import json
from enum import Enum
from utils.value import AttributeChange

# Specific heat capacities [J/(kg*K)] used to derive a single lumped
# (mass, specific heat) pair for the pot's contents from pot_mass/
# grain_mass/water_mass. Approximate, typical values.
SPECIFIC_HEAT_WATER = 4190
SPECIFIC_HEAT_GRAIN = 1800
SPECIFIC_HEAT_BY_MATERIAL = {
	"Edelstahl 18/10": 500,
}


class SudState(Enum):
	IDLE = 0
	RAMPING = 1
	HOLDING = 2
	WAIT_USER = 3
	DONE = 4


class Sud(AttributeChange):
	def __init__(self, path):
		AttributeChange.__init__(self)
		with open(path) as f:
			data = json.load(f)

		self.name = data.get('Name', '')
		self.description = data.get('Description', '')
		self.schedule = data['schedule']

		self.pot_mass = data.get('pot_mass', 0)
		self.pot_material = data.get('pot_material')
		self.grain_mass = data.get('grain_mass', 0)
		self.water_mass = data.get('water_mass', 0)

		self.index = -1
		self.hold_remaining = 0.0
		self.state = SudState.IDLE
		self.step = None
		self.user_message = None

	def derive_plant_params(self):
		"""Lumped (mass, specific heat) lifted from pot_mass/pot_material/
		grain_mass/water_mass, for use as Pot's "M"/"C" params."""
		c_pot = SPECIFIC_HEAT_BY_MATERIAL.get(self.pot_material, SPECIFIC_HEAT_WATER)
		mass = self.water_mass + self.grain_mass + self.pot_mass
		capacitance = (self.water_mass * SPECIFIC_HEAT_WATER
			+ self.grain_mass * SPECIFIC_HEAT_GRAIN
			+ self.pot_mass * c_pot)

		return {
			'M': mass,
			'C': capacitance / mass if mass > 0 else SPECIFIC_HEAT_WATER,
		}

	def start(self):
		if self.state != SudState.IDLE:
			return
		self.index = -1
		self._advance()

	def confirm(self):
		if self.state == SudState.WAIT_USER:
			self._advance()

	def temp_reached(self):
		if self.state == SudState.RAMPING:
			self._finish_step()

	def tick(self, dt):
		if self.state == SudState.HOLDING:
			self.hold_remaining -= dt
			if self.hold_remaining <= 0:
				self._finish_step()

	def _advance(self):
		self.index += 1
		if self.index >= len(self.schedule):
			self.state = SudState.DONE
			self.user_message = None
			self.step = None
			return

		next_step = self.schedule[self.index]
		if next_step['type'] == 'heat':
			self.state = SudState.RAMPING
		else:
			self.hold_remaining = next_step.get('duration', 0)
			self.state = SudState.HOLDING

		self.user_message = next_step.get('user_message')
		self.step = next_step

	def _finish_step(self):
		if self.step.get('user_wait_for_continue', False):
			self.state = SudState.WAIT_USER
		else:
			self._advance()