package main

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

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

func fakeLoader(job MigrationJob, columns []ColumnType, in <-chan [][]any) {

	for rows := range in {
		log.Debugf("Chunk received, loading data into...")

		for i, rowValues := range rows {
			if i%100 == 0 {
				logSampleRow(job, columns, rowValues, fmt.Sprintf("row %d", i))
			}
		}
	}
}

func loadRowsPostgres(ctx context.Context, job MigrationJob, columns []ColumnType, db *pgxpool.Pool, in <-chan []UnknownRowValues) error {
	chunkCount := 0
	totalRowsLoaded := 0

	for rows := range in {
		chunkStartTime := time.Now()
		identifier := pgx.Identifier{job.Schema, job.Table}
		colNames := Map(columns, func(col ColumnType) string {
			return col.name
		})

		copyStartTime := time.Now()
		_, err := db.CopyFrom(
			ctx,
			identifier,
			colNames,
			pgx.CopyFromRows(rows),
		)

		if err != nil {
			return err
		}

		chunkCount++
		totalRowsLoaded += len(rows)
		copyDuration := time.Since(copyStartTime)
		chunkDuration := time.Since(chunkStartTime)
		rowsPerSec := float64(len(rows)) / chunkDuration.Seconds()

		log.Infof("Loaded chunk #%d: %d rows in %v (copy: %v, %.0f rows/sec) - Total: %d rows", chunkCount, len(rows), chunkDuration, copyDuration, rowsPerSec, totalRowsLoaded)
	}

	return nil
}

func loadRowsMssql(ctx context.Context, job MigrationJob, columns []ColumnType, db *sql.DB, in <-chan []UnknownRowValues) error {
	chunkCount := 0
	totalRowsLoaded := 0

	for rows := range in {
		chunkStartTime := time.Now()

		tx, err := db.BeginTx(ctx, nil)
		if err != nil {
			return fmt.Errorf("error starting transaction: %w", err)
		}

		fullTableName := fmt.Sprintf("[%s].[%s]", job.Schema, job.Table)
		colNames := Map(columns, func(col ColumnType) string {
			return col.name
		})

		stmt, err := tx.PrepareContext(ctx, mssql.CopyIn(fullTableName, mssql.BulkOptions{}, colNames...))
		if err != nil {
			tx.Rollback()
			return fmt.Errorf("error preparing bulk copy statement: %w", err)
		}

		copyStartTime := time.Now()

		for _, row := range rows {
			_, err = stmt.ExecContext(ctx, row...)
			if err != nil {
				stmt.Close()
				tx.Rollback()
				return fmt.Errorf("error executing row insert: %w", err)
			}
		}

		result, err := stmt.ExecContext(ctx)
		if err != nil {
			stmt.Close()
			tx.Rollback()
			return fmt.Errorf("error flushing bulk data: %w", err)
		}

		err = stmt.Close()
		if err != nil {
			tx.Rollback()
			return fmt.Errorf("error closing statement: %w", err)
		}

		if err := tx.Commit(); err != nil {
			return fmt.Errorf("error committing transaction: %w", err)
		}

		rowsAffected, _ := result.RowsAffected()
		chunkCount++
		totalRowsLoaded += int(rowsAffected)

		copyDuration := time.Since(copyStartTime)
		chunkDuration := time.Since(chunkStartTime)
		rowsPerSec := float64(len(rows)) / chunkDuration.Seconds()

		log.Infof("Loaded chunk #%d (MSSQL): %d rows in %v (copy: %v, %.0f rows/sec) - Total: %d rows", chunkCount, len(rows), chunkDuration, copyDuration, rowsPerSec, totalRowsLoaded)
	}

	return nil
}

func Map[T any, V any](input []T, mapper func(T) V) []V {
	result := make([]V, len(input))

	for i, v := range input {
		result[i] = mapper(v)
	}

	return result
}