# This file is a part of JuliaFEM.
# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md

function ForwardDiff.derivative{T}(f::Function, S::Matrix{T}, args...)
    shape = size(S)
    wrapper(S::Vector) = f(reshape(S, shape))
    deriv = ForwardDiff.gradient(wrapper, vec(S), args...)
    return reshape(deriv, shape)
end

"""
Integration point

xi
    (dimensionless) coordinates of integration point
weight
    integration weight
fields
    FieldSet what can be used to store internal variables, stress, strain, ...
"""
immutable IntegrationPoint
    xi :: Vector
    weight :: Float64
    fields :: Dict{ASCIIString, Field}
    changed :: Bool
end

function IntegrationPoint(xi, weight)
    return IntegrationPoint(xi, weight, FieldSet(), false)
end

function setindex!{T<:ForwardDiff.ForwardDiffNumber}(ip::IntegrationPoint, data::Array{T,2}, field_name::ASCIIString)
    data = ForwardDiff.get_value(data)
    setindex!(ip, data, field_name)
end
function setindex!(ip::IntegrationPoint, data, field_name)
    ip.fields[field_name] = Field(data)
    ip.changed = true
end

function getindex(ip::IntegrationPoint, field_name::ASCIIString)
    ip.fields[field_name]
end

function convert(::Type{Number}, ip::IntegrationPoint)
    return ip.xi
end

function call(field::CVTI, ip::IntegrationPoint)
    return call(field, ip.xi)
end

function call(basis::CVTI, field::DCTI, ip::IntegrationPoint)
    call(basis, field, ip.xi)
end

function call(basis::CVTI, field::DVTI, ip::IntegrationPoint, ::Type{Val{:grad}})
    call(basis, field, ip.xi, Val{:grad})
end

function call(basis::CVTI, field::DVTI, ip::IntegrationPoint)
    call(basis, field, ip.xi)
end

function call(basis::CVTI, geometry::DVTI, field::Union{DCTI, DVTI}, ip::IntegrationPoint, ::Type{Val{:grad}})
    call(basis, geometry, field, ip.xi, Val{:grad})
end

#function Base.call(basis::Basis, increment::Increment, ip::IntegrationPoint)
#    return call(basis, increment, ip.xi)
#end
#function Base.call(basis::Basis, increment::Increment, ip::IntegrationPoint, ::Type{Val{:grad}})
#    return call(basis, increment, ip.xi, Val{:grad})
#end
#function Base.call(basis::Basis, field::Field, ip::IntegrationPoint, ::Type{Val{:grad}})
#    return call(basis, field, ip.xi, Val{:grad})
#end
#function Base.call(basis::Basis, geometry::Increment, field::Increment, ip::IntegrationPoint, ::Type{Val{:grad}})
#    return call(basis, geometry, field, ip.xi, Val{:grad})
#end
#function Base.call(basis::Basis, field::Field, ip::IntegrationPoint)
#    return call(basis, field, ip.xi)
#end