#!/usr/bin/env julia
using ArgParse

# Scenarios:
# 1. Project is specified, but no files => watch project + run `runtests.jl`.
# 2. Project is specified, and files => watch project + run files.

# Command line arguments.
s = ArgParseSettings()
@add_arg_table s begin
    "files"
    help = "files to both watch and run upon changes"
    nargs = '*'
    action = :store_arg
    "--project"
    help = "path to project"
    "--setup"
    help = "setup script to run before running tests"
    "--test"
    help = "run the `runtests.jl` file in the project upon changes"
    action = :store_true
    "--use-testenv"
    help = "make use of `TestEnv.activate()`"
    action = :store_true
    "--not-all"
    help = "only run upon changes to the target module"
    action = :store_true
    "--show-errors"
    help = "show errors if encountered"
    action = :store_true
    "--verbose"
    help = "show verbose output"
    action = :store_true
end

# Parse command line arguments
parsed_args = parse_args(ARGS, s)

files = parsed_args["files"]
project = parsed_args["project"]
setup = parsed_args["setup"]
istest = parsed_args["test"]
notall = parsed_args["not-all"]
usetestenv = parsed_args["use-testenv"]
verbose = parsed_args["verbose"]

if isempty(files) && !isnothing(project)
    @warn "Project specified, but no files; running as if `--test` was specified."
    istest = true
end

# Activate the module at path.
using Pkg
if !isnothing(project)
    Pkg.activate(project)
end

# Load `Revise`.
using Revise

function revise_watch_and_run(files_to_run, args...; show_errors=false, verbose=false, kwargs...)
    # Revise might encounter an error on the files it's watching, in which case
    # we need to re-trigger `Revise.entr`. BUT to avoid this happening repeatedly,
    # we set `postpone=true` in the `Revise.entr` call above. This postpones the first
    # trigger of the provided `f` until an actual change (which should hopefully be fixing
    # the error that caused Revise to fail).
    revise_errored = false
    while true
        try
            Revise.entr(args...; postpone=revise_errored, kwargs...) do
                try
                    verbose && @info "Detected change; running!"
                    for f in files_to_run
                        verbose && @info "Including" abspath(f)
                        include(abspath(f))
                    end
                catch e
                    if show_errors
                        showerror(stderr, e, catch_backtrace())
                    end
                end

                # Reset `revise_errored`
                revise_errored = false
            end
        catch e
            showerror(stderr, e, catch_backtrace())
            # Set `revise_errored` to true, so that the next time `Revise.entr` is called,
            # we have `postpone=true` and don't trigger revision until a change is detected.
            revise_errored = true
        end
    end
end

files_to_watch = []
files_to_run = []
modules_to_watch = []
mod_sym = nothing

# Activate the test environment for the package.
if usetestenv
    @assert !isnothing(project) "Must specify a project to use `TestEnv`."
    @info "Activating test environment."
    using TestEnv
    # NOTE: Have to get this before `TestEnv.activate`.
    mod_sym = Symbol(TestEnv.current_pkg_name())
    TestEnv.activate()
end

if istest
    @assert !isnothing(project) "Project must be specified if `--test` is specified."
    @info "Loading module in $(project)"

    # Get the current package name.
    if isnothing(mod_sym)
        using TestEnv
        mod_sym = Symbol(TestEnv.current_pkg_name())
    end

    # Load the module and assign it to `mod` so we can reference it.
    @eval begin
        using $mod_sym
        mod = $mod_sym
    end

    # Obtain the path for the `runtests.jl` file.
    testpath = joinpath(dirname(pathof(mod)), "..", "test", "runtests.jl")

    # Watch the module and run the tests.
    push!(files_to_watch, testpath)
    push!(files_to_run, testpath)
    push!(modules_to_watch, mod)
end

if !isempty(files)
    # Watch both module and the specified files, and run the specified files upon changes.
    append!(files_to_watch, files)
    append!(files_to_run, files)
end

# Watch and run!
isempty(files_to_run) && error("Either `--test` or `files` must be specified.")

# Run the setup script if specified.
if !isnothing(setup)
    @info "Including setup script ($setup); to NOT watch modules imported in this too, make sure `--not-all` is specified."
    include(abspath(setup))
end

if isempty(modules_to_watch)
    revise_watch_and_run(
        files_to_run, files_to_watch;
        show_errors=parsed_args["show-errors"],
        verbose=verbose,
        all=!notall,
    )
else
    revise_watch_and_run(
        files_to_run, files_to_watch, modules_to_watch;
        show_errors=parsed_args["show-errors"],
        verbose=verbose,
        all=!notall,
    )
end