package main

import (
	"context"
	"database/sql"
	"slices"
	"strings"
	"time"

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

type UnknownRowValues = []any

func extractFromMssql(
	ctx context.Context,
	db *sql.DB,
	job MigrationJob,
	columns []ColumnType,
	chunkSize int,
	chBatchesIn <-chan Batch,
	chChunksOut chan<- []UnknownRowValues,
	chErrorsOut chan<- ExtractorError,
	chJobErrorsOut chan<- JobError,
) {
	indexPrimaryKey := slices.IndexFunc(columns, func(col ColumnType) bool {
		return strings.EqualFold(col.name, job.PrimaryKey)
	})

	if indexPrimaryKey == -1 {
		jobError := JobError{
			ShouldCancelJob: true,
			Msg:             "Primary key not found in provided columns",
		}
		chJobErrorsOut <- jobError
		return
	}

	for batch := range chBatchesIn {
		func() {
			query := buildExtractQueryMssql(job, columns, batch.ShouldUseRange, batch.IsLowerLimitInclusive)
			log.Debug("Query used to extract data from mssql: ", query)

			var queryArgs []any
			if batch.ShouldUseRange {
				queryArgs = append(queryArgs,
					sql.Named("min", batch.LowerLimit),
					sql.Named("max", batch.UpperLimit),
				)
			}

			queryStartTime := time.Now()
			rows, err := db.QueryContext(ctx, query, queryArgs...)
			if err != nil {
				exError := ExtractorError{
					Batch:     batch,
					HasLastId: false,
					Msg:       err.Error(),
				}
				chErrorsOut <- exError
				return
			}
			defer rows.Close()
			log.Debugf("Query executed in %v", time.Since(queryStartTime))

			rowsChunk := make([]UnknownRowValues, 0, chunkSize)
			totalRowsExtracted := 0
			chunkStartTime := time.Now()

			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 {
					if len(rowsChunk) == 0 {
						exError := ExtractorError{
							Batch:     batch,
							HasLastId: false,
							Msg:       err.Error(),
						}
						chErrorsOut <- exError
						return
					}

					lastRow := rowsChunk[len(rowsChunk)-1]
					chChunksOut <- rowsChunk
					chErrorsOut <- ExtractorErrorFromLastRowMssql(lastRow, indexPrimaryKey, &batch, err)
					return
				}

				rowsChunk = append(rowsChunk, values)
				totalRowsExtracted++

				if len(rowsChunk) >= chunkSize {
					chunkDuration := time.Since(chunkStartTime)
					rowsPerSec := float64(chunkSize) / chunkDuration.Seconds()
					log.Infof("Extracted chunk: %d rows in %v (%.0f rows/sec) - Total: %d rows",
						len(rowsChunk), chunkDuration, rowsPerSec, totalRowsExtracted)
					chChunksOut <- rowsChunk
					rowsChunk = make([]UnknownRowValues, 0, chunkSize)
					chunkStartTime = time.Now()
				}
			}

			if len(rowsChunk) > 0 {
				chunkDuration := time.Since(chunkStartTime)
				rowsPerSec := float64(len(rowsChunk)) / chunkDuration.Seconds()
				log.Infof("Extracted final chunk: %d rows in %v (%.0f rows/sec) - Total: %d rows",
					len(rowsChunk), chunkDuration, rowsPerSec, totalRowsExtracted)
				chChunksOut <- rowsChunk
			}

			if err := rows.Err(); err != nil {
				if len(rowsChunk) == 0 {
					exError := ExtractorError{
						Batch:     batch,
						HasLastId: false,
						Msg:       err.Error(),
					}
					chErrorsOut <- exError
					return
				}

				lastRow := rowsChunk[len(rowsChunk)-1]
				chErrorsOut <- ExtractorErrorFromLastRowMssql(lastRow, indexPrimaryKey, &batch, err)
				return
			}
		}()
	}
}

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
}