---------------------------
---== TYPES ==-------------

CREATE TYPE doki8902.user_access_type AS ENUM (
    'normal', 'elevated'
);

CREATE TYPE doki8902.user_action_type AS ENUM (
    'post_create',      'post_edit',    'post_delete',
    'comment_create',   'comment_edit', 'comment_delete',
    'user_join', 'user_restrict'
);

---------------------------
---== TABLES ==------------

CREATE TABLE IF NOT EXISTS doki8902.user (
    id          SERIAL
                NOT NULL
                PRIMARY KEY,
    username    VARCHAR(32)
                NOT NULL,
    password    VARCHAR(200)
                NOT NULL,
    join_time   TIMESTAMP WITH TIME ZONE
                NOT NULL
                DEFAULT CURRENT_TIMESTAMP,
    about       VARCHAR(256)
                NOT NULL
                DEFAULT 'Hey! I''m new here!',
    access      doki8902.user_access_type
                NOT NULL
                DEFAULT 'normal',

    CONSTRAINT username_valid_symbols CHECK (username ~ '^[a-zA-Z0-9]*$'),
    CONSTRAINT username_length_min CHECK (char_length(username) >= 3)
);

CREATE TABLE IF NOT EXISTS doki8902.user_session (
    user_id     INT
                NOT NULL
                REFERENCES doki8902.user(id)
                ON UPDATE CASCADE
                ON DELETE CASCADE,
    token       CHAR(32)
                NOT NULL
                PRIMARY KEY
                DEFAULT md5(random()::text),
    expiry      TIMESTAMP
                NOT NULL
                DEFAULT CURRENT_TIMESTAMP + INTERVAL '1 WEEK'
);

CREATE TABLE IF NOT EXISTS doki8902.user_action_log (
    id          SERIAL
                NOT NULL
                PRIMARY KEY,
    user_id     INT
                REFERENCES doki8902.user(id)
                ON DELETE CASCADE
                ON UPDATE CASCADE,
    type        doki8902.user_action_type
                NOT NULL,
    details     VARCHAR(100),
    timestamp   TIMESTAMP WITH TIME ZONE
                NOT NULL
                DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS doki8902.message (
    id              SERIAL
                    NOT NULL
                    PRIMARY KEY,
    author_id       INT
                    REFERENCES doki8902.user(id)
                    ON DELETE SET NULL
                    ON UPDATE CASCADE,
    created_date    TIMESTAMP WITH TIME ZONE
                    NOT NULL
                    DEFAULT CURRENT_TIMESTAMP,
    soft_delete     BOOLEAN
                    NOT NULL
                    DEFAULT FALSE
);
    
CREATE TABLE IF NOT EXISTS doki8902.message_vote (
    message_id  INT
                NOT NULL
                REFERENCES doki8902.message(id)
                ON UPDATE CASCADE
                ON DELETE CASCADE,
    user_id     INT
                NOT NULL
                REFERENCES doki8902.user(id)
                ON UPDATE CASCADE
                ON DELETE CASCADE,
    vote        SMALLINT
                NOT NULL,
    
    CONSTRAINT message_user_id_pkey PRIMARY KEY (message_id, user_id),
    CONSTRAINT vote_value CHECK (vote = 1 OR vote = -1)
);

CREATE TABLE IF NOT EXISTS doki8902.message_content (
    id              SERIAL
                    NOT NULL
                    PRIMARY KEY,
    message_id      INT
                    NOT NULL
                    REFERENCES doki8902.message(id)
                    ON DELETE CASCADE
                    ON UPDATE CASCADE,
    compose_date    TIMESTAMP WITH TIME ZONE
                    NOT NULL
                    DEFAULT CURRENT_TIMESTAMP,
    content         VARCHAR(4096)
                    NOT NULL,
    approved        BOOLEAN
                    NOT NULL
                    DEFAULT FALSE,

    CONSTRAINT content_min_length CHECK (LENGTH(content) >= 2)
);

CREATE TABLE IF NOT EXISTS doki8902.message_initial (
    message_id      INT
                    NOT NULL
                    PRIMARY KEY
                    REFERENCES doki8902.message(id)
                    ON DELETE CASCADE
                    ON UPDATE CASCADE,
    content_id      INT
                    NOT NULL
                    REFERENCES doki8902.message_content(id)
                    ON DELETE CASCADE
                    ON UPDATE CASCADE
);

CREATE TABLE IF NOT EXISTS doki8902.post_category (
    id      SERIAL
            NOT NULL
            PRIMARY KEY,
    name    VARCHAR(100)
            NOT NULL,

    CONSTRAINT name_min_length CHECK (LENGTH(name) >= 2)
);

CREATE TABLE IF NOT EXISTS doki8902.post (
    message_id      INT
                    NOT NULL
                    PRIMARY KEY
                    REFERENCES doki8902.message(id)
                    ON DELETE CASCADE
                    ON UPDATE CASCADE,
    name            VARCHAR(255)
                    NOT NULL,
    category_id     INT
                    NOT NULL
                    REFERENCES doki8902.post_category(id)
                    ON DELETE RESTRICT
                    ON UPDATE CASCADE,

    CONSTRAINT name_min_length CHECK (LENGTH(name) >= 2)
);

CREATE TABLE IF NOT EXISTS doki8902.comment (
    message_id          INT
                        NOT NULL
                        PRIMARY KEY
                        REFERENCES doki8902.message(id),
    parent_comment_id   INT
                        REFERENCES doki8902.comment(message_id)
                        ON DELETE SET NULL
                        ON UPDATE CASCADE,
    post_id             INT
                        NOT NULL
                        REFERENCES doki8902.post(message_id)
                        ON DELETE CASCADE
                        ON UPDATE CASCADE
);

---------------------------
---== VIEWS ==-------------

CREATE OR REPLACE VIEW doki8902.message_votes AS (
    SELECT
        v.message_id,
        SUM(CASE WHEN vote > 0 THEN 1 ELSE 0 END) AS "likes",
        SUM(CASE WHEN vote < 0 THEN 1 ELSE 0 END) AS "dislikes",
        SUM(vote) AS "score"
    FROM
        doki8902.message_vote v
    GROUP BY v.message_id
);

CREATE MATERIALIZED VIEW IF NOT EXISTS doki8902.message_content_latest AS (
    WITH "content_edits" AS (
        SELECT
            m.message_id,
            MAX(m.id) AS "latest_id",
            COUNT(*) AS "edit_count"
        FROM
            doki8902.message_content m
        WHERE
            m.approved
        GROUP BY m.message_id
    )
    SELECT
        e.*,
		CASE
			WHEN e.edit_count = 1 THEN TRUE
			ELSE FALSE
		END AS "original",
        i.content AS "latest_content",
        i.compose_date AS "latest_content_date"
    FROM
        doki8902.message_content i
    JOIN
        content_edits e
            ON e.message_id = i.message_id
    WHERE
        i.id = e.latest_id
);

CREATE OR REPLACE VIEW doki8902.post_comment_metrics AS (
    SELECT
        post_id,
        COUNT(c.*) AS "comment_count",
        COUNT(DISTINCT m.author_id) AS "user_count",
        MAX(m.created_date) AS "latest_activity",
        SUM(v.likes) AS "likes",
        SUM(v.dislikes) AS "dislikes",
        SUM(v.score) AS "score",
        EXTRACT(DAY FROM AGE(MAX(m.created_date))) AS "age"
    FROM
        doki8902.comment c
    JOIN
        doki8902.message AS m
            ON m.id = c.message_id
    JOIN
        doki8902.message_votes AS v
            ON v.message_id = c.message_id
    GROUP BY c.post_id
);

CREATE OR REPLACE VIEW doki8902.message_post AS (
    WITH "post_metrics" AS (
        SELECT
            m.id,
            m.author_id,
            m.created_date,
            m.soft_delete,
            p.name,
            p.category_id,
            v.likes,
            v.dislikes,
            v.score,
            COALESCE(s.comment_count, 0) AS "comment_count",
            COALESCE(s.user_count, 0) AS "user_count",
            COALESCE(s.latest_activity, m.created_date) AS "latest_activity",
            COALESCE(s.likes, 0) + COALESCE(s.dislikes, 0) + v.likes + v.dislikes + COALESCE(s.comment_count, 0) + COALESCE(s.user_count, 0) AS "engagement",
            COALESCE(s.age, EXTRACT(DAY FROM AGE(m.created_date))) AS "age"
        FROM
            doki8902.post p
        JOIN
            doki8902.message AS m
                ON p.message_id = m.id
        JOIN
            doki8902.message_votes AS v
                ON v.message_id = m.id
        LEFT OUTER JOIN
            doki8902.post_comment_metrics AS s
                ON s.post_id = p.message_id
    )
    SELECT
        p.*,
        (p.engagement + p.user_count + p.comment_count) / (p.age + 1) AS "relevancy",
        l.edit_count,
        l.original,
        CASE
            WHEN l.original IS NOT NULL THEN True
            ELSE False
        END AS "reviewed",
        COALESCE(l.latest_content, (
            SELECT c1.content
            FROM doki8902.message_initial i1
            JOIN doki8902.message_content c1 ON c1.id = i1.content_id
			WHERE i1.message_id = p.id
        )) AS "latest_content",
        l.latest_content_date
    FROM
        post_metrics p
    LEFT OUTER JOIN
        doki8902.message_content_latest AS l
            ON l.message_id = p.id
    LEFT OUTER JOIN
        doki8902.post_comment_metrics AS s
            ON s.post_id = p.id
);

CREATE OR REPLACE VIEW doki8902.message_comment AS (
    SELECT
        m.*,
        c.post_id,
        c.parent_comment_id,
        l.edit_count,
        l.original,
        l.latest_content_date,
        v.likes,
        v.dislikes,
        v.score,
        CASE
            WHEN l.original IS NOT NULL THEN True
            ELSE False
        END AS "reviewed",
        COALESCE(l.latest_content, (
            SELECT c1.content
            FROM doki8902.message_initial i1
            JOIN doki8902.message_content c1 ON c1.id = i1.content_id
			WHERE i1.message_id = m.id
        )) AS "latest_content"
    FROM
        doki8902.message m
    JOIN
        doki8902.comment c
            ON c.message_id = m.id
    LEFT OUTER JOIN
        doki8902.message_content_latest l
            ON l.message_id = m.id
    JOIN
        doki8902.message_votes v
            ON v.message_id = m.id
);

---------------------------
---== INDICES ==-----------

CREATE UNIQUE INDEX idx_user_username
    ON doki8902.user(username);

CREATE INDEX IF NOT EXISTS idx_user
    ON doki8902.user_session
    USING HASH (user_id);

CREATE INDEX IF NOT EXISTS idx_message_author
    ON doki8902.message 
    USING HASH (author_id);

CREATE INDEX IF NOT EXISTS idx_message_content_message
    ON doki8902.message_content(message_id, compose_date);  /* TODO */

CREATE INDEX IF NOT EXISTS idx_message_vote_message
    ON doki8902.message_vote
    USING HASH (message_id);

CREATE INDEX IF NOT EXISTS idx_post_category
    ON doki8902.post
    USING HASH (category_id);

CREATE UNIQUE INDEX idx_post_category_name
    ON doki8902.post_category(name);

CREATE INDEX IF NOT EXISTS idx_comment_post
    ON doki8902.comment
    USING HASH (post_id);

CREATE INDEX IF NOT EXISTS idx_comment_parent
    ON doki8902.comment
    USING HASH (parent_comment_id);

CREATE UNIQUE INDEX idx_message_id
    ON doki8902.message_content_latest(message_id);

---------------------------
---== FUNCTIONS ==---------

CREATE OR REPLACE FUNCTION doki8902.func_log_action(
    user_id INT,
    type doki8902.user_action_type,
    details TEXT
) RETURNS VOID AS $$
BEGIN
    INSERT INTO doki8902.user_action_log (user_id, type, details) VALUES (
        user_id, type, details
    );
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION doki8902.func_log_message_trigger() RETURNS TRIGGER AS $$
BEGIN
    PERFORM doki8902.func_log_action(
        (SELECT author_id FROM doki8902.message WHERE id = NEW.message_id),
        CAST(TG_ARGV[0] AS doki8902.user_action_type),
        CAST(NEW.message_id AS TEXT)
    );
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION doki8902.func_log_user_trigger() RETURNS TRIGGER AS $$
BEGIN
    PERFORM doki8902.func_log_action(
        NEW.id,
        CAST(TG_ARGV[0] AS doki8902.user_action_type),
        TG_ARGV[1]
    );

    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION doki8902.func_log_user_restrict(
    user_id INT,
    reason TEXT
) RETURNS VOID AS $$
BEGIN
    PERFORM doki8902.func_log_action(user_id, 'user_restrict', reason);
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION doki8902.func_update_message_contents_trigger() RETURNS TRIGGER AS $$
BEGIN
    REFRESH MATERIALIZED VIEW CONCURRENTLY doki8902.message_content_latest;

    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION doki8902.func_approve_all_pending_content() RETURNS VOID AS $$
BEGIN
    UPDATE doki8902.message_content
        SET approved = TRUE;
END;
$$ LANGUAGE plpgsql;

---------------------------
---== TRIGGERS ==----------

--- USERS
CREATE TRIGGER message_user_join_log
    AFTER INSERT
    ON doki8902.user
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_log_user_trigger('user_join', '');

---
CREATE OR REPLACE FUNCTION doki8902.func_remove_sessions_password_trigger() RETURNS TRIGGER AS $$
BEGIN
    DELETE FROM doki8902.user_session WHERE user_id = NEW.id;

    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER user_password_change
    AFTER UPDATE OF password
    ON doki8902.user
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_remove_sessions_password_trigger();

--- MESSAGE CONTENT
CREATE TRIGGER message_content_update_refresh
    AFTER UPDATE OF approved
    ON doki8902.message_content
    FOR EACH STATEMENT
    EXECUTE FUNCTION doki8902.func_update_message_contents_trigger();

--- MESSAGES
CREATE OR REPLACE FUNCTION doki8902.func_vote_own_created_message_trigger() RETURNS TRIGGER AS $$
BEGIN
    INSERT INTO doki8902.message_vote (message_id, user_id, vote) VALUES (
        NEW.id, NEW.author_id, 1
    );
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_create_vote_auto
    AFTER INSERT
    ON doki8902.message
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_vote_own_created_message_trigger();

---
CREATE OR REPLACE FUNCTION doki8902.func_log_message_delete_trigger() RETURNS TRIGGER AS $$
BEGIN
    IF OLD.soft_delete = FALSE AND NEW.soft_delete = TRUE THEN
        IF EXISTS(SELECT * FROM doki8902.post WHERE NEW.id = message_id) THEN
            PERFORM doki8902.func_log_action(
                (SELECT author_id FROM doki8902.message WHERE id = NEW.message_id),
                'post_delete',
                CAST(NEW.message_id AS TEXT)
            );
        ELSIF EXISTS(SELECT * FROM doki8902.comment WHERE NEW.id = message_id) THEN
            PERFORM doki8902.func_log_action(
                (SELECT author_id FROM doki8902.message WHERE id = NEW.message_id),
                'comment_delete',
                CAST(NEW.message_id AS TEXT)
            );
        END IF;
    END IF;

    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_delete_log
    AFTER UPDATE
    ON doki8902.message
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_log_message_delete_trigger();

---
CREATE OR REPLACE FUNCTION doki8902.func_require_user_trigger() RETURNS TRIGGER AS $$
BEGIN
    IF NOT(EXISTS(SELECT * FROM doki8902.user WHERE id = NEW.author_id))
    THEN
        RAISE EXCEPTION 'Newly created Message must have a valid user %', NEW.author_id USING CONSTRAINT = 'message_require_user';
    END IF;

    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_require_user
    BEFORE INSERT
    ON doki8902.message
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_require_user_trigger();

--- POSTS
CREATE TRIGGER message_post_create_log
    AFTER INSERT
    ON doki8902.post
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_log_message_trigger('post_create');

---
CREATE OR REPLACE FUNCTION doki8902.func_create_message_post_trigger() RETURNS trigger AS $$
DECLARE
    message_id INTEGER;
    content_id INTEGER;
BEGIN
    INSERT INTO doki8902.message(author_id)
    VALUES (NEW.author_id)
    RETURNING id INTO message_id;

    INSERT INTO doki8902.post(message_id, name, category_id)
    VALUES (message_id, NEW.name, NEW.category_id);

    IF (NEW.reviewed = TRUE) THEN
        INSERT INTO doki8902.message_content(message_id, content, approved)
        VALUES (message_id, NEW.latest_content, TRUE)
        RETURNING id INTO content_id;
    ELSE
        INSERT INTO doki8902.message_content(message_id, content)
        VALUES (message_id, NEW.latest_content)
        RETURNING id INTO content_id;
    END IF;

    INSERT INTO doki8902.message_initial(message_id, content_id)
    VALUES (message_id, content_id);

    NEW.id := message_id;
    
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_post_insert
    INSTEAD OF INSERT
    ON doki8902.message_post
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_create_message_post_trigger();

---
CREATE OR REPLACE FUNCTION doki8902.func_update_message_post_content_trigger() RETURNS TRIGGER AS $$
BEGIN
    IF (OLD.latest_content IS DISTINCT FROM NEW.latest_content) THEN
        INSERT INTO doki8902.message_content(message_id, content) VALUES (NEW.id, NEW.latest_content);
    END IF;

    IF (OLD.category_id IS DISTINCT FROM NEW.category_id) THEN
        UPDATE doki8902.post
        SET category_id = NEW.category_id
        WHERE message_id = NEW.id;
    END IF;

    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_post_update_content
    INSTEAD OF UPDATE
    ON doki8902.message_post
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_update_message_post_content_trigger();

--- COMMENTS
CREATE TRIGGER message_post_comment_log
    AFTER INSERT
    ON doki8902.comment
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_log_message_trigger('comment_create');

---
CREATE OR REPLACE FUNCTION doki8902.func_create_message_comment_trigger() RETURNS TRIGGER AS $$
DECLARE
    message_id INTEGER;
    content_id INTEGER;
BEGIN
IF (NEW.parent_comment_id <> NULL AND NOT(
    EXISTS(
        SELECT
            c.*
        FROM
            doki8902.comment c
        WHERE
            c.post_id = NEW.post_id
            AND c.message_id = NEW.parent_comment_id
    )
)) THEN
    RAISE EXCEPTION 'Parent Comment ID % does NOT exist for the Post %', NEW.parent_comment_id, NEW.post_id;
END IF;

    INSERT INTO doki8902.message(author_id)
    VALUES (NEW.author_id)
    RETURNING id INTO message_id;

    INSERT INTO doki8902.comment(message_id, post_id, parent_comment_id)
    VALUES (message_id, NEW.post_id, NEW.parent_comment_id);

    IF (NEW.reviewed = TRUE) THEN
        INSERT INTO doki8902.message_content(message_id, content, approved)
        VALUES (message_id, NEW.latest_content, TRUE)
        RETURNING id INTO content_id;
    ELSE
        INSERT INTO doki8902.message_content(message_id, content)
        VALUES (message_id, NEW.latest_content)
        RETURNING id INTO content_id;
    END IF;

    INSERT INTO doki8902.message_initial(message_id, content_id)
    VALUES (message_id, content_id);

    NEW.id := message_id;
    
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_comment_insert
    INSTEAD OF INSERT
    ON doki8902.message_comment
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_create_message_comment_trigger();

---
CREATE OR REPLACE FUNCTION doki8902.func_update_message_comment_content_trigger() RETURNS TRIGGER AS $$
BEGIN
    IF (OLD.latest_content IS DISTINCT FROM NEW.latest_content)
    THEN
        INSERT INTO doki8902.message_content(message_id, content) VALUES (NEW.id, NEW.latest_content);
    END IF;

    RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_comment_update_content
    INSTEAD OF UPDATE
    ON doki8902.message_comment
    FOR EACH ROW
    EXECUTE FUNCTION doki8902.func_update_message_comment_content_trigger();