-- Create measures_values table.
-- This table represent a collection of different measured values, because it
-- can be possible, that a sensor returns multiple measured values. For example
-- the BME280 semsor returns humidity, pressure and temperature values.
CREATE TABLE measured_values (
  id                      CHAR(36)                                                NOT NULL,
  sensor_id               CHAR(36)                                                NOT NULL,
  creation_date           TIMESTAMP WITH TIME ZONE    DEFAULT CURRENT_TIMESTAMP   NOT NULL,
  update_date             TIMESTAMP WITH TIME ZONE,
  CONSTRAINT pk_measured_value PRIMARY KEY(id),
  CONSTRAINT pk_measured_value_sensor_id FOREIGN KEY(sensor_id) REFERENCES sensors(sensor_id) ON DELETE CASCADE ON UPDATE CASCADE
);

-- Remove constraints to table sensor
ALTER TABLE humidities
DROP CONSTRAINT fk_humidites_sensor_id;

ALTER TABLE pressures
DROP CONSTRAINT fk_pressures_sensor_id;

ALTER TABLE temperatures
DROP CONSTRAINT fk_temperatures_sensor_id;

-- Rename sensor_id to measured_value_id
ALTER TABLE humidities
RENAME COLUMN sensor_id TO measured_value_id;

ALTER TABLE pressures
RENAME COLUMN sensor_id TO measured_value_id;

ALTER TABLE temperatures
RENAME COLUMN sensor_id TO measured_value_id;

-- Add new column sensor_id with data from measures_value_id
ALTER TABLE humidities
ADD COLUMN sensor_id CHAR(36);

UPDATE humidities
SET sensor_id=measured_value_id;

ALTER TABLE pressures
ADD COLUMN sensor_id CHAR(36);

UPDATE pressures
SET sensor_id=measured_value_id;

ALTER TABLE temperatures
ADD COLUMN sensor_id CHAR(36);

UPDATE temperatures
SET sensor_id=measured_value_id;


DO $$
DECLARE
  f record;
BEGIN
  FOR f IN (
    SELECT
      md5(random()::text || clock_timestamp()::text)::uuid AS measured_value_id,
      h.id AS humidity_id,
      p.id AS pressure_id,
      t.id AS temperature_id,
      CASE WHEN h.sensor_id IS NOT NULL THEN h.sensor_id
           WHEN p.sensor_id IS NOT NULL THEN p.sensor_id
           WHEN t.sensor_id IS NOT NULL THEN t.sensor_id
           ELSE NULL
      END sensor_id
    FROM pressures p
      FULL OUTER JOIN temperatures t ON (t.date = p.date AND t.sensor_id = p.sensor_id)
      FULL OUTER JOIN humidities h ON (h.date = p.date AND h.sensor_id = p.sensor_id)
  ) LOOP

    -- MEASURED_VALUE
    INSERT INTO measured_values(id, sensor_id, creation_date, update_date)
    VALUES (f.measured_value_id, f.sensor_id, NOW(), NULL)
    ON CONFLICT (
      id
    )
    DO NOTHING;

    -- HUMIDITY
    UPDATE humidities
    SET measured_value_id=f.measured_value_id
    WHERE id=f.humidity_id;

    -- PRESSURE
    UPDATE pressures
    SET measured_value_id=f.measured_value_id
    WHERE id=f.pressure_id;

    -- TEMPERATURES
    UPDATE temperatures
    SET measured_value_id=f.measured_value_id
    WHERE id=f.temperature_id;
  END LOOP;
END;
$$;

-- Delete sensor_id columns
ALTER TABLE humidities
DROP COLUMN sensor_id;

ALTER TABLE pressures
DROP COLUMN sensor_id;

ALTER TABLE temperatures
DROP COLUMN sensor_id;

-- Add foreign keys
ALTER TABLE humidities
ADD CONSTRAINT fk_humidites_measured_value_id
FOREIGN KEY (measured_value_id)
REFERENCES measured_values(id)
ON DELETE CASCADE
ON UPDATE CASCADE;

ALTER TABLE pressures
ADD CONSTRAINT fk_pressures_measured_value_id
FOREIGN KEY (measured_value_id)
REFERENCES measured_values(id)
ON DELETE CASCADE
ON UPDATE CASCADE;

ALTER TABLE temperatures
ADD CONSTRAINT fk_temperatures_measured_value_id
FOREIGN KEY (measured_value_id)
REFERENCES measured_values(id)
ON DELETE CASCADE
ON UPDATE CASCADE;