local M = {}

local awful = require("awful")
local object = require("gears.object")
local stack = require("stack")
local timer  = require("gears.timer")

local Workspace = {}

local function desk_find_empty_page(desk)
    for i, page in ipairs(desk.pages) do
        if #page:clients() == 0 then
            return i
        end
    end

    return nil
end

function Workspace:_add_desktop(idx, name, nb_pages)
    local desk = object()

    desk.name = name
    desk.idx  = idx

    desk.pages = {}
    desk.indices_free = stack.Stack:new()
    for i = 1, nb_pages do
        desk.pages[i] = awful.tag.add(string.format("%02x%02x", idx, i), { layout = self.layouts[1] })
        desk.indices_free:push(i)
    end

    desk.screen_map = {}

    desk.find_empty_page = desk_find_empty_page

    self.desktops[idx] = desk
    return idx
end

function Workspace:rename_desktop(idx, name)
    local desk = self.desktops[idx]
    desk.name = name
    desk:emit_signal("desktop:name", name)
end

function Workspace:_apply_state()
    local orig_focus = mouse.screen

    for s in screen do
        if self.screen_state[s] then
            awful.tag.viewnone(s)

            local desk = self.screen_state[s].desktop_idx
            local page = self.desktops[desk].pages[self.screen_state[s].page_idx]
            page.screen = s
        end
    end
    for s in screen do
        local state = self.screen_state[s]
        if state then
            local desk_idx = state.desktop_idx
            local desk     = self.desktops[desk_idx]
            local page_idx = state.page_idx
            local page     = desk.pages[page_idx]

            page:view_only()

            desk:emit_signal("page:view", s, page_idx)
        end
    end

    timer.delayed_call(awful.screen.focus, orig_focus)
end

function Workspace:view(screen, desktop_idx, page_idx)
    local desktop = self.desktops[desktop_idx]

    -- the current state of the target screen
    local state_cur = self.screen_state[screen]

    -- the screen on which the new page is currently displayed (if any)
    local screen_other = nil

    if page_idx == nil then
        -- the page is not specified
        if state_cur and state_cur.desktop_idx == desktop_idx then
            -- requested desktop is already displayed on this screen, nothing to do
            return
        end

        -- take the topmost free one
        page_idx = desktop.indices_free:pop()
        if page_idx == nil then
            print("No free pages on desktop")
            return
        end
    else
        -- check if the page is already displayed somewhere
        screen_other = desktop.screen_map[page_idx]
        if screen_other == screen then
            -- the page is already displayed on this screen, nothing to do
            return
        elseif screen_other == nil then
            desktop.indices_free:remove(page_idx)
        end
    end

    if screen_other then
        -- the page we want is already shown on some other screen, so we swap
        -- the contents of the two screens
        self.screen_state[screen] = self.screen_state[screen_other]
        self.screen_state[screen_other] = state_cur

        desktop.screen_map[page_idx] = screen
        self.signals:emit_signal("desktop:view", screen, desktop_idx)
        if state_cur then
            self.desktops[state_cur.desktop_idx].screen_map[state_cur.page_idx] = screen_other
            self.signals:emit_signal("desktop:view", screen_other, state_cur.desktop_idx)
        end
    else
        -- mark previous page as free
        if state_cur then
            local desk = self.desktops[state_cur.desktop_idx]

            desk.screen_map[state_cur.page_idx] = nil
            desk.indices_free:push(state_cur.page_idx)

            desk:emit_signal("page:hide", state_cur.page_idx)
        end

        desktop.screen_map[page_idx] = screen
        self.screen_state[screen] = { page_idx = page_idx, desktop_idx = desktop_idx }
        self.signals:emit_signal("desktop:view", screen, desktop_idx)
    end

    self:_apply_state()
end

function Workspace:view_relative(offset, screen)
    screen = screen or mouse.screen

    local state = self.screen_state[screen]
    if state then
        local desk = state.desktop_idx
        local page = 1 + ((state.page_idx - 1 + offset) % #self.desktops[desk].pages)

        self:view(screen, desk, page)
    end
end

function Workspace:move_client(client, desk, page)
    local dst_page = self.desktops[desk].pages[page]
    local dst_screen = awful.tag.getscreen(dst_page)
    client:move_to_screen(dst_screen)
    awful.client.movetotag(dst_page, client)
end

function Workspace:client_move_relative(client, offset)
    -- FIXME this is wrong, mouse screen is not necessarily
    -- where the client is
    local state  = self.screen_state[mouse.screen]
    if state then
        local desk = state.desktop_idx
        local page = 1 + ((state.page_idx - 1 + offset) % #self.desktops[desk].pages)

        self:move_client(client, desk, page)
    end
end

function Workspace:new(layouts)
    local o = setmetatable({}, self)
    self.__index = self

    o.desktops     = {}
    o.screen_state = {}
    o.layouts      = layouts

    o.signals   = object()

    for i = 1, 12 do
        o:_add_desktop(i, "Desktop " .. i, 10)
    end

    return o
end

M.Workspace = Workspace

return M