package main

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

	"sync"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
	_ "github.com/microsoft/go-mssqldb"
	log "github.com/sirupsen/logrus"
)

type MigrationJob struct {
	Schema string
	Table  string
}

var migrationJobs []MigrationJob = []MigrationJob{
	{
		Schema: "Cartografia",
		Table:  "MANZANA",
	},
}

func main() {
	configureLog()
	log.Info("Starting migration...")
	log.Debugf("Migration jobs: %+v", migrationJobs)

	sourceDb, targetDb, connError := connectToDatabases()
	if connError != nil {
		log.Fatal("Connection error: ", connError)
	}

	defer sourceDb.Close()
	defer targetDb.Close()

	for _, job := range migrationJobs {
		sourceColTypes, targetColTypes, err := queryColumnTypes(sourceDb, targetDb, job)
		if err != nil {
			log.Fatal("Unexpected error: ", err)
		}

		log.Debugf("Source col types: %+v", sourceColTypes)
		log.Debugf("Target col types: %+v", targetColTypes)
	}

	log.Info("Migration completed successfully!")
}

func querySourceColTypes(db *sql.DB, migrationJob MigrationJob) ([]ColumnType, error) {
	query := `
SELECT 
	c.name AS name,
	t.name AS user_type,
	CASE WHEN t.is_user_defined = 0 THEN t.name ELSE bt.name END AS system_type,
	c.is_nullable AS nullable,
	c.max_length AS max_length,
	c.precision AS precision,
	c.scale AS scale
FROM sys.columns c
JOIN sys.types t ON c.user_type_id = t.user_type_id
LEFT JOIN sys.types bt ON t.is_user_defined = 1 AND bt.user_type_id = t.system_type_id
JOIN sys.tables st ON c.object_id = st.object_id
JOIN sys.schemas s ON st.schema_id = s.schema_id
WHERE s.name = @schema AND st.name = @table
ORDER BY c.column_id;
`

	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
	defer cancel()

	rows, err := db.QueryContext(ctx, query, sql.Named("schema", migrationJob.Schema), sql.Named("table", migrationJob.Table))
	if err != nil {
		return nil, fmt.Errorf("Error querying column types: %w", err)
	}
	defer rows.Close()

	var colTypes []ColumnType

	for rows.Next() {
		var column ColumnType

		if err := rows.Scan(
			&column.name,
			&column.userType,
			&column.systemType,
			&column.nullable,
			&column.maxLength,
			&column.precision,
			&column.scale,
		); err != nil {
			return nil, fmt.Errorf("Error scanning column type results: %W", err)
		}

		colTypes = append(colTypes, column)
	}

	return colTypes, nil
}

func queryTargetColTypes(db *pgxpool.Pool, migrationJob MigrationJob) ([]ColumnType, error) {
	query := `
SELECT 
  c.column_name AS name,
  c.data_type AS user_type,
  c.udt_name AS system_type,
  (CASE WHEN c.is_nullable = 'YES' THEN TRUE ELSE FALSE END) AS nullable,
  c.character_maximum_length AS max_length,
  c.numeric_precision AS precision,
  c.numeric_scale AS scale
FROM information_schema.columns c
WHERE c.table_schema = $1 AND c.table_name = $2
ORDER BY c.ordinal_position;
`

	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
	defer cancel()

	rows, err := db.Query(ctx, query, migrationJob.Schema, migrationJob.Table)
	if err != nil {
		return nil, fmt.Errorf("Error querying column types: %w", err)
	}
	defer rows.Close()

	var colTypes []ColumnType

	for rows.Next() {
		var column ColumnType
		var scanMaxLength *int64
		var scanPrecision *int64
		var scanScale *int64

		if err := rows.Scan(
			&column.name,
			&column.userType,
			&column.systemType,
			&column.nullable,
			&scanMaxLength,
			&scanPrecision,
			&scanScale,
		); err != nil {
			return nil, fmt.Errorf("Error scanning column type results: %w", err)
		}

		if scanMaxLength != nil {
			column.maxLength = *scanMaxLength
			column.hasMaxLength = true
		} else {
			column.maxLength = -1
		}

		if column.systemType == "decimal" {
			if scanPrecision != nil && scanScale != nil {
				column.precision = *scanPrecision
				column.scale = *scanScale
				column.hasPrecisionScale = true
			}
		}

		colTypes = append(colTypes, column)
	}

	return colTypes, nil
}

func queryColumnTypes(sourceDb *sql.DB, targetDb *pgxpool.Pool, migrationJob MigrationJob) ([]ColumnType, []ColumnType, error) {
	var sourceDbErr error
	var targetDbErr error
	var sourceColTypes []ColumnType
	var targetColTypes []ColumnType
	var wg sync.WaitGroup

	wg.Go(func() {
		sourceColTypes, sourceDbErr = querySourceColTypes(sourceDb, migrationJob)
		if sourceDbErr != nil {
			log.Error("Error (sourceDb): ", sourceDbErr)
		}
	})

	wg.Go(func() {
		targetColTypes, targetDbErr = queryTargetColTypes(targetDb, migrationJob)
		if targetDbErr != nil {
			log.Error("Error (targetDb): ", targetDbErr)
		}
	})

	wg.Wait()

	if sourceDbErr != nil || targetDbErr != nil {
		return nil, nil, errors.New("Error querying column types")
	}

	return sourceColTypes, targetColTypes, nil
}