package diff

import (
	"fmt"
	"reflect"
	"sort"
	"strconv"
	"strings"

	"git.warky.dev/wdevs/relspecgo/pkg/models"
)

// sortedKeys returns a map's keys sorted alphabetically, so callers get a
// deterministic iteration order instead of Go's randomized map order.
func sortedKeys[T any](m map[string]T) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}

// CompareDatabases compares two database models and returns the differences
func CompareDatabases(source, target *models.Database) *DiffResult {
	result := &DiffResult{
		Source:  source.Name,
		Target:  target.Name,
		Schemas: compareSchemas(source.Schemas, target.Schemas),
	}
	return result
}

func compareSchemas(source, target []*models.Schema) *SchemaDiff {
	diff := &SchemaDiff{
		Missing:  make([]*models.Schema, 0),
		Extra:    make([]*models.Schema, 0),
		Modified: make([]*SchemaChange, 0),
	}

	sourceMap := make(map[string]*models.Schema)
	targetMap := make(map[string]*models.Schema)

	for _, s := range source {
		sourceMap[s.SQLName()] = s
	}
	for _, t := range target {
		targetMap[t.SQLName()] = t
	}

	// Find missing and modified schemas
	for _, name := range sortedKeys(sourceMap) {
		srcSchema := sourceMap[name]
		if tgtSchema, exists := targetMap[name]; !exists {
			diff.Missing = append(diff.Missing, srcSchema)
		} else {
			if change := compareSchemaDetails(srcSchema, tgtSchema); change != nil {
				diff.Modified = append(diff.Modified, change)
			}
		}
	}

	// Find extra schemas
	for _, name := range sortedKeys(targetMap) {
		tgtSchema := targetMap[name]
		if _, exists := sourceMap[name]; !exists {
			diff.Extra = append(diff.Extra, tgtSchema)
		}
	}

	return diff
}

func compareSchemaDetails(source, target *models.Schema) *SchemaChange {
	change := &SchemaChange{
		Name: source.Name,
	}

	hasChanges := false

	// Compare tables
	tableDiff := compareTables(source.Tables, target.Tables)
	if !isEmpty(tableDiff) {
		change.Tables = tableDiff
		hasChanges = true
	}

	// Compare views
	viewDiff := compareViews(source.Views, target.Views)
	if !isEmpty(viewDiff) {
		change.Views = viewDiff
		hasChanges = true
	}

	// Compare sequences
	sequenceDiff := compareSequences(source.Sequences, target.Sequences)
	if !isEmpty(sequenceDiff) {
		change.Sequences = sequenceDiff
		hasChanges = true
	}

	// Compare scripts
	scriptDiff := compareScripts(source.Scripts, target.Scripts)
	if !isEmpty(scriptDiff) {
		change.Scripts = scriptDiff
		hasChanges = true
	}

	if !hasChanges {
		return nil
	}
	return change
}

func compareTables(source, target []*models.Table) *TableDiff {
	diff := &TableDiff{
		Missing:  make([]*models.Table, 0),
		Extra:    make([]*models.Table, 0),
		Modified: make([]*TableChange, 0),
	}

	sourceMap := make(map[string]*models.Table)
	targetMap := make(map[string]*models.Table)

	for _, t := range source {
		sourceMap[t.SQLName()] = t
	}
	for _, t := range target {
		targetMap[t.SQLName()] = t
	}

	// Find missing and modified tables
	for _, name := range sortedKeys(sourceMap) {
		srcTable := sourceMap[name]
		if tgtTable, exists := targetMap[name]; !exists {
			diff.Missing = append(diff.Missing, srcTable)
		} else {
			if change := compareTableDetails(srcTable, tgtTable); change != nil {
				diff.Modified = append(diff.Modified, change)
			}
		}
	}

	// Find extra tables
	for _, name := range sortedKeys(targetMap) {
		tgtTable := targetMap[name]
		if _, exists := sourceMap[name]; !exists {
			diff.Extra = append(diff.Extra, tgtTable)
		}
	}

	return diff
}

func compareTableDetails(source, target *models.Table) *TableChange {
	change := &TableChange{
		Name:   source.Name,
		Schema: source.Schema,
	}

	hasChanges := false

	// Compare columns
	columnDiff := compareColumns(source.Columns, target.Columns)
	if !isEmpty(columnDiff) {
		change.Columns = columnDiff
		hasChanges = true
	}

	// Compare indexes
	indexDiff := compareIndexes(source.Indexes, target.Indexes)
	if !isEmpty(indexDiff) {
		change.Indexes = indexDiff
		hasChanges = true
	}

	// Compare constraints
	constraintDiff := compareConstraints(source.Constraints, target.Constraints)
	if !isEmpty(constraintDiff) {
		change.Constraints = constraintDiff
		hasChanges = true
	}

	// Compare relationships
	relationshipDiff := compareRelationships(source.Relationships, target.Relationships)
	if !isEmpty(relationshipDiff) {
		change.Relationships = relationshipDiff
		hasChanges = true
	}

	if !hasChanges {
		return nil
	}
	return change
}

func compareColumns(source, target map[string]*models.Column) *ColumnDiff {
	diff := &ColumnDiff{
		Missing:  make([]*models.Column, 0),
		Extra:    make([]*models.Column, 0),
		Modified: make([]*ColumnChange, 0),
	}

	// Find missing and modified columns
	for _, name := range sortedKeys(source) {
		srcCol := source[name]
		if tgtCol, exists := target[name]; !exists {
			diff.Missing = append(diff.Missing, srcCol)
		} else {
			if changes := compareColumnDetails(srcCol, tgtCol); len(changes) > 0 {
				diff.Modified = append(diff.Modified, &ColumnChange{
					Name:    name,
					Source:  srcCol,
					Target:  tgtCol,
					Changes: changes,
				})
			}
		}
	}

	// Find extra columns
	for _, name := range sortedKeys(target) {
		tgtCol := target[name]
		if _, exists := source[name]; !exists {
			diff.Extra = append(diff.Extra, tgtCol)
		}
	}

	return diff
}

func compareColumnDetails(source, target *models.Column) map[string]any {
	changes := make(map[string]any)
	sourceType, sourceLength, sourceDefault := comparableColumn(source)
	targetType, targetLength, targetDefault := comparableColumn(target)

	if sourceType != targetType {
		changes["type"] = map[string]string{"source": source.Type, "target": target.Type}
	}
	if sourceLength != targetLength {
		changes["length"] = map[string]int{"source": source.Length, "target": target.Length}
	}
	if source.Precision != target.Precision {
		changes["precision"] = map[string]int{"source": source.Precision, "target": target.Precision}
	}
	if source.Scale != target.Scale {
		changes["scale"] = map[string]int{"source": source.Scale, "target": target.Scale}
	}
	if source.NotNull != target.NotNull {
		changes["not_null"] = map[string]bool{"source": source.NotNull, "target": target.NotNull}
	}
	if !reflect.DeepEqual(sourceDefault, targetDefault) {
		changes["default"] = map[string]any{"source": sourceDefault, "target": targetDefault}
	}
	if source.AutoIncrement != target.AutoIncrement {
		changes["auto_increment"] = map[string]bool{"source": source.AutoIncrement, "target": target.AutoIncrement}
	}
	if source.IsPrimaryKey != target.IsPrimaryKey {
		changes["is_primary_key"] = map[string]bool{"source": source.IsPrimaryKey, "target": target.IsPrimaryKey}
	}

	return changes
}

// comparableColumn accepts DBML's compact type/default spelling as well as
// PostgreSQL's normalized fields (for example varchar(255) vs varchar + 255).
func comparableColumn(column *models.Column) (string, int, any) {
	typeName := strings.TrimSpace(column.Type)
	defaultValue := column.Default
	lower := strings.ToLower(typeName)
	if i := strings.Index(lower, " default "); i >= 0 {
		if defaultValue == nil {
			defaultValue = strings.TrimSpace(typeName[i+len(" default "):])
		}
		typeName = strings.TrimSpace(typeName[:i])
	}
	length := column.Length
	if open := strings.LastIndex(typeName, "("); open >= 0 && strings.HasSuffix(typeName, ")") {
		if parsed, err := strconv.Atoi(strings.TrimSpace(typeName[open+1 : len(typeName)-1])); err == nil && length == 0 {
			length = parsed
		}
		typeName = strings.TrimSpace(typeName[:open])
	}
	return strings.ToLower(typeName), length, defaultValue
}

func compareIndexes(source, target map[string]*models.Index) *IndexDiff {
	diff := &IndexDiff{
		Missing:  make([]*models.Index, 0),
		Extra:    make([]*models.Index, 0),
		Modified: make([]*IndexChange, 0),
	}

	// Match by name first, then by definition. PostgreSQL and DBML can assign
	// different names to the same index (for example, posts_user_id_title_idx
	// and uidx_posts_user_id_title), so a name-only comparison reports false
	// drift after a merge/diff round trip.
	unmatchedSource := make(map[string]*models.Index, len(source))
	unmatchedTarget := make(map[string]*models.Index, len(target))
	for name, index := range source {
		unmatchedSource[name] = index
	}
	for name, index := range target {
		unmatchedTarget[name] = index
	}

	for _, name := range sortedKeys(source) {
		srcIdx := source[name]
		tgtIdx, exists := target[name]
		if !exists {
			continue
		}
		delete(unmatchedSource, name)
		delete(unmatchedTarget, name)
		if changes := compareIndexDetails(srcIdx, tgtIdx); len(changes) > 0 {
			diff.Modified = append(diff.Modified, &IndexChange{
				Name:    name,
				Source:  srcIdx,
				Target:  tgtIdx,
				Changes: changes,
			})
		}
	}

	// Pair remaining indexes by their structural identity, independent of the
	// generated/name field. The sorted iteration makes ambiguous matches
	// deterministic; duplicate definitions are still represented as separate
	// indexes by consuming one target at a time.
	remainingTarget := make(map[string][]*models.Index)
	for _, name := range sortedKeys(unmatchedTarget) {
		index := unmatchedTarget[name]
		key := indexDefinitionKey(index)
		remainingTarget[key] = append(remainingTarget[key], index)
	}
	for _, name := range sortedKeys(unmatchedSource) {
		srcIdx := unmatchedSource[name]
		key := indexDefinitionKey(srcIdx)
		candidates := remainingTarget[key]
		if len(candidates) == 0 {
			diff.Missing = append(diff.Missing, srcIdx)
			continue
		}
		tgtIdx := candidates[0]
		remainingTarget[key] = candidates[1:]
		if changes := compareIndexDetails(srcIdx, tgtIdx); len(changes) > 0 {
			diff.Modified = append(diff.Modified, &IndexChange{
				Name:    srcIdx.Name,
				Source:  srcIdx,
				Target:  tgtIdx,
				Changes: changes,
			})
		}
	}

	for _, key := range sortedKeys(remainingTarget) {
		for _, index := range remainingTarget[key] {
			diff.Extra = append(diff.Extra, index)
		}
	}
	return diff
}

func indexDefinitionKey(index *models.Index) string {
	return fmt.Sprintf("%t:%s:%s", index.Unique, strings.Join(index.Columns, ","), strings.Join(index.Include, ","))
}

func comparableIndexType(indexType string) string {
	indexType = strings.ToLower(strings.TrimSpace(indexType))
	if indexType == "" {
		return "btree"
	}
	return indexType
}

func compareIndexDetails(source, target *models.Index) map[string]any {
	changes := make(map[string]any)

	if !reflect.DeepEqual(source.Columns, target.Columns) {
		changes["columns"] = map[string][]string{"source": source.Columns, "target": target.Columns}
	}
	if source.Unique != target.Unique {
		changes["unique"] = map[string]bool{"source": source.Unique, "target": target.Unique}
	}
	if comparableIndexType(source.Type) != comparableIndexType(target.Type) {
		changes["type"] = map[string]string{"source": source.Type, "target": target.Type}
	}
	if source.Where != target.Where {
		changes["where"] = map[string]string{"source": source.Where, "target": target.Where}
	}

	return changes
}

// Compare constraints.
// Primary-key constraints are excluded: a PK is already represented by the
// column's IsPrimaryKey flag, which compareColumns already compares. The
// PostgreSQL reader additionally materialises each PK as a primary_key
// constraint and a unique btree index; the DBML reader keeps PKs as column
// flags only. Comparing the constraint maps directly would therefore report
// every PK as an "extra" constraint and the generated index as an "extra"
// index on a freshly-applied schema. Filtering them here keeps the round
// trip stable without losing real PK information.
func compareConstraints(source, target map[string]*models.Constraint) *ConstraintDiff {
	filteredSource := filterPrimaryKeyConstraints(source)
	filteredTarget := filterPrimaryKeyConstraints(target)
	sourceByKey := make(map[string]*models.Constraint, len(filteredSource))
	targetByKey := make(map[string]*models.Constraint, len(filteredTarget))
	for _, constraint := range filteredSource {
		sourceByKey[constraintCompareKey(constraint)] = constraint
	}
	for _, constraint := range filteredTarget {
		targetByKey[constraintCompareKey(constraint)] = constraint
	}
	diff := &ConstraintDiff{
		Missing:  make([]*models.Constraint, 0),
		Extra:    make([]*models.Constraint, 0),
		Modified: make([]*ConstraintChange, 0),
	}

	// Find missing and modified constraints
	for _, name := range sortedKeys(sourceByKey) {
		srcCon := sourceByKey[name]
		if tgtCon, exists := targetByKey[name]; !exists {
			diff.Missing = append(diff.Missing, srcCon)
		} else {
			if changes := compareConstraintDetails(srcCon, tgtCon); len(changes) > 0 {
				diff.Modified = append(diff.Modified, &ConstraintChange{
					Name:    name,
					Source:  srcCon,
					Target:  tgtCon,
					Changes: changes,
				})
			}
		}
	}

	// Find extra constraints
	for _, name := range sortedKeys(targetByKey) {
		tgtCon := targetByKey[name]
		if _, exists := sourceByKey[name]; !exists {
			diff.Extra = append(diff.Extra, tgtCon)
		}
	}

	return diff
}

// filterPrimaryKeyConstraints drops primary_key constraints from a single
// map. Primary keys are compared by the column IsPrimaryKey flag in
// compareColumns, so comparing the primary_key constraints here only
// produces duplicate "extra" entries (every PK is extra on the DBML side).
// Other constraint types are preserved untouched.
func filterPrimaryKeyConstraints(m map[string]*models.Constraint) map[string]*models.Constraint {
	out := make(map[string]*models.Constraint, len(m))
	for name, c := range m {
		if c.Type == models.PrimaryKeyConstraint {
			continue
		}
		out[name] = c
	}
	return out
}

func constraintCompareKey(constraint *models.Constraint) string {
	if constraint.Type != models.ForeignKeyConstraint {
		return constraint.SQLName()
	}
	return fmt.Sprintf("fk:%s:%s:%s:%s:%s:%s", strings.ToLower(constraint.Schema), strings.ToLower(constraint.Table), strings.Join(constraint.Columns, ","), strings.ToLower(constraint.ReferencedSchema), strings.ToLower(constraint.ReferencedTable), strings.Join(constraint.ReferencedColumns, ","))
}

func compareConstraintDetails(source, target *models.Constraint) map[string]any {
	changes := make(map[string]any)

	if source.Type != target.Type {
		changes["type"] = map[string]string{"source": string(source.Type), "target": string(target.Type)}
	}
	if !reflect.DeepEqual(source.Columns, target.Columns) {
		changes["columns"] = map[string][]string{"source": source.Columns, "target": target.Columns}
	}
	if source.ReferencedTable != target.ReferencedTable {
		changes["referenced_table"] = map[string]string{"source": source.ReferencedTable, "target": target.ReferencedTable}
	}
	if !reflect.DeepEqual(source.ReferencedColumns, target.ReferencedColumns) {
		changes["referenced_columns"] = map[string][]string{"source": source.ReferencedColumns, "target": target.ReferencedColumns}
	}
	if normalizeConstraintAction(source.OnDelete) != normalizeConstraintAction(target.OnDelete) {
		changes["on_delete"] = map[string]string{"source": source.OnDelete, "target": target.OnDelete}
	}
	if normalizeConstraintAction(source.OnUpdate) != normalizeConstraintAction(target.OnUpdate) {
		changes["on_update"] = map[string]string{"source": source.OnUpdate, "target": target.OnUpdate}
	}

	return changes
}

func normalizeConstraintAction(action string) string {
	if strings.EqualFold(strings.TrimSpace(action), "NO ACTION") {
		return ""
	}
	return strings.ToUpper(strings.TrimSpace(action))
}

func compareRelationships(source, target map[string]*models.Relationship) *RelationshipDiff {
	diff := &RelationshipDiff{
		Missing:  make([]*models.Relationship, 0),
		Extra:    make([]*models.Relationship, 0),
		Modified: make([]*RelationshipChange, 0),
	}

	// Find missing and modified relationships
	for _, name := range sortedKeys(source) {
		srcRel := source[name]
		if tgtRel, exists := target[name]; !exists {
			diff.Missing = append(diff.Missing, srcRel)
		} else {
			if changes := compareRelationshipDetails(srcRel, tgtRel); len(changes) > 0 {
				diff.Modified = append(diff.Modified, &RelationshipChange{
					Name:    name,
					Source:  srcRel,
					Target:  tgtRel,
					Changes: changes,
				})
			}
		}
	}

	// Find extra relationships
	for _, name := range sortedKeys(target) {
		tgtRel := target[name]
		if _, exists := source[name]; !exists {
			diff.Extra = append(diff.Extra, tgtRel)
		}
	}

	return diff
}

func compareRelationshipDetails(source, target *models.Relationship) map[string]any {
	changes := make(map[string]any)

	if source.Type != target.Type {
		changes["type"] = map[string]string{"source": string(source.Type), "target": string(target.Type)}
	}
	if source.FromTable != target.FromTable {
		changes["from_table"] = map[string]string{"source": source.FromTable, "target": target.FromTable}
	}
	if source.ToTable != target.ToTable {
		changes["to_table"] = map[string]string{"source": source.ToTable, "target": target.ToTable}
	}
	if !reflect.DeepEqual(source.FromColumns, target.FromColumns) {
		changes["from_columns"] = map[string][]string{"source": source.FromColumns, "target": target.FromColumns}
	}
	if !reflect.DeepEqual(source.ToColumns, target.ToColumns) {
		changes["to_columns"] = map[string][]string{"source": source.ToColumns, "target": target.ToColumns}
	}

	return changes
}

func compareViews(source, target []*models.View) *ViewDiff {
	diff := &ViewDiff{
		Missing:  make([]*models.View, 0),
		Extra:    make([]*models.View, 0),
		Modified: make([]*ViewChange, 0),
	}

	sourceMap := make(map[string]*models.View)
	targetMap := make(map[string]*models.View)

	for _, v := range source {
		sourceMap[v.SQLName()] = v
	}
	for _, v := range target {
		targetMap[v.SQLName()] = v
	}

	// Find missing and modified views
	for _, name := range sortedKeys(sourceMap) {
		srcView := sourceMap[name]
		if tgtView, exists := targetMap[name]; !exists {
			diff.Missing = append(diff.Missing, srcView)
		} else {
			if changes := compareViewDetails(srcView, tgtView); len(changes) > 0 {
				diff.Modified = append(diff.Modified, &ViewChange{
					Name:    name,
					Source:  srcView,
					Target:  tgtView,
					Changes: changes,
				})
			}
		}
	}

	// Find extra views
	for _, name := range sortedKeys(targetMap) {
		tgtView := targetMap[name]
		if _, exists := sourceMap[name]; !exists {
			diff.Extra = append(diff.Extra, tgtView)
		}
	}

	return diff
}

func compareViewDetails(source, target *models.View) map[string]any {
	changes := make(map[string]any)

	if source.Definition != target.Definition {
		changes["definition"] = map[string]string{"source": source.Definition, "target": target.Definition}
	}

	return changes
}

func compareSequences(source, target []*models.Sequence) *SequenceDiff {
	diff := &SequenceDiff{
		Missing:  make([]*models.Sequence, 0),
		Extra:    make([]*models.Sequence, 0),
		Modified: make([]*SequenceChange, 0),
	}

	sourceMap := make(map[string]*models.Sequence)
	targetMap := make(map[string]*models.Sequence)

	for _, s := range source {
		sourceMap[s.SQLName()] = s
	}
	for _, s := range target {
		targetMap[s.SQLName()] = s
	}

	// Find missing and modified sequences
	for _, name := range sortedKeys(sourceMap) {
		srcSeq := sourceMap[name]
		if tgtSeq, exists := targetMap[name]; !exists {
			diff.Missing = append(diff.Missing, srcSeq)
		} else {
			if changes := compareSequenceDetails(srcSeq, tgtSeq); len(changes) > 0 {
				diff.Modified = append(diff.Modified, &SequenceChange{
					Name:    name,
					Source:  srcSeq,
					Target:  tgtSeq,
					Changes: changes,
				})
			}
		}
	}

	// Find extra sequences
	for _, name := range sortedKeys(targetMap) {
		tgtSeq := targetMap[name]
		if _, exists := sourceMap[name]; !exists {
			diff.Extra = append(diff.Extra, tgtSeq)
		}
	}

	return diff
}

func compareSequenceDetails(source, target *models.Sequence) map[string]any {
	changes := make(map[string]any)

	if source.StartValue != target.StartValue {
		changes["start_value"] = map[string]int64{"source": source.StartValue, "target": target.StartValue}
	}
	if source.IncrementBy != target.IncrementBy {
		changes["increment_by"] = map[string]int64{"source": source.IncrementBy, "target": target.IncrementBy}
	}
	if source.MinValue != target.MinValue {
		changes["min_value"] = map[string]int64{"source": source.MinValue, "target": target.MinValue}
	}
	if source.MaxValue != target.MaxValue {
		changes["max_value"] = map[string]int64{"source": source.MaxValue, "target": target.MaxValue}
	}
	if source.Cycle != target.Cycle {
		changes["cycle"] = map[string]bool{"source": source.Cycle, "target": target.Cycle}
	}

	return changes
}

func compareScripts(source, target []*models.Script) *ScriptDiff {
	diff := &ScriptDiff{
		Missing:  make([]*models.Script, 0),
		Extra:    make([]*models.Script, 0),
		Modified: make([]*ScriptChange, 0),
	}

	sourceMap := make(map[string]*models.Script)
	targetMap := make(map[string]*models.Script)

	for _, s := range source {
		sourceMap[scriptCompareKey(s)] = s
	}
	for _, s := range target {
		targetMap[scriptCompareKey(s)] = s
	}

	for _, name := range sortedKeys(sourceMap) {
		srcScript := sourceMap[name]
		if tgtScript, exists := targetMap[name]; !exists {
			diff.Missing = append(diff.Missing, srcScript)
		} else if changes := compareScriptDetails(srcScript, tgtScript); len(changes) > 0 {
			diff.Modified = append(diff.Modified, &ScriptChange{
				Name:    srcScript.Name,
				Source:  srcScript,
				Target:  tgtScript,
				Changes: changes,
			})
		}
	}

	for _, name := range sortedKeys(targetMap) {
		tgtScript := targetMap[name]
		if _, exists := sourceMap[name]; !exists {
			diff.Extra = append(diff.Extra, tgtScript)
		}
	}

	return diff
}

func scriptCompareKey(script *models.Script) string {
	return fmt.Sprintf("%d:%d:%s", script.Priority, script.Sequence, script.SQLName())
}

func compareScriptDetails(source, target *models.Script) map[string]any {
	changes := make(map[string]any)

	if source.SQL != target.SQL {
		changes["sql"] = map[string]string{"source": source.SQL, "target": target.SQL}
	}
	if source.Rollback != target.Rollback {
		changes["rollback"] = map[string]string{"source": source.Rollback, "target": target.Rollback}
	}
	if !reflect.DeepEqual(source.RunAfter, target.RunAfter) {
		changes["run_after"] = map[string][]string{"source": source.RunAfter, "target": target.RunAfter}
	}
	if source.Schema != target.Schema {
		changes["schema"] = map[string]string{"source": source.Schema, "target": target.Schema}
	}
	if source.Version != target.Version {
		changes["version"] = map[string]string{"source": source.Version, "target": target.Version}
	}
	if source.Priority != target.Priority {
		changes["priority"] = map[string]int{"source": source.Priority, "target": target.Priority}
	}
	if source.Sequence != target.Sequence {
		changes["sequence"] = map[string]uint{"source": source.Sequence, "target": target.Sequence}
	}

	return changes
}

// Helper function to check if a diff is empty
func isEmpty(v any) bool {
	switch d := v.(type) {
	case *TableDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *ColumnDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *IndexDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *ConstraintDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *RelationshipDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *ViewDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *SequenceDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	case *ScriptDiff:
		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
	default:
		return false
	}
}

// ComputeSummary generates a summary with counts from a DiffResult
func ComputeSummary(result *DiffResult) *Summary {
	summary := &Summary{}

	if result.Schemas != nil {
		summary.Schemas = SchemaSummary{
			Missing:  len(result.Schemas.Missing),
			Extra:    len(result.Schemas.Extra),
			Modified: len(result.Schemas.Modified),
		}

		// Aggregate table/column/index/constraint counts
		for _, schemaChange := range result.Schemas.Modified {
			if schemaChange.Tables != nil {
				summary.Tables.Missing += len(schemaChange.Tables.Missing)
				summary.Tables.Extra += len(schemaChange.Tables.Extra)
				summary.Tables.Modified += len(schemaChange.Tables.Modified)

				for _, tableChange := range schemaChange.Tables.Modified {
					if tableChange.Columns != nil {
						summary.Columns.Missing += len(tableChange.Columns.Missing)
						summary.Columns.Extra += len(tableChange.Columns.Extra)
						summary.Columns.Modified += len(tableChange.Columns.Modified)
					}
					if tableChange.Indexes != nil {
						summary.Indexes.Missing += len(tableChange.Indexes.Missing)
						summary.Indexes.Extra += len(tableChange.Indexes.Extra)
						summary.Indexes.Modified += len(tableChange.Indexes.Modified)
					}
					if tableChange.Constraints != nil {
						summary.Constraints.Missing += len(tableChange.Constraints.Missing)
						summary.Constraints.Extra += len(tableChange.Constraints.Extra)
						summary.Constraints.Modified += len(tableChange.Constraints.Modified)
					}
					if tableChange.Relationships != nil {
						summary.Relationships.Missing += len(tableChange.Relationships.Missing)
						summary.Relationships.Extra += len(tableChange.Relationships.Extra)
						summary.Relationships.Modified += len(tableChange.Relationships.Modified)
					}
				}
			}
			if schemaChange.Views != nil {
				summary.Views.Missing += len(schemaChange.Views.Missing)
				summary.Views.Extra += len(schemaChange.Views.Extra)
				summary.Views.Modified += len(schemaChange.Views.Modified)
			}
			if schemaChange.Sequences != nil {
				summary.Sequences.Missing += len(schemaChange.Sequences.Missing)
				summary.Sequences.Extra += len(schemaChange.Sequences.Extra)
				summary.Sequences.Modified += len(schemaChange.Sequences.Modified)
			}
			if schemaChange.Scripts != nil {
				summary.Scripts.Missing += len(schemaChange.Scripts.Missing)
				summary.Scripts.Extra += len(schemaChange.Scripts.Extra)
				summary.Scripts.Modified += len(schemaChange.Scripts.Modified)
			}
		}
	}

	return summary
}