package db_client

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/spf13/viper"
	"github.com/turbot/go-kit/helpers"
	"github.com/turbot/steampipe/pkg/constants"
	"github.com/turbot/steampipe/pkg/db/db_common"
	"github.com/turbot/steampipe/pkg/query/queryresult"
	"github.com/turbot/steampipe/pkg/statushooks"
	"github.com/turbot/steampipe/pkg/utils"
	"golang.org/x/text/language"
	"golang.org/x/text/message"
)

// ExecuteSync implements Client
// execute a query against this client and wait for the result
func (c *DbClient) ExecuteSync(ctx context.Context, query string) (*queryresult.SyncQueryResult, error) {
	// acquire a session
	sessionResult := c.AcquireSession(ctx)
	if sessionResult.Error != nil {
		return nil, sessionResult.Error
	}
	defer func() {
		// we need to do this in a closure, otherwise the ctx will be evaluated immediately
		// and not in call-time
		sessionResult.Session.Close(utils.IsContextCancelled(ctx))
	}()
	return c.ExecuteSyncInSession(ctx, sessionResult.Session, query)
}

// ExecuteSyncInSession implements Client
// execute a query against this client and wait for the result
func (c *DbClient) ExecuteSyncInSession(ctx context.Context, session *db_common.DatabaseSession, query string) (*queryresult.SyncQueryResult, error) {
	if query == "" {
		return &queryresult.SyncQueryResult{}, nil
	}

	result, err := c.ExecuteInSession(ctx, session, query, nil)
	if err != nil {
		return nil, err
	}
	syncResult := &queryresult.SyncQueryResult{ColTypes: result.ColTypes}
	for row := range *result.RowChan {
		select {
		case <-ctx.Done():
		default:
			syncResult.Rows = append(syncResult.Rows, row)
		}
	}
	if c.shouldShowTiming() {
		syncResult.TimingResult = <-result.TimingResult
	}
	return syncResult, nil
}

// Execute implements Client
// execute the query in the given Context
// NOTE: The returned Result MUST be fully read - otherwise the connection will block and will prevent further communication
func (c *DbClient) Execute(ctx context.Context, query string) (*queryresult.Result, error) {
	// acquire a session
	sessionResult := c.AcquireSession(ctx)
	if sessionResult.Error != nil {
		return nil, sessionResult.Error
	}
	// re-read ArgTiming from viper (in case the .timing command has been run)
	// (this will refetch ScanMetadataMaxId is timing has just been enabled)
	c.setShouldShowTiming(ctx, sessionResult.Session)

	// define callback to close session when the async execution is complete
	closeSessionCallback := func() { sessionResult.Session.Close(utils.IsContextCancelled(ctx)) }
	return c.ExecuteInSession(ctx, sessionResult.Session, query, closeSessionCallback)
}

// ExecuteInSession implements Client
// execute the query in the given Context using the provided DatabaseSession
// ExecuteInSession assumes no responsibility over the lifecycle of the DatabaseSession - that is the responsibility of the caller
// NOTE: The returned Result MUST be fully read - otherwise the connection will block and will prevent further communication
func (c *DbClient) ExecuteInSession(ctx context.Context, session *db_common.DatabaseSession, query string, onComplete func()) (res *queryresult.Result, err error) {
	if query == "" {
		return queryresult.NewQueryResult(nil), nil
	}

	// fail-safes
	if session == nil {
		return nil, fmt.Errorf("nil session passed to ExecuteInSession")
	}
	if session.Connection == nil {
		return nil, fmt.Errorf("nil database connection passed to ExecuteInSession")
	}
	startTime := time.Now()

	var tx *sql.Tx

	defer func() {
		if err != nil {
			// stop spinner in case of error
			statushooks.Done(ctx)
			// error - rollback transaction if we have one
			if tx != nil {
				tx.Rollback()
			}
			// in case of error call the onComplete callback
			if onComplete != nil {
				onComplete()
			}
		}
	}()

	statushooks.SetStatus(ctx, "Loading results...")

	// start query
	var rows *sql.Rows
	rows, err = c.startQuery(ctx, query, session.Connection)
	if err != nil {
		return
	}

	var colTypes []*sql.ColumnType
	colTypes, err = rows.ColumnTypes()
	if err != nil {
		err = fmt.Errorf("error reading columns from query: %v", err)
		return
	}

	result := queryresult.NewQueryResult(colTypes)

	// read the rows in a go routine
	go func() {
		// define a callback which fetches the timing information
		// this will be invoked after reading rows is complete but BEFORE closing the rows object (which closes the connection)
		timingCallback := func() {
			c.getQueryTiming(ctx, startTime, session, result.TimingResult)
		}

		// read in the rows and stream to the query result object
		c.readRows(ctx, rows, result, timingCallback)

		// call the completion callback - if one was provided
		if onComplete != nil {
			onComplete()
		}
	}()

	return result, nil
}

func (c *DbClient) getQueryTiming(ctx context.Context, startTime time.Time, session *db_common.DatabaseSession, resultChannel chan *queryresult.TimingResult) {
	if !c.shouldShowTiming() {
		return
	}

	var timingResult = &queryresult.TimingResult{
		Duration: time.Since(startTime),
	}
	// disable fetching timing information to avoid recursion
	c.disableTiming = true

	// whatever happens, we need to reenable timing, and send the result back with at least the duration
	defer func() {
		c.disableTiming = false
		resultChannel <- timingResult
	}()

	res, err := c.ExecuteSyncInSession(ctx, session, fmt.Sprintf("select id, rows_fetched, cache_hit, hydrate_calls from steampipe_command.scan_metadata where id > %d", session.ScanMetadataMaxId))
	// if we failed to read scan metadata (either because the query failed or the plugin does not support it)
	// just return
	if err != nil || len(res.Rows) == 0 {
		return
	}

	// so we have scan metadata - create the metadata struct
	timingResult.Metadata = &queryresult.TimingMetadata{}
	var id int64
	for _, r := range res.Rows {
		rw := r.(*queryresult.RowResult)
		id = rw.Data[0].(int64)
		rowsFetched := rw.Data[1].(int64)
		cacheHit := rw.Data[2].(bool)
		hydrateCalls := rw.Data[3].(int64)

		timingResult.Metadata.HydrateCalls += hydrateCalls
		if cacheHit {
			timingResult.Metadata.CachedRowsFetched += rowsFetched
		} else {
			timingResult.Metadata.RowsFetched += rowsFetched
		}

	}
	// update the max id for this session
	session.ScanMetadataMaxId = id

	return
}

func (c *DbClient) updateScanMetadataMaxId(ctx context.Context, session *db_common.DatabaseSession) error {
	res, err := c.ExecuteSyncInSession(ctx, session, "select max(id) from steampipe_command.scan_metadata")
	if err != nil {
		return err
	}

	for _, r := range res.Rows {
		rw := r.(*queryresult.RowResult)
		id, ok := rw.Data[0].(int64)
		if ok {
			// update the max id for this session
			session.ScanMetadataMaxId = id
		}

		break
	}
	return nil
}

// run query in a goroutine, so we can check for cancellation
// in case the client becomes unresponsive and does not respect context cancellation
func (c *DbClient) startQuery(ctx context.Context, query string, conn *sql.Conn) (rows *sql.Rows, err error) {
	doneChan := make(chan bool)
	defer func() {
		if err != nil {
			if errors.Is(err, context.DeadlineExceeded) {
				// if the context deadline has been exceeded, call refreshDbClient to create a new SQL client
				// this will refresh the session data which will have been cleared by the SQL client error handling
				c.refreshDbClient(context.Background())
			}
		}
	}()
	go func() {
		// start asynchronous query
		rows, err = conn.QueryContext(ctx, query)
		close(doneChan)
	}()

	select {
	case <-doneChan:
	case <-ctx.Done():
		err = ctx.Err()
	}
	return
}

func (c *DbClient) readRows(ctx context.Context, rows *sql.Rows, result *queryresult.Result, timingCallback func()) {
	// defer this, so that these get cleaned up even if there is an unforeseen error
	defer func() {
		// we are done fetching results. time for display. clear the status indication
		statushooks.Done(ctx)
		// call the timing callback BEFORE closing the rows
		timingCallback()
		// close the sql rows object
		rows.Close()
		if err := rows.Err(); err != nil {
			result.StreamError(err)
		}
		// close the channels in the result object
		result.Close()

	}()

	rowCount := 0
	colTypes, err := rows.ColumnTypes()
	if err != nil {
		// we do not need to stream because
		// defer takes care of it!
		return
	}
	cols, err := rows.Columns()
	if err != nil {
		// we do not need to stream because
		// defer takes care of it!
		return
	}

	for rows.Next() {
		continueToNext := true
		select {
		case <-ctx.Done():
			statushooks.SetStatus(ctx, "Cancelling query")
			continueToNext = false
		default:
			if rowResult, err := readRowContext(ctx, rows, cols, colTypes); err != nil {
				result.StreamError(err)
				continueToNext = false
			} else {
				// TACTICAL
				// determine whether to stop the spinner as soon as we stream a row or to wait for completion
				if isStreamingOutput(viper.GetString(constants.ArgOutput)) {
					statushooks.Done(ctx)
				}

				result.StreamRow(rowResult)
			}
			// update the status message with the count of rows that have already been fetched
			// this will not show if the spinner is not active
			statushooks.SetStatus(ctx, fmt.Sprintf("Loading results: %3s", humanizeRowCount(rowCount)))
			rowCount++
		}
		if !continueToNext {
			break
		}
	}
}

func isStreamingOutput(outputFormat string) bool {
	return helpers.StringSliceContains([]string{constants.OutputFormatCSV, constants.OutputFormatLine}, outputFormat)
}

func readRowContext(ctx context.Context, rows *sql.Rows, cols []string, colTypes []*sql.ColumnType) ([]interface{}, error) {
	c := make(chan bool, 1)
	var readRowResult []interface{}
	var readRowError error
	go func() {
		readRowResult, readRowError = readRow(rows, cols, colTypes)
		close(c)
	}()

	select {
	case <-ctx.Done():
		return nil, ctx.Err()
	case <-c:
		return readRowResult, readRowError
	}

}

func readRow(rows *sql.Rows, cols []string, colTypes []*sql.ColumnType) ([]interface{}, error) {
	// slice of interfaces to receive the row data
	columnValues := make([]interface{}, len(cols))
	// make a slice of pointers to the result to pass to scan
	resultPtrs := make([]interface{}, len(cols)) // A temporary interface{} slice
	for i := range columnValues {
		resultPtrs[i] = &columnValues[i]
	}
	err := rows.Scan(resultPtrs...)
	if err != nil {
		// return error, handling cancellation error explicitly
		return nil, utils.HandleCancelError(err)
	}
	return populateRow(columnValues, colTypes)
}

func populateRow(columnValues []interface{}, colTypes []*sql.ColumnType) ([]interface{}, error) {
	result := make([]interface{}, len(columnValues))
	for i, columnValue := range columnValues {
		if columnValue != nil {
			colType := colTypes[i]
			dbType := colType.DatabaseTypeName()
			switch dbType {
			case "JSON", "JSONB":
				var val interface{}
				if err := json.Unmarshal(columnValue.([]byte), &val); err != nil {
					return result, err
				}
				result[i] = val
			default:
				result[i] = columnValue
			}
		}
	}
	return result, nil
}

func humanizeRowCount(count int) string {
	p := message.NewPrinter(language.English)
	return p.Sprintf("%d", count)
}