using Stochy, Stochy.GadflySupport, Gadfly, DataStructures

@pp function rainprior()
    flip(0.3)
end

@pp function sprinklerprior()
    flip(0.2)
end

@pp function wetgrassprior(rain, sprinkler)
    flip(
    !rain && !sprinkler ? 0.05 :
    !rain && sprinkler  ? 0.9  :
    rain  && !sprinkler ? 0.9  :
    rain  && sprinkler  ? 0.95 : :unreachable)
end

@pp function model()
    local
    r = rainprior(),
    s = sprinklerprior(),
    w = wetgrassprior(r,s)
    tuple(r,s,w)
end        

@pp model() # Generate a sample from the model.

joint = @pp enum() do
    model()
end

bar(joint)

prior = @pp enum() do
    local triple = model()
    triple[1] # rain
end

bar(prior)

d1 = @pp enum() do
    local triple = model()
    factor(triple[3] ? 0 : -Inf) # Observe the grass is wet.
    triple[1]
end    

bar(d1)

d2 = @pp enum() do
    local triple = model()
    factor(triple[3] && triple[2] ? 0 : -Inf) # Also observe that the sprinkler is on.
    triple[1]
end

bar(d2)