-- Conductor Availability
-- This migration creates the conductor availability table

-- =============================================
-- 1. CONDUCTOR AVAILABILITY TABLE
-- =============================================

CREATE TABLE IF NOT EXISTS public.conductor_availability (
    id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
    user_id UUID NOT NULL REFERENCES public.user_profiles(id) ON DELETE CASCADE,
    available_from TIMESTAMP WITH TIME ZONE NOT NULL,
    available_to TIMESTAMP WITH TIME ZONE NOT NULL,
    notes TEXT, -- Optional notes about the availability
    status TEXT NOT NULL DEFAULT 'active' CHECK (status IN ('active', 'cancelled')),
    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
    created_by UUID NOT NULL REFERENCES public.user_profiles(id),
    
    -- Ensure available_to is after available_from
    CONSTRAINT valid_time_range CHECK (available_to > available_from),
    
    -- Ensure availability is in the future (can be modified if needed for past records)
    CONSTRAINT future_availability CHECK (available_from >= NOW() - INTERVAL '1 day')
);

-- =============================================
-- 2. INDEXES FOR PERFORMANCE
-- =============================================

CREATE INDEX IF NOT EXISTS idx_conductor_availability_user_id ON public.conductor_availability(user_id);
CREATE INDEX IF NOT EXISTS idx_conductor_availability_available_from ON public.conductor_availability(available_from);
CREATE INDEX IF NOT EXISTS idx_conductor_availability_available_to ON public.conductor_availability(available_to);
CREATE INDEX IF NOT EXISTS idx_conductor_availability_status ON public.conductor_availability(status);
CREATE INDEX IF NOT EXISTS idx_conductor_availability_created_by ON public.conductor_availability(created_by);
CREATE INDEX IF NOT EXISTS idx_conductor_availability_time_range ON public.conductor_availability(available_from, available_to);

-- =============================================
-- 3. FUNCTIONS FOR OVERLAP PREVENTION
-- =============================================

-- Function to check for overlapping availabilities
CREATE OR REPLACE FUNCTION public.check_availability_overlap()
RETURNS TRIGGER AS $$
DECLARE
    overlap_count INTEGER;
BEGIN
    -- Check for overlapping availabilities for the same user
    SELECT COUNT(*) INTO overlap_count
    FROM public.conductor_availability
    WHERE user_id = NEW.user_id
    AND id != COALESCE(NEW.id, '00000000-0000-0000-0000-000000000000'::UUID)
    AND status = 'active'
    AND (
        -- New availability starts during an existing one
        (NEW.available_from >= available_from AND NEW.available_from < available_to) OR
        -- New availability ends during an existing one
        (NEW.available_to > available_from AND NEW.available_to <= available_to) OR
        -- New availability completely contains an existing one
        (NEW.available_from <= available_from AND NEW.available_to >= available_to) OR
        -- Existing availability completely contains the new one
        (available_from <= NEW.available_from AND available_to >= NEW.available_to)
    );

    IF overlap_count > 0 THEN
        RAISE EXCEPTION 'Availability overlaps with existing availability for user %. Please adjust the time range or cancel the conflicting availability.', NEW.user_id;
    END IF;

    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Function to get available conductors for a specific time range
CREATE OR REPLACE FUNCTION public.get_available_conductors(
    start_time TIMESTAMP WITH TIME ZONE,
    end_time TIMESTAMP WITH TIME ZONE
)
RETURNS TABLE (
    user_id UUID,
    email TEXT,
    available_from TIMESTAMP WITH TIME ZONE,
    available_to TIMESTAMP WITH TIME ZONE
) AS $$
BEGIN
    RETURN QUERY
    SELECT 
        ca.user_id,
        up.email,
        ca.available_from,
        ca.available_to
    FROM public.conductor_availability ca
    JOIN public.user_profiles up ON ca.user_id = up.id
    JOIN public.user_roles ur ON up.id = ur.user_id
    JOIN public.roles r ON ur.role_id = r.id
    WHERE ca.status = 'active'
    AND r.name = 'conductor'
    AND ca.available_from <= start_time
    AND ca.available_to >= end_time
    ORDER BY up.email;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;

-- Function to check if a conductor is available for a specific time range
CREATE OR REPLACE FUNCTION public.is_conductor_available(
    conductor_user_id UUID,
    start_time TIMESTAMP WITH TIME ZONE,
    end_time TIMESTAMP WITH TIME ZONE
)
RETURNS BOOLEAN AS $$
DECLARE
    availability_count INTEGER;
BEGIN
    SELECT COUNT(*) INTO availability_count
    FROM public.conductor_availability
    WHERE user_id = conductor_user_id
    AND status = 'active'
    AND available_from <= start_time
    AND available_to >= end_time;

    RETURN availability_count > 0;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;

-- =============================================
-- 4. TRIGGERS
-- =============================================

-- Create trigger for updated_at on conductor_availability
CREATE TRIGGER set_updated_at_conductor_availability
    BEFORE UPDATE ON public.conductor_availability
    FOR EACH ROW
    EXECUTE FUNCTION public.handle_updated_at();

-- Create trigger to prevent overlapping availabilities
CREATE TRIGGER trigger_check_availability_overlap
    BEFORE INSERT OR UPDATE ON public.conductor_availability
    FOR EACH ROW
    EXECUTE FUNCTION public.check_availability_overlap();

-- =============================================
-- 5. GRANT PERMISSIONS
-- =============================================

GRANT ALL ON public.conductor_availability TO authenticated;

-- =============================================
-- 6. ENABLE ROW LEVEL SECURITY
-- =============================================

ALTER TABLE public.conductor_availability ENABLE ROW LEVEL SECURITY;

-- =============================================
-- 7. CREATE RLS POLICIES
-- =============================================

CREATE POLICY "conductor_availability_select_policy" ON public.conductor_availability
    FOR SELECT
    TO authenticated
    USING (
        -- Users can view their own availability, admins can view all
        user_id = auth.uid() OR public.is_admin()
    );

CREATE POLICY "conductor_availability_insert_policy" ON public.conductor_availability
    FOR INSERT
    TO authenticated
    WITH CHECK (
        -- Users can create their own availability, admins can create for anyone
        (user_id = auth.uid() AND created_by = auth.uid()) OR public.is_admin()
    );

CREATE POLICY "conductor_availability_update_policy" ON public.conductor_availability
    FOR UPDATE
    TO authenticated
    USING (
        -- Users can update their own availability, admins can update any
        user_id = auth.uid() OR public.is_admin()
    )
    WITH CHECK (
        -- Users can update their own availability, admins can update any
        user_id = auth.uid() OR public.is_admin()
    );

CREATE POLICY "conductor_availability_delete_policy" ON public.conductor_availability
    FOR DELETE
    TO authenticated
    USING (
        -- Users can delete their own availability, admins can delete any
        user_id = auth.uid() OR public.is_admin()
    );