationSpec{}, []Diagnostic{*diagnostic}
			}
			declaration.destination = destination
			declaration.destinationLocation = publicLocation(entry.Value.Location)
		case "key":
			fields, locations, errIndex, valid := parseSequenceIdentityFieldSet(entry.Value)
			if !valid {
				badPath := fieldPath
				badNode := entry.Value
				message := "key must be a string or nonempty list of strings"
				if errIndex >= 0 && entry.Value != nil {
					badPath = fieldPath.Index(errIndex)
					if errIndex < len(entry.Value.Sequence) {
						badNode = entry.Value.Sequence[errIndex]
					}
				}
				return sequenceDeclarationSpec{}, []Diagnostic{sequenceDeclarationDiagnostic(badPath, message, badNode)}
			}
			declaration.identityFields = fields
			declaration.identityPresent = true
			location := publicLocation(entry.Value.Location)
			if len(locations) != 0 {
				location = publicLocation(locations[0])
			}
			declaration.identityLocation = &location
		case "mode":
			if entry.Value == nil || entry.Value.Kind != document.String {
				return sequenceDeclarationSpec{}, []Diagnostic{sequenceDeclarationDiagnostic(fieldPath, "mode must be replace, append, or upsert", entry.Value)}
			}
			mode, ok := parseSequenceMode(entry.Value.Text)
			if !ok {
				return sequenceDeclarationSpec{}, []Diagnostic{sequenceDeclarationDiagnostic(fieldPath, "mode must be replace, append, or upsert", entry.Value)}
			}
			declaration.mode = mode
			declaration.modePresent = true
			location := publicLocation(entry.Value.Location)
			declaration.modeLocation = &location
		default:
			return sequenceDeclarationSpec{}, []Diagnostic{sequenceDeclarationDiagnostic(fieldPath, "sequence declaration field is not recognized", entry.Value)}
		}
	}
	if !destinationPresent {
		return sequenceDeclarationSpec{}, []Diagnostic{sequenceDeclarationDiagnostic(declarationPath.Key("destination"), "sequence declaration requires a destination", node)}
	}
	return declaration, nil
}

func parseSequenceIdentityFieldSet(node *document.Node) ([]string, []document.Location, int, bool) {
	if node == nil {
		return nil, nil, -1, false
	}
	var fields []string
	var locations []document.Location
	switch node.Kind {
	case document.String:
		fields = []string{node.Text}
		locations = []document.Location{node.Location}
	case document.Sequence:
		if len(node.Sequence) == 0 {
			return nil, nil, -1, false
		}
		for index, member := range node.Sequence {
			if member == nil || member.Kind != document.String {
				return nil, nil, index, false
			}
			fields = append(fields, member.Text)
			locations = append(locations, member.Location)
		}
	default:
		return nil, nil, -1, false
	}
	normalized, err := normalizeSequenceIdentityFields(fields)
	if err != nil {
		return nil, nil, -1, false
	}
	return normalized, locations, -1, true
}

func parseSequenceMode(value string) (sequenceMode, bool) {
	switch value {
	case "replace":
		return sequenceModeReplace, true
	case "append":
		return sequenceModeAppend, true
	case "upsert":
		return sequenceModeUpsert, true
	default:
		return 0, false
	}
}

func sequenceDeclarationDiagnostic(path Path, message string, node *document.Node) Diagnostic {
	var primary *Location
	if node != nil {
		location := publicLocation(node.Location)
		primary = &location
	}
	return Diagnostic{Code: CodeSequenceInvalid, Severity: SeverityError, Path: path, Message: message, Primary: primary}
}