package pgsql

import (
	"fmt"
	"io"
	"os"
	"sort"
	"strings"

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

// MigrationScript represents a single migration script with priority
type MigrationScript struct {
	ObjectName string
	ObjectType string
	Schema     string
	Priority   int
	Sequence   int
	Body       string
}

// MigrationWriter generates differential migration SQL scripts using templates
type MigrationWriter struct {
	options  *writers.WriterOptions
	writer   io.Writer
	executor *TemplateExecutor
}

// NewMigrationWriter creates a new templated migration writer
func NewMigrationWriter(options *writers.WriterOptions) (*MigrationWriter, error) {
	executor, err := NewTemplateExecutor()
	if err != nil {
		return nil, fmt.Errorf("failed to create template executor: %w", err)
	}

	return &MigrationWriter{
		options:  options,
		executor: executor,
	}, nil
}

// WriteMigration generates migration scripts using templates
func (w *MigrationWriter) WriteMigration(model *models.Database, current *models.Database) error {
	var writer io.Writer
	var file *os.File
	var err error

	// Use existing writer if already set (for testing)
	if w.writer != nil {
		writer = w.writer
	} else if w.options.OutputPath != "" {
		file, err = os.Create(w.options.OutputPath)
		if err != nil {
			return fmt.Errorf("failed to create output file: %w", err)
		}
		defer file.Close()
		writer = file
	} else {
		writer = os.Stdout
	}

	w.writer = writer

	// Check if audit is configured in metadata
	var auditConfig *AuditConfig
	if w.options.Metadata != nil {
		if ac, ok := w.options.Metadata["audit_config"].(*AuditConfig); ok {
			auditConfig = ac
		}
	}

	// Generate all migration scripts
	scripts := make([]MigrationScript, 0)

	// Generate audit tables if needed (priority 90)
	if auditConfig != nil && len(auditConfig.EnabledTables) > 0 {
		auditTableScript, err := w.generateAuditTablesScript(auditConfig)
		if err != nil {
			return fmt.Errorf("failed to generate audit tables: %w", err)
		}
		scripts = append(scripts, auditTableScript...)
	}

	// Process each schema in the model
	for _, modelSchema := range model.Schemas {
		// Find corresponding schema in current database
		var currentSchema *models.Schema
		for _, cs := range current.Schemas {
			if strings.EqualFold(cs.Name, modelSchema.Name) {
				currentSchema = cs
				break
			}
		}

		// Generate schema-level scripts
		schemaScripts, err := w.generateSchemaScripts(modelSchema, currentSchema)
		if err != nil {
			return fmt.Errorf("failed to generate schema scripts: %w", err)
		}
		scripts = append(scripts, schemaScripts...)

		// Generate audit scripts for this schema (if configured)
		if auditConfig != nil {
			auditScripts, err := w.generateAuditScripts(modelSchema, auditConfig)
			if err != nil {
				return fmt.Errorf("failed to generate audit scripts: %w", err)
			}
			scripts = append(scripts, auditScripts...)
		}
	}

	// Sort scripts by priority and sequence
	sort.Slice(scripts, func(i, j int) bool {
		if scripts[i].Priority != scripts[j].Priority {
			return scripts[i].Priority < scripts[j].Priority
		}
		return scripts[i].Sequence < scripts[j].Sequence
	})

	// Write header
	fmt.Fprintf(w.writer, "-- PostgreSQL Migration Script\n")
	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
	fmt.Fprintf(w.writer, "-- Source: %s -> %s\n\n", current.Name, model.Name)

	// Write scripts
	for _, script := range scripts {
		fmt.Fprintf(w.writer, "-- Priority: %d | Type: %s | Object: %s\n",
			script.Priority, script.ObjectType, script.ObjectName)
		fmt.Fprintf(w.writer, "%s\n\n", script.Body)
	}

	return nil
}

// generateSchemaScripts generates migration scripts for a schema using templates
func (w *MigrationWriter) generateSchemaScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Phase 1: Drop constraints and indexes that changed (Priority 11-50)
	if current != nil {
		dropScripts, err := w.generateDropScripts(model, current)
		if err != nil {
			return nil, fmt.Errorf("failed to generate drop scripts: %w", err)
		}
		scripts = append(scripts, dropScripts...)
	}

	// Phase 3: Create/Alter tables and columns (Priority 100-145)
	tableScripts, err := w.generateTableScripts(model, current)
	if err != nil {
		return nil, fmt.Errorf("failed to generate table scripts: %w", err)
	}
	scripts = append(scripts, tableScripts...)

	// Phase 4: Create indexes (Priority 160-180)
	indexScripts, err := w.generateIndexScripts(model, current)
	if err != nil {
		return nil, fmt.Errorf("failed to generate index scripts: %w", err)
	}
	scripts = append(scripts, indexScripts...)

	// Phase 5: Create foreign keys (Priority 195)
	fkScripts, err := w.generateForeignKeyScripts(model, current)
	if err != nil {
		return nil, fmt.Errorf("failed to generate foreign key scripts: %w", err)
	}
	scripts = append(scripts, fkScripts...)

	// Phase 6: Add comments (Priority 200+)
	commentScripts, err := w.generateCommentScripts(model, current)
	if err != nil {
		return nil, fmt.Errorf("failed to generate comment scripts: %w", err)
	}
	scripts = append(scripts, commentScripts...)

	return scripts, nil
}

// generateDropScripts generates DROP scripts using templates
func (w *MigrationWriter) generateDropScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Build map of model tables for quick lookup
	modelTables := make(map[string]*models.Table)
	for _, table := range model.Tables {
		modelTables[strings.ToLower(table.Name)] = table
	}

	// Find constraints to drop
	for _, currentTable := range current.Tables {
		modelTable, existsInModel := modelTables[strings.ToLower(currentTable.Name)]

		if !existsInModel {
			continue
		}

		// Check each constraint in current database
		for constraintName, currentConstraint := range currentTable.Constraints {
			modelConstraint, existsInModel := modelTable.Constraints[constraintName]

			shouldDrop := false
			if !existsInModel {
				shouldDrop = true
			} else if !constraintsEqual(modelConstraint, currentConstraint) {
				shouldDrop = true
			}

			if shouldDrop {
				sql, err := w.executor.ExecuteDropConstraint(DropConstraintData{
					SchemaName:     current.Name,
					TableName:      currentTable.Name,
					ConstraintName: constraintName,
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", current.Name, currentTable.Name, constraintName),
					ObjectType: "drop constraint",
					Schema:     current.Name,
					Priority:   11,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}
		}

		// Check indexes
		for indexName, currentIndex := range currentTable.Indexes {
			modelIndex, existsInModel := modelTable.Indexes[indexName]

			shouldDrop := false
			if !existsInModel {
				shouldDrop = true
			} else if !indexesEqual(modelIndex, currentIndex) {
				shouldDrop = true
			}

			if shouldDrop {
				sql, err := w.executor.ExecuteDropIndex(DropIndexData{
					SchemaName: current.Name,
					IndexName:  indexName,
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", current.Name, currentTable.Name, indexName),
					ObjectType: "drop index",
					Schema:     current.Name,
					Priority:   20,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}
		}
	}

	return scripts, nil
}

// generateTableScripts generates CREATE/ALTER TABLE scripts using templates
func (w *MigrationWriter) generateTableScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Build map of current tables
	currentTables := make(map[string]*models.Table)
	if current != nil {
		for _, table := range current.Tables {
			currentTables[strings.ToLower(table.Name)] = table
		}
	}

	// Process each model table
	for _, modelTable := range model.Tables {
		currentTable, exists := currentTables[strings.ToLower(modelTable.Name)]

		if !exists {
			// Table doesn't exist, create it
			sql, err := w.executor.ExecuteCreateTable(BuildCreateTableData(model.Name, modelTable))
			if err != nil {
				return nil, err
			}

			script := MigrationScript{
				ObjectName: fmt.Sprintf("%s.%s", model.Name, modelTable.Name),
				ObjectType: "create table",
				Schema:     model.Name,
				Priority:   100,
				Sequence:   len(scripts),
				Body:       sql,
			}
			scripts = append(scripts, script)
		} else {
			// Table exists, check for column changes
			alterScripts, err := w.generateAlterTableScripts(model, modelTable, currentTable)
			if err != nil {
				return nil, err
			}
			scripts = append(scripts, alterScripts...)
		}
	}

	return scripts, nil
}

// generateAlterTableScripts generates ALTER TABLE scripts using templates
func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, modelTable *models.Table, currentTable *models.Table) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Build map of current columns
	currentColumns := make(map[string]*models.Column)
	for name, col := range currentTable.Columns {
		currentColumns[strings.ToLower(name)] = col
	}

	// Check each model column
	for _, modelCol := range modelTable.Columns {
		currentCol, exists := currentColumns[strings.ToLower(modelCol.Name)]

		if !exists {
			// Column doesn't exist, add it
			defaultVal := ""
			if modelCol.Default != nil {
				defaultVal = fmt.Sprintf("%v", modelCol.Default)
			}

			sql, err := w.executor.ExecuteAddColumn(AddColumnData{
				SchemaName: schema.Name,
				TableName:  modelTable.Name,
				ColumnName: modelCol.Name,
				ColumnType: modelCol.Type,
				Default:    defaultVal,
				NotNull:    modelCol.NotNull,
			})
			if err != nil {
				return nil, err
			}

			script := MigrationScript{
				ObjectName: fmt.Sprintf("%s.%s.%s", schema.Name, modelTable.Name, modelCol.Name),
				ObjectType: "create column",
				Schema:     schema.Name,
				Priority:   120,
				Sequence:   len(scripts),
				Body:       sql,
			}
			scripts = append(scripts, script)
		} else if !columnsEqual(modelCol, currentCol) {
			// Column exists but properties changed
			if modelCol.Type != currentCol.Type {
				sql, err := w.executor.ExecuteAlterColumnType(AlterColumnTypeData{
					SchemaName: schema.Name,
					TableName:  modelTable.Name,
					ColumnName: modelCol.Name,
					NewType:    modelCol.Type,
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", schema.Name, modelTable.Name, modelCol.Name),
					ObjectType: "alter column type",
					Schema:     schema.Name,
					Priority:   120,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}

			// Check default value changes
			if fmt.Sprintf("%v", modelCol.Default) != fmt.Sprintf("%v", currentCol.Default) {
				setDefault := modelCol.Default != nil
				defaultVal := ""
				if setDefault {
					defaultVal = fmt.Sprintf("%v", modelCol.Default)
				}

				sql, err := w.executor.ExecuteAlterColumnDefault(AlterColumnDefaultData{
					SchemaName:   schema.Name,
					TableName:    modelTable.Name,
					ColumnName:   modelCol.Name,
					SetDefault:   setDefault,
					DefaultValue: defaultVal,
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", schema.Name, modelTable.Name, modelCol.Name),
					ObjectType: "alter column default",
					Schema:     schema.Name,
					Priority:   145,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}
		}
	}

	return scripts, nil
}

// generateIndexScripts generates CREATE INDEX scripts using templates
func (w *MigrationWriter) generateIndexScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Build map of current tables
	currentTables := make(map[string]*models.Table)
	if current != nil {
		for _, table := range current.Tables {
			currentTables[strings.ToLower(table.Name)] = table
		}
	}

	// Process each model table
	for _, modelTable := range model.Tables {
		currentTable := currentTables[strings.ToLower(modelTable.Name)]

		// Process primary keys first
		for constraintName, constraint := range modelTable.Constraints {
			if constraint.Type == models.PrimaryKeyConstraint {
				shouldCreate := true

				if currentTable != nil {
					if currentConstraint, exists := currentTable.Constraints[constraintName]; exists {
						if constraintsEqual(constraint, currentConstraint) {
							shouldCreate = false
						}
					}
				}

				if shouldCreate {
					sql, err := w.executor.ExecuteCreatePrimaryKey(CreatePrimaryKeyData{
						SchemaName:     model.Name,
						TableName:      modelTable.Name,
						ConstraintName: constraintName,
						Columns:        strings.Join(constraint.Columns, ", "),
					})
					if err != nil {
						return nil, err
					}

					script := MigrationScript{
						ObjectName: fmt.Sprintf("%s.%s.%s", model.Name, modelTable.Name, constraintName),
						ObjectType: "create primary key",
						Schema:     model.Name,
						Priority:   160,
						Sequence:   len(scripts),
						Body:       sql,
					}
					scripts = append(scripts, script)
				}
			}
		}

		// Process indexes
		for indexName, modelIndex := range modelTable.Indexes {
			// Skip primary key indexes
			if strings.HasPrefix(strings.ToLower(indexName), "pk_") {
				continue
			}

			shouldCreate := true

			if currentTable != nil {
				if currentIndex, exists := currentTable.Indexes[indexName]; exists {
					if indexesEqual(modelIndex, currentIndex) {
						shouldCreate = false
					}
				}
			}

			if shouldCreate {
				indexType := "btree"
				if modelIndex.Type != "" {
					indexType = modelIndex.Type
				}

				sql, err := w.executor.ExecuteCreateIndex(CreateIndexData{
					SchemaName: model.Name,
					TableName:  modelTable.Name,
					IndexName:  indexName,
					IndexType:  indexType,
					Columns:    strings.Join(modelIndex.Columns, ", "),
					Unique:     modelIndex.Unique,
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", model.Name, modelTable.Name, indexName),
					ObjectType: "create index",
					Schema:     model.Name,
					Priority:   180,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}
		}
	}

	return scripts, nil
}

// generateForeignKeyScripts generates ADD CONSTRAINT FOREIGN KEY scripts using templates
func (w *MigrationWriter) generateForeignKeyScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Build map of current tables
	currentTables := make(map[string]*models.Table)
	if current != nil {
		for _, table := range current.Tables {
			currentTables[strings.ToLower(table.Name)] = table
		}
	}

	// Process each model table
	for _, modelTable := range model.Tables {
		currentTable := currentTables[strings.ToLower(modelTable.Name)]

		// Process each constraint
		for constraintName, constraint := range modelTable.Constraints {
			if constraint.Type != models.ForeignKeyConstraint {
				continue
			}

			shouldCreate := true

			if currentTable != nil {
				if currentConstraint, exists := currentTable.Constraints[constraintName]; exists {
					if constraintsEqual(constraint, currentConstraint) {
						shouldCreate = false
					}
				}
			}

			if shouldCreate {
				onDelete := "NO ACTION"
				if constraint.OnDelete != "" {
					onDelete = strings.ToUpper(constraint.OnDelete)
				}

				onUpdate := "NO ACTION"
				if constraint.OnUpdate != "" {
					onUpdate = strings.ToUpper(constraint.OnUpdate)
				}

				sql, err := w.executor.ExecuteCreateForeignKey(CreateForeignKeyData{
					SchemaName:     model.Name,
					TableName:      modelTable.Name,
					ConstraintName: constraintName,
					SourceColumns:  strings.Join(constraint.Columns, ", "),
					TargetSchema:   constraint.ReferencedSchema,
					TargetTable:    constraint.ReferencedTable,
					TargetColumns:  strings.Join(constraint.ReferencedColumns, ", "),
					OnDelete:       onDelete,
					OnUpdate:       onUpdate,
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", model.Name, modelTable.Name, constraintName),
					ObjectType: "create foreign key",
					Schema:     model.Name,
					Priority:   195,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}
		}
	}

	return scripts, nil
}

// generateCommentScripts generates COMMENT ON scripts using templates
func (w *MigrationWriter) generateCommentScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)
	_ = current // TODO: Compare with current schema to only add new/changed comments

	// Process each model table
	for _, modelTable := range model.Tables {
		// Table comment
		if modelTable.Description != "" {
			sql, err := w.executor.ExecuteCommentTable(CommentTableData{
				SchemaName: model.Name,
				TableName:  modelTable.Name,
				Comment:    escapeQuote(modelTable.Description),
			})
			if err != nil {
				return nil, err
			}

			script := MigrationScript{
				ObjectName: fmt.Sprintf("%s.%s", model.Name, modelTable.Name),
				ObjectType: "comment on table",
				Schema:     model.Name,
				Priority:   200,
				Sequence:   len(scripts),
				Body:       sql,
			}
			scripts = append(scripts, script)
		}

		// Column comments
		for _, col := range modelTable.Columns {
			if col.Description != "" {
				sql, err := w.executor.ExecuteCommentColumn(CommentColumnData{
					SchemaName: model.Name,
					TableName:  modelTable.Name,
					ColumnName: col.Name,
					Comment:    escapeQuote(col.Description),
				})
				if err != nil {
					return nil, err
				}

				script := MigrationScript{
					ObjectName: fmt.Sprintf("%s.%s.%s", model.Name, modelTable.Name, col.Name),
					ObjectType: "comment on column",
					Schema:     model.Name,
					Priority:   200,
					Sequence:   len(scripts),
					Body:       sql,
				}
				scripts = append(scripts, script)
			}
		}
	}

	return scripts, nil
}

// generateAuditTablesScript generates audit table creation scripts using templates
func (w *MigrationWriter) generateAuditTablesScript(auditConfig *AuditConfig) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	auditSchema := auditConfig.AuditSchema
	if auditSchema == "" {
		auditSchema = "public"
	}

	sql, err := w.executor.ExecuteAuditTables(AuditTablesData{
		AuditSchema: auditSchema,
	})
	if err != nil {
		return nil, err
	}

	script := MigrationScript{
		ObjectName: fmt.Sprintf("%s.atevent+atdetail", auditSchema),
		ObjectType: "create audit tables",
		Schema:     auditSchema,
		Priority:   90,
		Sequence:   0,
		Body:       sql,
	}
	scripts = append(scripts, script)

	return scripts, nil
}

// generateAuditScripts generates audit functions and triggers using templates
func (w *MigrationWriter) generateAuditScripts(schema *models.Schema, auditConfig *AuditConfig) ([]MigrationScript, error) {
	scripts := make([]MigrationScript, 0)

	// Process each table in the schema
	for _, table := range schema.Tables {
		if !auditConfig.IsTableAudited(schema.Name, table.Name) {
			continue
		}

		config := auditConfig.GetTableConfig(schema.Name, table.Name)
		if config == nil {
			continue
		}

		// Find primary key
		pk := table.GetPrimaryKey()
		if pk == nil {
			continue
		}

		auditSchema := auditConfig.AuditSchema
		if auditSchema == "" {
			auditSchema = schema.Name
		}

		// Generate audit function
		funcName := fmt.Sprintf("ft_audit_%s", table.Name)
		funcData := BuildAuditFunctionData(schema.Name, table, pk, config, auditSchema, auditConfig.UserFunction)

		funcSQL, err := w.executor.ExecuteAuditFunction(funcData)
		if err != nil {
			return nil, err
		}

		functionScript := MigrationScript{
			ObjectName: fmt.Sprintf("%s.%s", schema.Name, funcName),
			ObjectType: "create audit function",
			Schema:     schema.Name,
			Priority:   345,
			Sequence:   len(scripts),
			Body:       funcSQL,
		}
		scripts = append(scripts, functionScript)

		// Generate audit trigger
		triggerName := fmt.Sprintf("t_audit_%s", table.Name)
		events := make([]string, 0)
		if config.AuditInsert {
			events = append(events, "INSERT")
		}
		if config.AuditUpdate {
			events = append(events, "UPDATE")
		}
		if config.AuditDelete {
			events = append(events, "DELETE")
		}

		if len(events) == 0 {
			continue
		}

		triggerSQL, err := w.executor.ExecuteAuditTrigger(AuditTriggerData{
			SchemaName:   schema.Name,
			TableName:    table.Name,
			TriggerName:  triggerName,
			FunctionName: funcName,
			Events:       strings.Join(events, " OR "),
		})
		if err != nil {
			return nil, err
		}

		triggerScript := MigrationScript{
			ObjectName: fmt.Sprintf("%s.%s", schema.Name, triggerName),
			ObjectType: "create audit trigger",
			Schema:     schema.Name,
			Priority:   355,
			Sequence:   len(scripts),
			Body:       triggerSQL,
		}
		scripts = append(scripts, triggerScript)
	}

	return scripts, nil
}

// Helper functions for comparing database objects

// columnsEqual checks if two columns have the same definition
func columnsEqual(col1, col2 *models.Column) bool {
	if col1 == nil || col2 == nil {
		return false
	}
	return strings.EqualFold(col1.Type, col2.Type) &&
		col1.NotNull == col2.NotNull &&
		fmt.Sprintf("%v", col1.Default) == fmt.Sprintf("%v", col2.Default)
}

// constraintsEqual checks if two constraints are equal
func constraintsEqual(c1, c2 *models.Constraint) bool {
	if c1 == nil || c2 == nil {
		return false
	}
	if c1.Type != c2.Type {
		return false
	}

	// Compare columns
	if len(c1.Columns) != len(c2.Columns) {
		return false
	}
	for i, col := range c1.Columns {
		if !strings.EqualFold(col, c2.Columns[i]) {
			return false
		}
	}

	// For foreign keys, also compare referenced table and columns
	if c1.Type == models.ForeignKeyConstraint {
		if !strings.EqualFold(c1.ReferencedTable, c2.ReferencedTable) {
			return false
		}
		if len(c1.ReferencedColumns) != len(c2.ReferencedColumns) {
			return false
		}
		for i, col := range c1.ReferencedColumns {
			if !strings.EqualFold(col, c2.ReferencedColumns[i]) {
				return false
			}
		}
		if c1.OnDelete != c2.OnDelete || c1.OnUpdate != c2.OnUpdate {
			return false
		}
	}

	return true
}

// indexesEqual checks if two indexes are equal
func indexesEqual(idx1, idx2 *models.Index) bool {
	if idx1 == nil || idx2 == nil {
		return false
	}
	if idx1.Unique != idx2.Unique {
		return false
	}
	if !strings.EqualFold(idx1.Type, idx2.Type) {
		return false
	}
	if len(idx1.Columns) != len(idx2.Columns) {
		return false
	}
	for i, col := range idx1.Columns {
		if !strings.EqualFold(col, idx2.Columns[i]) {
			return false
		}
	}
	return true
}