package main

import (
	"context"
	"database/sql"

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

type UnknownRowValues = []any

func extractFromMssql(ctx context.Context, job MigrationJob, columns []ColumnType, chunkSize int, db *sql.DB, out chan<- []UnknownRowValues) error {
	query := buildExtractQueryMssql(job, columns)
	log.Debug("Query used to extract data from mssql: ", query)

	rows, err := db.QueryContext(ctx, query)
	if err != nil {
		return err
	}
	defer rows.Close()

	rowsChunk := make([]UnknownRowValues, 0, chunkSize)

	for rows.Next() {
		values := make([]any, len(columns))
		scanArgs := make([]any, len(columns))

		for i := range values {
			scanArgs[i] = &values[i]
		}

		if err := rows.Scan(scanArgs...); err != nil {
			return err
		}

		rowsChunk = append(rowsChunk, values)

		if len(rowsChunk) >= chunkSize {
			out <- rowsChunk
			rowsChunk = make([]UnknownRowValues, 0, chunkSize)
			log.Debugf("Chunk send... %+v", job)
		}
	}

	if len(rowsChunk) > 0 {
		out <- rowsChunk
		log.Debugf("Chunk send... %+v", job)
	}

	return nil
}

func extractFromPostgres(ctx context.Context, job MigrationJob, columns []ColumnType, chunkSize int, db *pgxpool.Pool, out chan<- []UnknownRowValues) error {
	query := buildExtractQueryPostgres(job, columns)
	log.Debug("Query used to extract data from postgres: ", query)

	rows, err := db.Query(ctx, query)
	if err != nil {
		return err
	}
	defer rows.Close()

	rowsChunk := make([]UnknownRowValues, 0, chunkSize)

	for rows.Next() {
		values, err := rows.Values()
		if err != nil {
			return err
		}

		rowsChunk = append(rowsChunk, values)

		if len(rowsChunk) >= chunkSize {
			out <- rowsChunk
			rowsChunk = make([]UnknownRowValues, 0, chunkSize)
			log.Infof("Chunk send... %+v", job)
		}
	}

	if len(rowsChunk) > 0 {
		out <- rowsChunk
		log.Infof("Chunk send... %+v", job)
	}

	return nil
}