BEGIN;

-- =======================
-- SEQUENCE FOR LETTER NUMBER
-- =======================
CREATE SEQUENCE IF NOT EXISTS letters_incoming_seq;

-- =======================
-- LETTERS INCOMING
-- =======================
CREATE TABLE IF NOT EXISTS letters_incoming (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_number TEXT NOT NULL UNIQUE DEFAULT ('IN-' || lpad(nextval('letters_incoming_seq')::text, 8, '0')),
    reference_number TEXT,
    subject TEXT NOT NULL,
    description TEXT,
    priority_id UUID REFERENCES priorities(id) ON DELETE SET NULL,
    sender_institution_id UUID REFERENCES institutions(id) ON DELETE SET NULL,
    received_date DATE NOT NULL,
    due_date DATE,
    status TEXT NOT NULL DEFAULT 'new' CHECK (status IN ('new','in_progress','completed')),
    created_by UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    deleted_at TIMESTAMP WITHOUT TIME ZONE
);

CREATE INDEX IF NOT EXISTS idx_letters_incoming_status ON letters_incoming(status);
CREATE INDEX IF NOT EXISTS idx_letters_incoming_received_date ON letters_incoming(received_date);

CREATE TRIGGER trg_letters_incoming_updated_at
    BEFORE UPDATE ON letters_incoming
    FOR EACH ROW EXECUTE FUNCTION set_updated_at();

-- =======================
-- LETTER INCOMING RECIPIENTS
-- =======================
CREATE TABLE IF NOT EXISTS letter_incoming_recipients (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_id UUID NOT NULL REFERENCES letters_incoming(id) ON DELETE CASCADE,
    recipient_user_id UUID REFERENCES users(id) ON DELETE SET NULL,
    recipient_department_id UUID REFERENCES departments(id) ON DELETE SET NULL,
    status TEXT NOT NULL DEFAULT 'new' CHECK (status IN ('new','read','completed')),
    read_at TIMESTAMP WITHOUT TIME ZONE,
    completed_at TIMESTAMP WITHOUT TIME ZONE,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX IF NOT EXISTS idx_letter_incoming_recipients_letter ON letter_incoming_recipients(letter_id);

-- =======================
-- LETTER INCOMING LABELS (M:N)
-- =======================
CREATE TABLE IF NOT EXISTS letter_incoming_labels (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_id UUID NOT NULL REFERENCES letters_incoming(id) ON DELETE CASCADE,
    label_id UUID NOT NULL REFERENCES labels(id) ON DELETE CASCADE,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    UNIQUE (letter_id, label_id)
);

CREATE INDEX IF NOT EXISTS idx_letter_incoming_labels_letter ON letter_incoming_labels(letter_id);

-- =======================
-- LETTER INCOMING ATTACHMENTS
-- =======================
CREATE TABLE IF NOT EXISTS letter_incoming_attachments (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_id UUID NOT NULL REFERENCES letters_incoming(id) ON DELETE CASCADE,
    file_url TEXT NOT NULL,
    file_name TEXT NOT NULL,
    file_type TEXT NOT NULL,
    uploaded_by UUID REFERENCES users(id) ON DELETE SET NULL,
    uploaded_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX IF NOT EXISTS idx_letter_incoming_attachments_letter ON letter_incoming_attachments(letter_id);

-- =======================
-- LETTER DISPOSITIONS
-- =======================
CREATE TABLE IF NOT EXISTS letter_dispositions (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_id UUID NOT NULL REFERENCES letters_incoming(id) ON DELETE CASCADE,
    from_user_id UUID REFERENCES users(id) ON DELETE SET NULL,
    from_department_id UUID REFERENCES departments(id) ON DELETE SET NULL,
    to_user_id UUID REFERENCES users(id) ON DELETE SET NULL,
    to_department_id UUID REFERENCES departments(id) ON DELETE SET NULL,
    notes TEXT,
    status TEXT NOT NULL DEFAULT 'pending' CHECK (status IN ('pending','read','rejected','completed')),
    created_by UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    read_at TIMESTAMP WITHOUT TIME ZONE,
    completed_at TIMESTAMP WITHOUT TIME ZONE,
    updated_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX IF NOT EXISTS idx_letter_dispositions_letter ON letter_dispositions(letter_id);

CREATE TRIGGER trg_letter_dispositions_updated_at
    BEFORE UPDATE ON letter_dispositions
    FOR EACH ROW EXECUTE FUNCTION set_updated_at();

-- =======================
-- DISPOSITION NOTES
-- =======================
CREATE TABLE IF NOT EXISTS disposition_notes (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    disposition_id UUID NOT NULL REFERENCES letter_dispositions(id) ON DELETE CASCADE,
    user_id UUID REFERENCES users(id) ON DELETE SET NULL,
    note TEXT NOT NULL,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX IF NOT EXISTS idx_disposition_notes_disposition ON disposition_notes(disposition_id);

-- =======================
-- LETTER DISPOSITION ACTIONS (Selections)
-- =======================
CREATE TABLE IF NOT EXISTS letter_disposition_actions (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    disposition_id UUID NOT NULL REFERENCES letter_dispositions(id) ON DELETE CASCADE,
    action_id UUID NOT NULL REFERENCES disposition_actions(id) ON DELETE RESTRICT,
    note TEXT,
    created_by UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    UNIQUE (disposition_id, action_id)
);

CREATE INDEX IF NOT EXISTS idx_letter_disposition_actions_disposition ON letter_disposition_actions(disposition_id);

-- =======================
-- LETTER INCOMING DISCUSSIONS (Threaded)
-- =======================
CREATE TABLE IF NOT EXISTS letter_incoming_discussions (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_id UUID NOT NULL REFERENCES letters_incoming(id) ON DELETE CASCADE,
    parent_id UUID REFERENCES letter_incoming_discussions(id) ON DELETE CASCADE,
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
    message TEXT NOT NULL,
    mentions JSONB,
    created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    edited_at TIMESTAMP WITHOUT TIME ZONE
);

CREATE INDEX IF NOT EXISTS idx_letter_incoming_discussions_letter ON letter_incoming_discussions(letter_id);
CREATE INDEX IF NOT EXISTS idx_letter_incoming_discussions_parent ON letter_incoming_discussions(parent_id);

CREATE TRIGGER trg_letter_incoming_discussions_updated_at
    BEFORE UPDATE ON letter_incoming_discussions
    FOR EACH ROW EXECUTE FUNCTION set_updated_at();

-- =======================
-- LETTER INCOMING DISCUSSION ATTACHMENTS
-- =======================
CREATE TABLE IF NOT EXISTS letter_incoming_discussion_attachments (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    discussion_id UUID NOT NULL REFERENCES letter_incoming_discussions(id) ON DELETE CASCADE,
    file_url TEXT NOT NULL,
    file_name TEXT NOT NULL,
    file_type TEXT NOT NULL,
    uploaded_by UUID REFERENCES users(id) ON DELETE SET NULL,
    uploaded_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX IF NOT EXISTS idx_letter_incoming_discussion_attachments_discussion ON letter_incoming_discussion_attachments(discussion_id);

-- =======================
-- LETTER INCOMING ACTIVITY LOGS (Immutable)
-- =======================
CREATE TABLE IF NOT EXISTS letter_incoming_activity_logs (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    letter_id UUID NOT NULL REFERENCES letters_incoming(id) ON DELETE CASCADE,
    action_type TEXT NOT NULL,
    actor_user_id UUID REFERENCES users(id) ON DELETE SET NULL,
    actor_department_id UUID REFERENCES departments(id) ON DELETE SET NULL,
    target_type TEXT,
    target_id UUID,
    from_status TEXT,
    to_status TEXT,
    context JSONB,
    occurred_at TIMESTAMP WITHOUT TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX IF NOT EXISTS idx_letter_incoming_activity_logs_letter ON letter_incoming_activity_logs(letter_id);
CREATE INDEX IF NOT EXISTS idx_letter_incoming_activity_logs_action ON letter_incoming_activity_logs(action_type);

COMMIT;