-- Migration: Knowledge Base tables with optional pgvector support
-- 5 tables: knowledge_categories, knowledge_items, knowledge_chunks,
--           knowledge_versions, knowledge_usage
--
-- pgvector is optional: if the extension is not installed, the embedding
-- column and HNSW index are skipped. All other tables work normally.

-- 行业分类树
CREATE TABLE IF NOT EXISTS knowledge_categories (
    id TEXT PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    description TEXT,
    parent_id TEXT REFERENCES knowledge_categories(id) ON DELETE RESTRICT,
    icon VARCHAR(50),
    sort_order INT DEFAULT 0,
    created_at TIMESTAMPTZ DEFAULT NOW(),
    updated_at TIMESTAMPTZ DEFAULT NOW(),
    CHECK (id != parent_id)
);
CREATE INDEX IF NOT EXISTS idx_kc_parent ON knowledge_categories(parent_id);

-- 知识条目
CREATE TABLE IF NOT EXISTS knowledge_items (
    id TEXT PRIMARY KEY,
    category_id TEXT NOT NULL REFERENCES knowledge_categories(id) ON DELETE RESTRICT,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    keywords TEXT[] DEFAULT '{}',
    related_questions TEXT[] DEFAULT '{}',
    priority INT DEFAULT 0,
    status VARCHAR(20) DEFAULT 'active' CHECK (status IN ('active', 'archived', 'deprecated', 'draft')),
    version INT DEFAULT 1,
    source VARCHAR(50) DEFAULT 'manual',
    tags TEXT[] DEFAULT '{}',
    created_by TEXT NOT NULL REFERENCES accounts(id),
    created_at TIMESTAMPTZ DEFAULT NOW(),
    updated_at TIMESTAMPTZ DEFAULT NOW(),
    CHECK (length(content) <= 100000)
);
CREATE INDEX IF NOT EXISTS idx_ki_category ON knowledge_items(category_id);
CREATE INDEX IF NOT EXISTS idx_ki_status_updated ON knowledge_items(status, updated_at DESC);
CREATE INDEX IF NOT EXISTS idx_ki_keywords ON knowledge_items USING GIN(keywords);

-- 知识分块（RAG 检索核心）
-- 基础表不含 embedding 列；若 pgvector 可用则后续通过 DO 块添加
CREATE TABLE IF NOT EXISTS knowledge_chunks (
    id TEXT PRIMARY KEY,
    item_id TEXT NOT NULL REFERENCES knowledge_items(id) ON DELETE CASCADE,
    chunk_index INT NOT NULL,
    content TEXT NOT NULL,
    keywords TEXT[] DEFAULT '{}',
    created_at TIMESTAMPTZ DEFAULT NOW()
);
CREATE UNIQUE INDEX IF NOT EXISTS idx_kchunks_item_idx ON knowledge_chunks(item_id, chunk_index);
CREATE INDEX IF NOT EXISTS idx_kchunks_item ON knowledge_chunks(item_id);
CREATE INDEX IF NOT EXISTS idx_kchunks_keywords ON knowledge_chunks USING GIN(keywords);

-- 条件添加 embedding 列和 HNSW 索引（仅当 pgvector 可用时）
DO $$ BEGIN
    PERFORM set_config('client_min_messages', 'warning', true);
    CREATE EXTENSION IF NOT EXISTS vector;
    IF NOT EXISTS (
        SELECT 1 FROM information_schema.columns
        WHERE table_name = 'knowledge_chunks' AND column_name = 'embedding'
    ) THEN
        ALTER TABLE knowledge_chunks ADD COLUMN embedding vector(1536);
    END IF;
    IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_kchunks_embedding') THEN
        CREATE INDEX idx_kchunks_embedding ON knowledge_chunks
            USING hnsw (embedding vector_cosine_ops)
            WITH (m = 16, ef_construction = 128);
    END IF;
    RAISE NOTICE 'pgvector enabled for knowledge base';
EXCEPTION WHEN OTHERS THEN
    RAISE NOTICE 'pgvector not available, vector features disabled: %', SQLERRM;
END $$;

-- 版本快照
CREATE TABLE IF NOT EXISTS knowledge_versions (
    id TEXT PRIMARY KEY,
    item_id TEXT NOT NULL REFERENCES knowledge_items(id) ON DELETE CASCADE,
    version INT NOT NULL,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    keywords TEXT[] DEFAULT '{}',
    related_questions TEXT[] DEFAULT '{}',
    change_summary TEXT,
    created_by TEXT NOT NULL REFERENCES accounts(id),
    created_at TIMESTAMPTZ DEFAULT NOW()
);
CREATE INDEX IF NOT EXISTS idx_kv_item ON knowledge_versions(item_id);

-- 使用追踪
CREATE TABLE IF NOT EXISTS knowledge_usage (
    id TEXT PRIMARY KEY,
    item_id TEXT REFERENCES knowledge_items(id) ON DELETE SET NULL,
    chunk_id TEXT REFERENCES knowledge_chunks(id) ON DELETE SET NULL,
    session_id VARCHAR(100),
    query_text TEXT,
    relevance_score FLOAT,
    was_injected BOOLEAN DEFAULT FALSE,
    agent_feedback VARCHAR(20) CHECK (agent_feedback IN ('positive', 'negative')),
    created_at TIMESTAMPTZ DEFAULT NOW()
);
CREATE INDEX IF NOT EXISTS idx_ku_item ON knowledge_usage(item_id) WHERE item_id IS NOT NULL;
CREATE INDEX IF NOT EXISTS idx_ku_created_brin ON knowledge_usage USING brin(created_at);

-- 权限种子数据（使用 jsonb 操作避免 REPLACE 脆弱性）
UPDATE roles
SET permissions = (
    SELECT '[' || string_agg('"' || elem || '"', ', ') || ']'
    FROM (
        SELECT DISTINCT elem
        FROM json_array_elements_text(permissions::json) AS elem
        UNION ALL SELECT 'knowledge:read'
        UNION ALL SELECT 'knowledge:write'
        UNION ALL SELECT 'knowledge:admin'
        UNION ALL SELECT 'knowledge:search'
    ) sub
)
WHERE id = 'super_admin'
AND permissions NOT LIKE '%knowledge:read%';

UPDATE roles
SET permissions = (
    SELECT '[' || string_agg('"' || elem || '"', ', ') || ']'
    FROM (
        SELECT DISTINCT elem
        FROM json_array_elements_text(permissions::json) AS elem
        UNION ALL SELECT 'knowledge:read'
        UNION ALL SELECT 'knowledge:write'
        UNION ALL SELECT 'knowledge:search'
    ) sub
)
WHERE id = 'admin'
AND permissions NOT LIKE '%knowledge:read%';