package sql

import (
	"context"
	"fmt"
	"net/http"
	"os"
	"sync"
	"time"

	"github.com/fullstorydev/grpchan/inprocgrpc"
	"github.com/google/uuid"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"

	"github.com/grafana/grafana-app-sdk/logging"

	"github.com/grafana/grafana/pkg/apimachinery/utils"
	"github.com/grafana/grafana/pkg/storage/unified/parquet"
	"github.com/grafana/grafana/pkg/storage/unified/resource"
	"github.com/grafana/grafana/pkg/storage/unified/resourcepb"
	"github.com/grafana/grafana/pkg/storage/unified/sql/db"
	"github.com/grafana/grafana/pkg/storage/unified/sql/db/dbimpl"
	"github.com/grafana/grafana/pkg/storage/unified/sql/dbutil"
	"github.com/grafana/grafana/pkg/storage/unified/sql/sqltemplate"
)

var (
	_ resource.BulkProcessingBackend = (*backend)(nil)
)

type bulkRV struct {
	max     int64
	counter int64
}

// When executing a bulk import we can fake the RV values
func newBulkRV() *bulkRV {
	t := time.Now().Truncate(time.Second * 10)
	return &bulkRV{
		max:     (t.UnixMicro() / 10000000) * 10000000,
		counter: 0,
	}
}

func (x *bulkRV) next(obj metav1.Object) int64 {
	ts := obj.GetCreationTimestamp().UnixMicro()
	anno := obj.GetAnnotations()
	if anno != nil {
		v := anno[utils.AnnoKeyUpdatedTimestamp]
		t, err := time.Parse(time.RFC3339, v)
		if err == nil {
			ts = t.UnixMicro()
		}
	}
	if ts > x.max || ts < 10000000 {
		ts = x.max
	}
	x.counter++
	return (ts/10000000)*10000000 + x.counter
}

type bulkLock struct {
	running map[string]bool
	mu      sync.Mutex
}

func (x *bulkLock) Start(keys []*resourcepb.ResourceKey) error {
	x.mu.Lock()
	defer x.mu.Unlock()

	// First verify that it is not already running
	ids := make([]string, len(keys))
	for i, k := range keys {
		id := resource.NSGR(k)
		if x.running[id] {
			return &apierrors.StatusError{ErrStatus: metav1.Status{
				Code:    http.StatusPreconditionFailed,
				Message: "bulk export is already running",
			}}
		}
		ids[i] = id
	}

	// Then add the keys to the lock
	for _, k := range ids {
		x.running[k] = true
	}
	return nil
}

func (x *bulkLock) Finish(keys []*resourcepb.ResourceKey) {
	x.mu.Lock()
	defer x.mu.Unlock()
	for _, k := range keys {
		delete(x.running, resource.NSGR(k))
	}
}

func (x *bulkLock) Active() bool {
	x.mu.Lock()
	defer x.mu.Unlock()
	return len(x.running) > 0
}

func (b *backend) ProcessBulk(ctx context.Context, setting resource.BulkSettings, iter resource.BulkRequestIterator) *resourcepb.BulkResponse {
	err := b.bulkLock.Start(setting.Collection)
	if err != nil {
		return &resourcepb.BulkResponse{
			Error: resource.AsErrorResult(err),
		}
	}
	defer b.bulkLock.Finish(setting.Collection)

	// If provided, reuse the inproc transaction for SQLite
	if clientCtx := inprocgrpc.ClientContext(ctx); clientCtx != nil && b.dialect.DialectName() == "sqlite" {
		if externalTx := resource.TransactionFromContext(clientCtx); externalTx != nil {
			b.log.Info("Using SQLite transaction from client context")
			rsp := &resourcepb.BulkResponse{}
			err := b.processBulkWithTx(ctx, dbimpl.NewTx(externalTx), setting, iter, rsp)
			if err != nil {
				rsp.Error = resource.AsErrorResult(err)
			}
			return rsp
		}
	}

	// We may want to first write parquet, then read parquet
	if b.dialect.DialectName() == "sqlite" {
		file, err := os.CreateTemp("", "grafana-bulk-export-*.parquet")
		if err != nil {
			return &resourcepb.BulkResponse{
				Error: resource.AsErrorResult(err),
			}
		}

		writer, err := parquet.NewParquetWriter(file)
		if err != nil {
			return &resourcepb.BulkResponse{
				Error: resource.AsErrorResult(err),
			}
		}

		// write bulk to parquet
		rsp := writer.ProcessBulk(ctx, setting, iter)
		if rsp.Error != nil {
			return rsp
		}

		b.log.Info("using parquet buffer", "parquet", file)

		// Replace the iterator with one from parquet
		iter, err = parquet.NewParquetReader(file.Name(), 50)
		if err != nil {
			return &resourcepb.BulkResponse{
				Error: resource.AsErrorResult(err),
			}
		}
	}

	return b.processBulk(ctx, setting, iter)
}

// internal bulk process
func (b *backend) processBulk(ctx context.Context, setting resource.BulkSettings, iter resource.BulkRequestIterator) *resourcepb.BulkResponse {
	rsp := &resourcepb.BulkResponse{}
	err := b.db.WithTx(ctx, ReadCommitted, func(ctx context.Context, tx db.Tx) error {
		return b.processBulkWithTx(ctx, tx, setting, iter, rsp)
	})
	if err != nil {
		rsp.Error = resource.AsErrorResult(err)
	}
	return rsp
}

// processBulkWithTx performs the bulk operation using the provided transaction.
// This is used both when creating our own transaction and when reusing an external one.
func (b *backend) processBulkWithTx(ctx context.Context, tx db.Tx, setting resource.BulkSettings, iter resource.BulkRequestIterator, rsp *resourcepb.BulkResponse) error {
	rollbackWithError := func(err error) error {
		txerr := tx.Rollback()
		if txerr != nil {
			b.log.Warn("rollback", "error", txerr)
		} else {
			b.log.Info("rollback")
		}
		return err
	}
	bulk := &bulkWroker{
		ctx:     ctx,
		tx:      tx,
		dialect: b.dialect,
		logger:  logging.FromContext(ctx),
	}

	// Calculate the RV based on incoming request timestamps
	rv := newBulkRV()

	summaries := make(map[string]*resourcepb.BulkResponse_Summary, len(setting.Collection))

	// First clear everything in the transaction
	if setting.RebuildCollection {
		for _, key := range setting.Collection {
			summary, err := bulk.deleteCollection(key)
			if err != nil {
				return rollbackWithError(err)
			}
			summaries[resource.NSGR(key)] = summary
			rsp.Summary = append(rsp.Summary, summary)
		}
	} else {
		for _, key := range setting.Collection {
			summaries[resource.NSGR(key)] = &resourcepb.BulkResponse_Summary{
				Namespace: key.Namespace,
				Group:     key.Group,
				Resource:  key.Resource,
			}
		}
	}

	obj := &unstructured.Unstructured{}

	// Write each event into the history
	for iter.Next() {
		if iter.RollbackRequested() {
			return rollbackWithError(nil)
		}
		req := iter.Request()
		if req == nil {
			return rollbackWithError(fmt.Errorf("missing request"))
		}
		rsp.Processed++

		if req.Action == resourcepb.BulkRequest_UNKNOWN {
			rsp.Rejected = append(rsp.Rejected, &resourcepb.BulkResponse_Rejected{
				Key:    req.Key,
				Action: req.Action,
				Error:  "unknown action",
			})
			continue
		}

		err := obj.UnmarshalJSON(req.Value)
		if err != nil {
			rsp.Rejected = append(rsp.Rejected, &resourcepb.BulkResponse_Rejected{
				Key:    req.Key,
				Action: req.Action,
				Error:  "unable to unmarshal json",
			})
			continue
		}

		// Write the event to history
		if _, err := dbutil.Exec(ctx, tx, sqlResourceHistoryInsert, sqlResourceRequest{
			SQLTemplate: sqltemplate.New(b.dialect),
			WriteEvent: resource.WriteEvent{
				Key:        req.Key,
				Type:       resourcepb.WatchEvent_Type(req.Action),
				Value:      req.Value,
				PreviousRV: -1, // Used for WATCH, but we want to skip watch events
			},
			Folder:          req.Folder,
			GUID:            uuid.New().String(),
			ResourceVersion: rv.next(obj),
		}); err != nil {
			return rollbackWithError(fmt.Errorf("insert into resource history: %w", err))
		}
	}

	// Now update the resource table from history
	for _, key := range setting.Collection {
		k := fmt.Sprintf("%s/%s/%s", key.Namespace, key.Group, key.Resource)
		summary := summaries[k]
		if summary == nil {
			return rollbackWithError(fmt.Errorf("missing summary key for: %s", k))
		}

		err := bulk.syncCollection(key, summary)
		if err != nil {
			return err
		}

		if b.dialect.DialectName() == "sqlite" {
			nextRV, err := b.rvManager.Lock(ctx, tx, key.Group, key.Resource)
			if err != nil {
				b.log.Error("error locking RV", "error", err, "key", resource.NSGR(key))
			} else {
				b.log.Info("successfully locked RV", "nextRV", nextRV, "key", resource.NSGR(key))
				// Save the incremented RV
				if err := b.rvManager.SaveRV(ctx, tx, key.Group, key.Resource, nextRV); err != nil {
					b.log.Error("error saving RV", "error", err, "key", resource.NSGR(key))
				} else {
					b.log.Info("successfully saved RV", "rv", nextRV, "key", resource.NSGR(key))
				}
			}
		} else {
			// Make sure the collection RV is above our last written event
			_, err = b.rvManager.ExecWithRV(ctx, key, func(tx db.Tx) (string, error) {
				return "", nil
			})
			if err != nil {
				b.log.Warn("error increasing RV", "error", err)
			}
		}

		// Update the last import time. This is important to trigger reindexing
		// of the resource for a given namespace.
		if err := b.updateLastImportTime(ctx, tx, key, time.Now()); err != nil {
			return rollbackWithError(err)
		}
	}
	return nil
}

func (b *backend) updateLastImportTime(ctx context.Context, tx db.Tx, key *resourcepb.ResourceKey, now time.Time) error {
	if _, err := dbutil.Exec(ctx, tx, sqlResourceLastImportTimeInsert, sqlResourceLastImportTimeInsertRequest{
		SQLTemplate:    sqltemplate.New(b.dialect),
		Namespace:      key.Namespace,
		Group:          key.Group,
		Resource:       key.Resource,
		LastImportTime: now.UTC(),
	}); err != nil {
		return fmt.Errorf("insert resource last import time: %w", err)
	}
	return nil
}

type bulkWroker struct {
	ctx     context.Context
	tx      db.ContextExecer
	dialect sqltemplate.Dialect
	logger  logging.Logger
}

// This will remove everything from the `resource` and `resource_history` table for a given namespace/group/resource
func (w *bulkWroker) deleteCollection(key *resourcepb.ResourceKey) (*resourcepb.BulkResponse_Summary, error) {
	summary := &resourcepb.BulkResponse_Summary{
		Namespace: key.Namespace,
		Group:     key.Group,
		Resource:  key.Resource,
	}

	// First delete history
	res, err := dbutil.Exec(w.ctx, w.tx, sqlResourceHistoryDelete, &sqlResourceHistoryDeleteRequest{
		SQLTemplate: sqltemplate.New(w.dialect),
		Namespace:   key.Namespace,
		Group:       key.Group,
		Resource:    key.Resource,
	})
	if err != nil {
		return nil, err
	}

	summary.PreviousHistory, err = res.RowsAffected()
	if err != nil {
		return nil, err
	}

	// Next delete the active resource table
	res, err = dbutil.Exec(w.ctx, w.tx, sqlResourceDelete, &sqlResourceRequest{
		SQLTemplate: sqltemplate.New(w.dialect),
		WriteEvent: resource.WriteEvent{
			Key: key,
		},
	})
	if err != nil {
		return nil, err
	}
	summary.PreviousCount, err = res.RowsAffected()
	return summary, err
}

// Copy the latest value from history into the active resource table
func (w *bulkWroker) syncCollection(key *resourcepb.ResourceKey, summary *resourcepb.BulkResponse_Summary) error {
	w.logger.Info("synchronize collection", "key", resource.NSGR(key))
	_, err := dbutil.Exec(w.ctx, w.tx, sqlResourceInsertFromHistory, &sqlResourceInsertFromHistoryRequest{
		SQLTemplate: sqltemplate.New(w.dialect),
		Key:         key,
	})
	if err != nil {
		return err
	}

	w.logger.Info("get stats (still in transaction)", "key", resource.NSGR(key))
	rows, err := dbutil.QueryRows(w.ctx, w.tx, sqlResourceStats, &sqlStatsRequest{
		SQLTemplate: sqltemplate.New(w.dialect),
		Namespace:   key.Namespace,
		Group:       key.Group,
		Resource:    key.Resource,
	})
	if err != nil {
		return err
	}
	if rows != nil {
		defer func() {
			_ = rows.Close()
		}()
	}
	if rows.Next() {
		row := resource.ResourceStats{}
		return rows.Scan(&row.Namespace, &row.Group, &row.Resource,
			&summary.Count,
			&summary.ResourceVersion)
	}
	return err
}