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

using JuliaFEM
using JuliaFEM.Preprocess
using JuliaFEM.Testing

function get_model()
    
    mesh = Mesh()
    add_node!(mesh, 1, [0.0, 0.0])
    add_node!(mesh, 2, [1.0, 0.0])
    add_node!(mesh, 3, [1.0, 0.5])
    add_node!(mesh, 4, [0.0, 0.5])
    add_node!(mesh, 5, [0.0, 0.6])
    add_node!(mesh, 6, [1.0, 0.6])
    add_node!(mesh, 7, [1.0, 1.1])
    add_node!(mesh, 8, [0.0, 1.1])
    add_element!(mesh, 1, :Quad4, [1, 2, 3, 4])
    add_element!(mesh, 2, :Quad4, [5, 6, 7, 8])
    add_element!(mesh, 3, :Seg2, [1, 2])
    add_element!(mesh, 4, :Seg2, [7, 8])
    add_element!(mesh, 5, :Seg2, [4, 3])
    add_element!(mesh, 6, :Seg2, [6, 5])
    add_element_to_element_set!(mesh, :LOWER, 1)
    add_element_to_element_set!(mesh, :UPPER, 2)
    add_element_to_element_set!(mesh, :LOWER_BOTTOM, 3)
    add_element_to_element_set!(mesh, :UPPER_TOP, 4)
    add_element_to_element_set!(mesh, :LOWER_TOP, 5)
    add_element_to_element_set!(mesh, :UPPER_BOTTOM, 6)

    upper = Problem(Elasticity, "UPPER", 2)
    upper.properties.formulation = :plane_stress
    upper.elements = create_elements(mesh, "UPPER")
    update!(upper.elements, "youngs modulus", 288.0)
    update!(upper.elements, "poissons ratio", 1/3)

    lower = Problem(Elasticity, "LOWER", 2)
    lower.properties.formulation = :plane_stress
    lower.elements = create_elements(mesh, "LOWER")
    update!(lower.elements, "youngs modulus", 288.0)
    update!(lower.elements, "poissons ratio", 1/3)

    bc_upper = Problem(Dirichlet, "UPPER_TOP", 2, "displacement")
    bc_upper.elements = create_elements(mesh, "UPPER_TOP")
    #update!(bc_upper.elements, "displacement 1", -17/90)
    #update!(bc_upper.elements, "displacement 1", -17/90)
    update!(bc_upper.elements, "displacement 1", -0.2)
    update!(bc_upper.elements, "displacement 2", -0.2)

    bc_lower = Problem(Dirichlet, "LOWER_BOTTOM", 2, "displacement")
    bc_lower.elements = create_elements(mesh, "LOWER_BOTTOM")
    update!(bc_lower.elements, "displacement 1", 0.0)
    update!(bc_lower.elements, "displacement 2", 0.0)

    interface = Problem(Contact, "LOWER_TO_UPPER", 2, "displacement")
    interface.properties.dimension = 1
    interface_slave_elements = create_elements(mesh, "LOWER_TOP")
    interface_master_elements = create_elements(mesh, "UPPER_BOTTOM")
    update!(interface_slave_elements, "master elements", interface_master_elements)
    interface.elements = [interface_master_elements; interface_slave_elements]

    solver = Solver(Nonlinear)
    push!(solver, upper, lower, bc_upper, bc_lower, interface)
    return solver

end

@testset "test simple two element contact" begin
    solver = get_model()
    solver()
    contact = solver["LOWER_TO_UPPER"]
    master = first(contact.elements)
    slave = last(contact.elements)
    u = master("displacement", [0.0], 0.0)
    la = slave("lambda", [0.0], 0.0)
    info("u = $u, la = $la")
    @test isapprox(u, [-0.2, -0.15])
    @test isapprox(la, [0.0, 30.375])
end