import Plots._current_plots_version

# Taken from MakieGallery
"""
Downloads the reference images from ReferenceImages for a specific version
"""
function download_reference(version = v"0.0.1")
    download_dir = abspath(@__DIR__, "reference_images")
    isdir(download_dir) || mkpath(download_dir)
    tarfile = joinpath(download_dir, "reference_images.zip")
    url = "https://github.com/JuliaPlots/PlotReferenceImages.jl/archive/v$(version).tar.gz"
    refpath = joinpath(download_dir, "PlotReferenceImages.jl-$(version)")
    if !isdir(refpath) # if not yet downloaded
        @info "downloading reference images for version $version"
        download(url, tarfile)
        BinaryProvider.unpack(tarfile, download_dir)
        # check again after download
        if !isdir(refpath)
            error("Something went wrong while downloading reference images. Plots can't be compared to references")
        else
            rm(tarfile, force = true)
        end
    else
        @info "using reference images for version $version (already downloaded)"
    end
    refpath
end

const ref_image_dir = download_reference()

function image_comparison_tests(pkg::Symbol, idx::Int; debug = false, popup = isinteractive(), sigma = [1,1], tol = 1e-2)
    Plots._debugMode.on = debug
    example = Plots._examples[idx]
    Plots.theme(:default)
    @info("Testing plot: $pkg:$idx:$(example.header)")
    backend(pkg)
    backend()
    default(size=(500,300))
    # ensure consistent results
    Random.seed!(1234)

    # reference image directory setup
    refdir = joinpath(ref_image_dir, "Plots", string(pkg))
    fn = "ref$idx.png"

    # firgure out version info
    vns = filter(x->x[1] != '.', readdir(refdir))
    versions = sort(VersionNumber.(vns), rev = true)
    versions = filter(v -> v <= _current_plots_version, versions)
    # @show refdir fn versions

    newdir = joinpath(refdir, string(_current_plots_version))
    newfn = joinpath(newdir, fn)

    # figure out which reference file we should compare to, by finding the highest versioned file
    reffn = nothing
    for v in versions
        tmpfn = joinpath(refdir, string(v), fn)
        if isfile(tmpfn)
            reffn = tmpfn
            break
        end
    end

    # now we have the fn (if any)... do the comparison
    # @show reffn
    if reffn === nothing
        reffn = newfn
    end
    # @show reffn
    # return

    # test function
    func = (fn, idx) -> begin
        expr = Expr(:block)
        append!(expr.args, example.exprs)
        eval(expr)
        png(fn)
    end

    # try
    #     run(`mkdir -p $newdir`)
    # catch err
    #     display(err)
    # end
    # # reffn = joinpath(refdir, "ref$idx.png")

    # the test
    vtest = VisualTest(func, reffn, idx)
    test_images(vtest, popup=popup, sigma=sigma, tol=tol, newfn = newfn)
end

function image_comparison_facts(pkg::Symbol;
                                skip = [],      # skip these examples (int index)
                                only = nothing, # limit to these examples (int index)
                                debug = false,  # print debug information?
                                sigma = [1,1],  # number of pixels to "blur"
                                tol = 1e-2)     # acceptable error (percent)
  for i in 1:length(Plots._examples)
    i in skip && continue
    if only === nothing || i in only
      @test image_comparison_tests(pkg, i, debug=debug, sigma=sigma, tol=tol) |> success == true
    end
  end
end