package postgres

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

	"github.com/pkg/errors"
	"google.golang.org/protobuf/encoding/protojson"

	"github.com/usememos/memos/store"
)

// ApplyMemoMutation atomically updates a memo, attachment bindings, and reference relations.
func (d *DB) ApplyMemoMutation(ctx context.Context, mutation *store.MemoMutation) error {
	tx, err := d.db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
	if err != nil {
		return errors.Wrap(err, "failed to begin memo transaction")
	}
	defer func() {
		_ = tx.Rollback()
	}()
	if err := validatePostgresMemoRelationEndpoints(ctx, tx, mutation); err != nil {
		return err
	}
	if create := mutation.MemoCreate; create != nil {
		if err := validatePostgresMemoCreate(ctx, tx, create); err != nil {
			return err
		}
		if mutation.CommentContextMemoID != nil {
			if err := authorizePostgresMemoComment(ctx, tx, *mutation.CommentContextMemoID, create.CreatorID); err != nil {
				return err
			}
		}
		if err := insertPostgresMemo(ctx, tx, create); err != nil {
			return err
		}
		mutation.MemoID = create.ID
		mutation.MemoCreatorID = create.CreatorID
		mutation.ExpectedMemoContent = create.Content
		for _, relation := range mutation.ReferenceRelations {
			if relation != nil {
				relation.MemoID = create.ID
			}
		}
		if mutation.CommentContextMemoID != nil {
			if err := insertPostgresMemoCommentRelation(ctx, tx, create.ID, *mutation.CommentContextMemoID); err != nil {
				return err
			}
		}
	}
	policy := mutation.Policy
	if policy == nil && mutation.MemoUpdate != nil {
		policy = mutation.MemoUpdate.Policy
	}
	if policy != nil {
		if err := validatePostgresMemoWritePolicy(ctx, tx, mutation.MemoID, policy, mutation.MemoUpdate); err != nil {
			return err
		}
	}

	var creatorID int32
	var content string
	if err := tx.QueryRowContext(ctx, `SELECT creator_id, content FROM memo WHERE id = $1 FOR UPDATE`, mutation.MemoID).Scan(&creatorID, &content); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return errors.Wrap(store.ErrMemoMutationConflict, "memo no longer exists")
		}
		return errors.Wrap(err, "failed to lock memo")
	}
	if creatorID != mutation.MemoCreatorID || content != mutation.ExpectedMemoContent {
		return errors.Wrap(store.ErrMemoMutationConflict, "memo changed while applying mutation")
	}
	removedAttachments, err := listPostgresAttachmentSnapshots(ctx, tx, mutation.RemovedAttachmentIDs)
	if err != nil {
		return errors.Wrap(err, "failed to read removed attachments")
	}
	if len(removedAttachments) != len(mutation.RemovedAttachmentIDs) {
		return errors.Wrap(store.ErrMemoMutationConflict, "removed attachment no longer exists")
	}
	for _, attachment := range removedAttachments {
		if attachment.CreatorID != mutation.MemoCreatorID || attachment.MemoID == nil || *attachment.MemoID != mutation.MemoID {
			return errors.Wrap(store.ErrMemoMutationConflict, "attachment is no longer removable from the memo")
		}
	}

	for _, binding := range mutation.Bindings {
		var attachmentCreatorID int32
		var memoID sql.NullInt32
		if err := tx.QueryRowContext(ctx, `SELECT creator_id, memo_id FROM attachment WHERE id = $1 FOR UPDATE`, binding.ID).Scan(&attachmentCreatorID, &memoID); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.Wrapf(store.ErrMemoMutationConflict, "attachment %s no longer exists", binding.UID)
			}
			return errors.Wrap(err, "failed to lock attachment")
		}
		if binding.WasBoundToMemo {
			if !memoID.Valid || memoID.Int32 != mutation.MemoID {
				return errors.Wrapf(store.ErrMemoMutationConflict, "attachment %s is no longer bound to the memo", binding.UID)
			}
		} else if attachmentCreatorID != mutation.MemoCreatorID || memoID.Valid {
			return errors.Wrapf(store.ErrMemoMutationConflict, "attachment %s is no longer available", binding.UID)
		}
		if _, err := tx.ExecContext(ctx, `UPDATE attachment SET memo_id = $1, updated_ts = $2 WHERE id = $3`, mutation.MemoID, binding.UpdatedTs, binding.ID); err != nil {
			return errors.Wrap(err, "failed to bind attachment")
		}
	}
	for _, attachment := range removedAttachments {
		result, err := tx.ExecContext(ctx, `DELETE FROM attachment WHERE id = $1 AND memo_id = $2`, attachment.ID, mutation.MemoID)
		if err != nil {
			return errors.Wrap(err, "failed to delete removed attachment")
		}
		if rows, err := result.RowsAffected(); err != nil {
			return errors.Wrap(err, "failed to count deleted removed attachment")
		} else if rows != 1 {
			return errors.Wrap(store.ErrMemoMutationConflict, "attachment is no longer bound to the memo")
		}
	}

	for _, attachmentID := range mutation.RequiredAttachmentIDs {
		var exists int
		if err := tx.QueryRowContext(ctx, `SELECT 1 FROM attachment WHERE id = $1 AND memo_id = $2 FOR UPDATE`, attachmentID, mutation.MemoID).Scan(&exists); err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				return errors.Wrap(store.ErrMemoMutationConflict, "a referenced attachment is no longer bound to the memo")
			}
			return errors.Wrap(err, "failed to verify referenced attachment")
		}
	}

	if mutation.MemoUpdate != nil {
		if mutation.MemoUpdate.ID != mutation.MemoID {
			return errors.New("memo update target does not match attachment mutation")
		}
		if err := applyMemoUpdate(ctx, tx, mutation.MemoUpdate); err != nil {
			return err
		}
	}
	if mutation.ReplaceReferenceRelations {
		if err := replaceMemoReferenceRelations(ctx, tx, mutation.MemoID, mutation.ReferenceRelations); err != nil {
			return err
		}
	}
	if err := tx.Commit(); err != nil {
		return errors.Wrap(err, "failed to commit memo transaction")
	}
	return nil
}

func insertPostgresMemoCommentRelation(ctx context.Context, tx *sql.Tx, memoID, contextMemoID int32) error {
	if memoID <= 0 || contextMemoID <= 0 || memoID == contextMemoID {
		return errors.New("invalid COMMENT relation")
	}
	if _, err := tx.ExecContext(ctx, `INSERT INTO memo_relation (memo_id, related_memo_id, type) VALUES ($1, $2, $3)`,
		memoID, contextMemoID, store.MemoRelationComment); err != nil {
		return errors.Wrap(err, "failed to insert COMMENT relation")
	}
	return nil
}

func replaceMemoReferenceRelations(ctx context.Context, tx *sql.Tx, memoID int32, relations []*store.MemoRelation) error {
	if _, err := tx.ExecContext(ctx, `DELETE FROM memo_relation WHERE memo_id = $1 AND type = $2`, memoID, store.MemoRelationReference); err != nil {
		return errors.Wrap(err, "failed to delete memo reference relations")
	}
	for _, relation := range relations {
		if relation == nil || relation.MemoID != memoID || relation.Type != store.MemoRelationReference {
			return errors.New("invalid memo reference relation mutation")
		}
		if _, err := tx.ExecContext(ctx, `
			INSERT INTO memo_relation (memo_id, related_memo_id, type)
			VALUES ($1, $2, $3)
			ON CONFLICT (memo_id, related_memo_id, type) DO UPDATE SET type = EXCLUDED.type
		`, relation.MemoID, relation.RelatedMemoID, relation.Type); err != nil {
			return errors.Wrap(err, "failed to insert memo reference relation")
		}
	}
	return nil
}

type memoUpdateExecer interface {
	ExecContext(context.Context, string, ...any) (sql.Result, error)
}

func applyMemoUpdate(ctx context.Context, executor memoUpdateExecer, update *store.UpdateMemo) error {
	set, args := []string{}, []any{}
	appendValue := func(column string, value any) {
		args = append(args, value)
		set = append(set, column+" = "+placeholder(len(args)))
	}
	if v := update.UID; v != nil {
		appendValue("uid", *v)
	}
	if v := update.CreatedTs; v != nil {
		appendValue("created_ts", *v)
	}
	if v := update.UpdatedTs; v != nil {
		appendValue("updated_ts", *v)
	}
	if v := update.RowStatus; v != nil {
		appendValue("row_status", *v)
	}
	if v := update.Content; v != nil {
		appendValue("content", *v)
	}
	if v := update.Visibility; v != nil {
		appendValue("visibility", *v)
	}
	if v := update.Pinned; v != nil {
		appendValue("pinned", *v)
	}
	if v := update.Payload; v != nil {
		payload, err := protojson.Marshal(v)
		if err != nil {
			return errors.Wrap(err, "failed to marshal memo payload")
		}
		appendValue("payload", string(payload))
	}
	if update.ClearSpace {
		set = append(set, "space_id = NULL")
	} else if v := update.SpaceID; v != nil {
		appendValue("space_id", *v)
	}
	if len(set) == 0 {
		return nil
	}
	args = append(args, update.ID)
	if _, err := executor.ExecContext(ctx, "UPDATE memo SET "+strings.Join(set, ", ")+" WHERE id = "+placeholder(len(args)), args...); err != nil {
		return errors.Wrap(err, "failed to update memo")
	}
	return nil
}