// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package saphanareceiver // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/saphanareceiver"

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

	sapdriver "github.com/SAP/go-hdb/driver"
	"go.opentelemetry.io/collector/receiver/scrapererror"
)

// Interface for a SAP HANA client. Implementation can be faked for testing.
type client interface {
	Connect(ctx context.Context) error
	collectDataFromQuery(ctx context.Context, query *monitoringQuery) ([]map[string]string, error)
	Close() error
}

// Wraps the result of a query so that it can be mocked in tests
type resultWrapper interface {
	Scan(dest ...any) error
	Close() error
	Next() bool
}

// Wraps the sqlDB interface so that it can be mocked in tests
type dbWrapper interface {
	PingContext(ctx context.Context) error
	Close() error
	QueryContext(ctx context.Context, query string) (resultWrapper, error)
}

type standardResultWrapper struct {
	rows *sql.Rows
}

func (w *standardResultWrapper) Next() bool {
	return w.rows.Next()
}

func (w *standardResultWrapper) Scan(dest ...any) error {
	return w.rows.Scan(dest...)
}

func (w *standardResultWrapper) Close() error {
	return w.rows.Close()
}

type standardDBWrapper struct {
	db *sql.DB
}

func (w *standardDBWrapper) Close() error {
	return w.db.Close()
}

func (w *standardDBWrapper) PingContext(ctx context.Context) error {
	return w.db.PingContext(ctx)
}

func (w *standardDBWrapper) QueryContext(ctx context.Context, query string) (resultWrapper, error) {
	rows, err := w.db.QueryContext(ctx, query)
	if err != nil {
		return nil, err
	}
	resultWrapper := standardResultWrapper{rows}
	return &resultWrapper, nil
}

// Wraps the creation of a sqlDB so that it can be mocked in tests
type sapHanaConnectionFactory interface {
	getConnection(c driver.Connector) dbWrapper
}

type defaultConnectionFactory struct{}

func (f *defaultConnectionFactory) getConnection(c driver.Connector) dbWrapper {
	wrapper := standardDBWrapper{db: sql.OpenDB((c))}
	return &wrapper
}

// Wraps a SAP HANA database connection, implements `client` interface.
type sapHanaClient struct {
	receiverConfig    *Config
	connectionFactory sapHanaConnectionFactory
	client            dbWrapper
}

var _ client = (*sapHanaClient)(nil)

// Creates a SAP HANA database client
func newSapHanaClient(cfg *Config, factory sapHanaConnectionFactory) client {
	return &sapHanaClient{
		receiverConfig:    cfg,
		connectionFactory: factory,
	}
}

func (c *sapHanaClient) Connect(ctx context.Context) error {
	connector, err := sapdriver.NewDSNConnector(fmt.Sprintf("hdb://%s:%s@%s", c.receiverConfig.Username, c.receiverConfig.Password, c.receiverConfig.TCPAddr.Endpoint))
	if err != nil {
		return fmt.Errorf("error generating DSN for SAP HANA connection: %w", err)
	}

	tls, err := c.receiverConfig.TLSClientSetting.LoadTLSConfig()
	if err != nil {
		return fmt.Errorf("error generating TLS config for SAP HANA connection: %w", err)
	}
	connector.SetTLSConfig(tls)
	connector.SetApplicationName("OpenTelemetry Collector")

	client := c.connectionFactory.getConnection(connector)

	err = client.PingContext(ctx)
	if err == nil {
		c.client = client
	} else {
		client.Close()
	}

	return err
}

func (c *sapHanaClient) Close() error {
	if c.client != nil {
		client := c.client
		c.client = nil
		return client.Close()
	}
	return nil
}

func (c *sapHanaClient) collectDataFromQuery(ctx context.Context, query *monitoringQuery) ([]map[string]string, error) {
	rows, err := c.client.QueryContext(ctx, query.query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	errors := scrapererror.ScrapeErrors{}
	var data []map[string]string

ROW_ITERATOR:
	for rows.Next() {
		expectedFields := len(query.orderedMetricLabels) + len(query.orderedResourceLabels) + len(query.orderedStats)
		rowFields := make([]any, expectedFields)

		// Build a list of addresses that rows.Scan will load column data into
		for i := range rowFields {
			rowFields[i] = new(sql.NullString)
		}

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

		values := map[string]string{}
		for _, label := range query.orderedResourceLabels {
			v, err := convertInterfaceToString(rowFields[0])
			if err != nil {
				errors.AddPartial(0, err)
				continue ROW_ITERATOR
			}
			// If value was null, we can't use this row
			if !v.Valid {
				errors.AddPartial(0, fmt.Errorf("database row NULL value for required resource label %s", label))
				continue ROW_ITERATOR
			}
			values[label] = v.String
			rowFields = rowFields[1:]
		}
		for _, label := range query.orderedMetricLabels {
			v, err := convertInterfaceToString(rowFields[0])
			if err != nil {
				errors.AddPartial(0, err)
				continue ROW_ITERATOR
			}
			// If value was null, we can't use this row
			if !v.Valid {
				errors.AddPartial(0, fmt.Errorf("database row NULL value for required metric label %s", label))
				continue ROW_ITERATOR
			}
			values[label] = v.String
			rowFields = rowFields[1:]
		}
		for _, stat := range query.orderedStats {
			v, err := convertInterfaceToString(rowFields[0])
			if err != nil {
				errors.AddPartial(0, err)
				continue
			}
			// Only report stat if value was not NULL
			if v.Valid {
				values[stat.key] = v.String
			}
			rowFields = rowFields[1:]
		}

		data = append(data, values)
	}
	return data, errors.Combine()
}

func convertInterfaceToString(input any) (sql.NullString, error) {
	if val, ok := input.(*sql.NullString); ok {
		return *val, nil
	}
	return sql.NullString{}, errors.New("issue converting interface into string")
}