USE dating_app;

-- Comment replies: nullable parent comment, self-referencing.
SET @column_exists = (
    SELECT COUNT(*) FROM information_schema.COLUMNS
    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'post_comments' AND COLUMN_NAME = 'parent_comment_id'
);
SET @statement = IF(@column_exists = 0,
    'ALTER TABLE post_comments ADD COLUMN parent_comment_id INT NULL AFTER user_id', 'SELECT 1');
PREPARE migration_statement FROM @statement;
EXECUTE migration_statement;
DEALLOCATE PREPARE migration_statement;

SET @index_exists = (
    SELECT COUNT(*) FROM information_schema.STATISTICS
    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'post_comments'
      AND INDEX_NAME = 'ix_post_comments_parent'
);
SET @statement = IF(@index_exists = 0,
    'ALTER TABLE post_comments ADD INDEX ix_post_comments_parent (parent_comment_id)', 'SELECT 1');
PREPARE migration_statement FROM @statement;
EXECUTE migration_statement;
DEALLOCATE PREPARE migration_statement;

SET @fk_exists = (
    SELECT COUNT(*) FROM information_schema.TABLE_CONSTRAINTS
    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'post_comments'
      AND CONSTRAINT_NAME = 'fk_post_comments_parent'
);
SET @statement = IF(@fk_exists = 0,
    'ALTER TABLE post_comments ADD CONSTRAINT fk_post_comments_parent FOREIGN KEY (parent_comment_id) REFERENCES post_comments(id) ON DELETE CASCADE',
    'SELECT 1');
PREPARE migration_statement FROM @statement;
EXECUTE migration_statement;
DEALLOCATE PREPARE migration_statement;

-- Comment likes.
CREATE TABLE IF NOT EXISTS comment_likes (
    id INT AUTO_INCREMENT PRIMARY KEY,
    comment_id INT NOT NULL,
    user_id INT NOT NULL,
    created_at DATETIME NOT NULL,
    CONSTRAINT uq_comment_like UNIQUE (comment_id, user_id),
    CONSTRAINT fk_comment_likes_comment FOREIGN KEY (comment_id) REFERENCES post_comments(id) ON DELETE CASCADE,
    CONSTRAINT fk_comment_likes_user FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
    INDEX ix_comment_likes_comment (comment_id),
    INDEX ix_comment_likes_user (user_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;