-- 图片独立表：将原先挤在 chapter.cover_image / chapter_sections.image 的 JSON 拆成独立列
-- 执行顺序: 1) 本文件  2) python -m api.scripts.run_memoir_images_migration
-- 执行方式: psql -U <user> -d <database> -f api/migrations/add_memoir_images_table.sql

-- ========== 1. 新建 memoir_images 表 ==========
CREATE TABLE IF NOT EXISTS memoir_images (
    id VARCHAR NOT NULL PRIMARY KEY,
    chapter_id VARCHAR NOT NULL REFERENCES chapters(id) ON DELETE CASCADE,
    section_id VARCHAR NULL REFERENCES chapter_sections(id) ON DELETE CASCADE,
    order_index INTEGER NOT NULL DEFAULT 0,
    placeholder TEXT,
    description TEXT,
    status VARCHAR NOT NULL DEFAULT 'pending',
    prompt TEXT,
    url TEXT,
    storage_key TEXT,
    provider VARCHAR,
    style VARCHAR,
    size VARCHAR,
    error TEXT,
    retryable BOOLEAN,
    created_at TIMESTAMP WITH TIME ZONE,
    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
);

COMMENT ON TABLE memoir_images IS '章节配图与封面：section_id 为空表示章节封面，非空表示该 section 的配图';
COMMENT ON COLUMN memoir_images.order_index IS '章节内唯一：封面=0，段落配图=1,2,3,...（对应 section.order_index+1）';

CREATE INDEX IF NOT EXISTS ix_memoir_images_chapter_id ON memoir_images(chapter_id);
CREATE INDEX IF NOT EXISTS ix_memoir_images_section_id ON memoir_images(section_id);
CREATE UNIQUE INDEX IF NOT EXISTS ix_memoir_images_chapter_cover ON memoir_images(chapter_id) WHERE section_id IS NULL;
CREATE UNIQUE INDEX IF NOT EXISTS ix_memoir_images_section_unique ON memoir_images(section_id) WHERE section_id IS NOT NULL;