35 lines
1.0 KiB
Go
35 lines
1.0 KiB
Go
package store
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import (
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"context"
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"database/sql"
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"fmt"
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)
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// Vote toggles or sets a user's vote on a question (value must be 1 or -1).
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func Vote(ctx context.Context, db *sql.DB, userID, questionID string, value int) error {
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if value != 1 && value != -1 {
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return fmt.Errorf("invalid vote")
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}
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tx, err := db.BeginTx(ctx, nil)
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if err != nil {
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return err
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}
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defer tx.Rollback()
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var current sql.NullInt64
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err = tx.QueryRowContext(ctx, `SELECT value FROM votes WHERE user_id = $1 AND question_id = $2`, userID, questionID).Scan(¤t)
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if err != nil && err != sql.ErrNoRows {
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return err
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}
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if err == nil && current.Valid && int(current.Int64) == value {
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_, err = tx.ExecContext(ctx, `DELETE FROM votes WHERE user_id = $1 AND question_id = $2`, userID, questionID)
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} else {
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_, err = tx.ExecContext(ctx, `INSERT INTO votes (user_id, question_id, value) VALUES ($1, $2, $3)
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ON CONFLICT (user_id, question_id) DO UPDATE SET value = excluded.value`, userID, questionID, value)
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}
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if err != nil {
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return err
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}
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return tx.Commit()
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}
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