local M = { dsp = {} }

local GAPS <const> = { left = 6, top =  6, right = 6, bottom = 6 }
-- TARGET_POS:
-- | 0 | 1 | 2 |
-- | 3 | 4 | 5 |
-- | 6 | 7 | 8 |
local TARGET_POS <const> = 2

local WINDOW_SIZE <const> = { 960, 480 }

local WS_HIDE <const> = 'special:dropdown'
local TAG_NEW <const> = 'dropdownNew'

local windows = {}
local window_pos_cache = {}
local new_id = nil

hl.on('window.open', function (window)
    for _, v in ipairs(window.tags) do
        if v == TAG_NEW .. '*' and new_id then
            windows[new_id] = window
            hl.dispatch(hl.dsp.window.tag { tag = '-' .. TAG_NEW .. '*', window = window })
            new_id = nil
            return
        end
    end
end)

---@param cmd string
---@return string
local function generate_id(cmd)
    local id = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }

    local id_idx = 1
    local id_len = #id
    for i = 1, #cmd do
        local byteVal = string.byte(cmd, i)
        id[id_idx] = id[id_idx] ~ byteVal
        id_idx = id_idx % id_len + 1
    end

    -- human-readable id
    --local CHARS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    --local CHARS_LEN = #CHARS
    --for i = 1, id_len do
    --    local pos = id[i] % CHARS_LEN + 1
    --    id[i] = CHARS:sub(pos, pos)
    --end
    for i = 1, id_len do
        id[i] = string.char(id[i])
    end

    return table.concat(id)
end

---@param absolute boolean
---@return table
local function get_pos(absolute)
    local m = hl.get_active_monitor()
    if not m then return { 0, 0 } end

    local pos = window_pos_cache[m.name]
    if not pos then
        local r = m.reserved
        local dis_pos = absolute and { m.x + r.left, m.y + r.top } or { r.left, r.top }
        local dis_width = (m.transform % 2 == 0 and m.width or m.height) // m.scale - r.left - r.right
        local dis_height = (m.transform % 2 == 0 and m.height or m.width) // m.scale - r.top - r.bottom
        local targetX = TARGET_POS % 3
        local targetY = TARGET_POS // 3
        pos = {
            targetX == 0 and dis_pos[1] + GAPS.left or (
                targetX == 1 and dis_pos[1] + (dis_width - WINDOW_SIZE[1]) // 2 or
                    dis_pos[1] + dis_width - GAPS.right - WINDOW_SIZE[1]
            ),
            targetY == 0 and dis_pos[2] + GAPS.top or (
                targetY == 1 and dis_pos[2] + (dis_height - WINDOW_SIZE[2]) // 2 or
                    dis_pos[2] + dis_height - GAPS.bottom - WINDOW_SIZE[2]
            ),
        }
        window_pos_cache[m.name] = pos
    end
    return pos
end

---@param window HL.Window
local function hide_window(window)
    hl.dispatch(hl.dsp.window.pin { action = 'off', window = window })
    --hl.dispatch(hl.dsp.window.move { x = POSITION_X, y = HIDDEN_X, relative = false, window = window })
    hl.dispatch(hl.dsp.window.move { workspace = WS_HIDE, follow = false, window = window })
end

---@param window HL.Window
local function hide_others_and_show(window)
    for _, w in pairs(windows) do
        if w == window then
            local pos = get_pos(true)
            hl.dispatch(hl.dsp.window.move { workspace = 'm+0', follow = true, window = w })
            hl.dispatch(hl.dsp.window.move { x = pos[1], y = pos[2], relative = false, window = w })
            hl.dispatch(hl.dsp.window.pin { action = 'on', window = w })
        else
            hide_window(w)
        end
    end
end

---@param cmd string
function M.dsp.toggle(cmd)
    assert(cmd)
    return function ()
        if new_id then return end

        local id = generate_id(cmd)
        local window = windows[id]
        if window then
            if hl.get_window(window) then
                if window.pinned and window.monitor == hl.get_active_monitor() then
                    hide_window(window)
                else
                    hide_others_and_show(window)
                end
                return
            else
                windows[id] = nil
            end
        end

        hide_others_and_show(nil)
        new_id = id
        hl.exec_cmd(cmd, {
            float = true,
            size = WINDOW_SIZE,
            move = get_pos(false),
            pin = true,
            tag = TAG_NEW,
            animation = 'slide',
        })
    end
end

return M