if vim.g.loaded_cp then
    return
end
vim.g.loaded_cp = 1

local constants = require('cp.constants')
local platforms = constants.PLATFORMS
local actions = constants.ACTIONS

vim.api.nvim_create_user_command('CP', function(opts)
    local cp = require('cp')
    cp.handle_command(opts)
end, {
    nargs = '*',
    desc = 'Competitive programming helper',
    complete = function(ArgLead, CmdLine, _)
        local languages = vim.tbl_keys(constants.canonical_filetypes)

        if ArgLead:match('^--lang=') then
            local lang_completions = {}
            for _, lang in ipairs(languages) do
                table.insert(lang_completions, '--lang=' .. lang)
            end
            return vim.tbl_filter(function(completion)
                return completion:find(ArgLead, 1, true) == 1
            end, lang_completions)
        end

        if ArgLead:match('^%-') and not ArgLead:match('^--lang') then
            return vim.tbl_filter(function(completion)
                return completion:find(ArgLead, 1, true) == 1
            end, { '--lang' })
        end

        local args = vim.split(vim.trim(CmdLine), '%s+')
        local num_args = #args
        if CmdLine:sub(-1) == ' ' then
            num_args = num_args + 1
        end

        local lang_flag_present = vim.tbl_contains(args, '--lang')
            or vim.iter(args):any(function(arg)
                return arg:match('^--lang=')
            end)

        if num_args == 2 then
            local candidates = { '--lang' }
            vim.list_extend(candidates, actions)
            local cp = require('cp')
            local context = cp.get_current_context()
            if context.platform and context.contest_id then
                local cache = require('cp.cache')
                cache.load()
                local contest_data =
                    cache.get_contest_data(context.platform, context.contest_id)
                if contest_data and contest_data.problems then
                    for _, problem in ipairs(contest_data.problems) do
                        table.insert(candidates, problem.id)
                    end
                end
            else
                vim.list_extend(candidates, platforms)
            end
            return vim.tbl_filter(function(cmd)
                return cmd:find(ArgLead, 1, true) == 1
            end, candidates)
        elseif args[#args - 1] == '--lang' then
            return vim.tbl_filter(function(lang)
                return lang:find(ArgLead, 1, true) == 1
            end, languages)
        elseif num_args == 4 and not lang_flag_present then
            if vim.tbl_contains(platforms, args[2]) then
                local cache = require('cp.cache')
                cache.load()
                local contest_data = cache.get_contest_data(args[2], args[3])
                if contest_data and contest_data.problems then
                    local candidates = { '--lang' }
                    for _, problem in ipairs(contest_data.problems) do
                        table.insert(candidates, problem.id)
                    end
                    return vim.tbl_filter(function(cmd)
                        return cmd:find(ArgLead, 1, true) == 1
                    end, candidates)
                end
            end
        end
        return {}
    end,
})