package mssql

import (
	"context"
	"database/sql"
	"fmt"

	_ "github.com/microsoft/go-mssqldb" // MSSQL driver

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

// Reader implements the readers.Reader interface for MSSQL databases
type Reader struct {
	options *readers.ReaderOptions
	db      *sql.DB
	ctx     context.Context
}

// NewReader creates a new MSSQL reader
func NewReader(options *readers.ReaderOptions) *Reader {
	return &Reader{
		options: options,
		ctx:     context.Background(),
	}
}

// ReadDatabase reads the entire database schema from MSSQL
func (r *Reader) ReadDatabase() (*models.Database, error) {
	// Validate connection string
	if r.options.ConnectionString == "" {
		return nil, fmt.Errorf("connection string is required")
	}

	// Connect to the database
	if err := r.connect(); err != nil {
		return nil, fmt.Errorf("failed to connect: %w", err)
	}
	defer r.close()

	// Get database name
	var dbName string
	err := r.db.QueryRowContext(r.ctx, "SELECT DB_NAME()").Scan(&dbName)
	if err != nil {
		return nil, fmt.Errorf("failed to get database name: %w", err)
	}

	// Initialize database model
	db := models.InitDatabase(dbName)
	db.DatabaseType = models.MSSQLDatabaseType
	db.SourceFormat = "mssql"

	// Get MSSQL version
	var version string
	err = r.db.QueryRowContext(r.ctx, "SELECT @@VERSION").Scan(&version)
	if err == nil {
		db.DatabaseVersion = version
	}

	// Query all schemas
	schemas, err := r.querySchemas()
	if err != nil {
		return nil, fmt.Errorf("failed to query schemas: %w", err)
	}

	// Process each schema
	for _, schema := range schemas {
		// Query tables for this schema
		tables, err := r.queryTables(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query tables for schema %s: %w", schema.Name, err)
		}
		schema.Tables = tables

		// Query columns for tables
		columnsMap, err := r.queryColumns(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query columns for schema %s: %w", schema.Name, err)
		}

		// Populate table columns
		for _, table := range schema.Tables {
			tableKey := schema.Name + "." + table.Name
			if cols, exists := columnsMap[tableKey]; exists {
				table.Columns = cols
			}
		}

		// Query primary keys
		primaryKeys, err := r.queryPrimaryKeys(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query primary keys for schema %s: %w", schema.Name, err)
		}

		// Apply primary keys to tables
		for _, table := range schema.Tables {
			tableKey := schema.Name + "." + table.Name
			if pk, exists := primaryKeys[tableKey]; exists {
				table.Constraints[pk.Name] = pk
				// Mark columns as primary key and not null
				for _, colName := range pk.Columns {
					if col, colExists := table.Columns[colName]; colExists {
						col.IsPrimaryKey = true
						col.NotNull = true
					}
				}
			}
		}

		// Query foreign keys
		foreignKeys, err := r.queryForeignKeys(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query foreign keys for schema %s: %w", schema.Name, err)
		}

		// Apply foreign keys to tables
		for _, table := range schema.Tables {
			tableKey := schema.Name + "." + table.Name
			if fks, exists := foreignKeys[tableKey]; exists {
				for _, fk := range fks {
					table.Constraints[fk.Name] = fk
					// Derive relationship from foreign key
					r.deriveRelationship(table, fk)
				}
			}
		}

		// Query unique constraints
		uniqueConstraints, err := r.queryUniqueConstraints(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query unique constraints for schema %s: %w", schema.Name, err)
		}

		// Apply unique constraints to tables
		for _, table := range schema.Tables {
			tableKey := schema.Name + "." + table.Name
			if ucs, exists := uniqueConstraints[tableKey]; exists {
				for _, uc := range ucs {
					table.Constraints[uc.Name] = uc
				}
			}
		}

		// Query check constraints
		checkConstraints, err := r.queryCheckConstraints(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query check constraints for schema %s: %w", schema.Name, err)
		}

		// Apply check constraints to tables
		for _, table := range schema.Tables {
			tableKey := schema.Name + "." + table.Name
			if ccs, exists := checkConstraints[tableKey]; exists {
				for _, cc := range ccs {
					table.Constraints[cc.Name] = cc
				}
			}
		}

		// Query indexes
		indexes, err := r.queryIndexes(schema.Name)
		if err != nil {
			return nil, fmt.Errorf("failed to query indexes for schema %s: %w", schema.Name, err)
		}

		// Apply indexes to tables
		for _, table := range schema.Tables {
			tableKey := schema.Name + "." + table.Name
			if idxs, exists := indexes[tableKey]; exists {
				for _, idx := range idxs {
					table.Indexes[idx.Name] = idx
				}
			}
		}

		// Set RefDatabase for schema
		schema.RefDatabase = db

		// Set RefSchema for tables
		for _, table := range schema.Tables {
			table.RefSchema = schema
		}

		// Add schema to database
		db.Schemas = append(db.Schemas, schema)
	}

	return db, nil
}

// ReadSchema reads a single schema (returns the first schema from the database)
func (r *Reader) ReadSchema() (*models.Schema, error) {
	db, err := r.ReadDatabase()
	if err != nil {
		return nil, err
	}
	if len(db.Schemas) == 0 {
		return nil, fmt.Errorf("no schemas found in database")
	}
	return db.Schemas[0], nil
}

// ReadTable reads a single table (returns the first table from the first schema)
func (r *Reader) ReadTable() (*models.Table, error) {
	schema, err := r.ReadSchema()
	if err != nil {
		return nil, err
	}
	if len(schema.Tables) == 0 {
		return nil, fmt.Errorf("no tables found in schema")
	}
	return schema.Tables[0], nil
}

// connect establishes a connection to the MSSQL database
func (r *Reader) connect() error {
	db, err := sql.Open("mssql", r.options.ConnectionString)
	if err != nil {
		return err
	}

	// Test connection
	if err = db.PingContext(r.ctx); err != nil {
		db.Close()
		return err
	}

	r.db = db
	return nil
}

// close closes the database connection
func (r *Reader) close() {
	if r.db != nil {
		r.db.Close()
	}
}

// mapDataType maps MSSQL data types to canonical types
func (r *Reader) mapDataType(mssqlType string) string {
	return mssql.ConvertMSSQLToCanonical(mssqlType)
}

// deriveRelationship creates a relationship from a foreign key constraint
func (r *Reader) deriveRelationship(table *models.Table, fk *models.Constraint) {
	relationshipName := fmt.Sprintf("%s_to_%s", table.Name, fk.ReferencedTable)

	relationship := models.InitRelationship(relationshipName, models.OneToMany)
	relationship.FromTable = table.Name
	relationship.FromSchema = table.Schema
	relationship.ToTable = fk.ReferencedTable
	relationship.ToSchema = fk.ReferencedSchema
	relationship.ForeignKey = fk.Name

	// Store constraint actions in properties
	if fk.OnDelete != "" {
		relationship.Properties["on_delete"] = fk.OnDelete
	}
	if fk.OnUpdate != "" {
		relationship.Properties["on_update"] = fk.OnUpdate
	}

	table.Relationships[relationshipName] = relationship
}