local highlight = require("rc.highlight")
local line = require("rc.line")
local ui = require("rc.ui")

---@return string
local function overseer_info()
    local result = ""
    if not package.loaded.overseer then
        return result
    end

    local tasks = require("overseer.task_list").list_tasks({ unique = true })
    local tasks_by_status = require("overseer.util").tbl_group_by(tasks, "status")

    for status, symbol in pairs(ui.status) do
        status = status:upper()
        local task = tasks_by_status[status]
        if task then
            result = result
                .. line.with_hl(
                    symbol .. " " .. #task,
                    highlight.ensure("TabLineOverseer" .. status, function()
                        return highlight.get("Overseer" .. status):extend("TabLineFill")
                    end)
                )
                .. " "
        end
    end

    return result
end

---@param buf integer
---@return boolean
local function is_modified(buf)
    return vim.api.nvim_get_option_value("modified", { buf = buf })
end

---@param buffer integer
---@param is_selected boolean
---@return string
local function buffer_info(buffer, is_selected)
    local bufname = vim.api.nvim_buf_get_name(buffer)
    local hl_suffix = is_selected and "Sel" or ""
    local hl_group = "TabLine" .. hl_suffix
    local t = ""

    local sep_hl = highlight.ensure("TabLineSep", function()
        return highlight.get("TabLineFill"):extend(highlight.get("Normal"):reverse():clear_bg())
    end)

    if is_selected then
        t = t .. line.with_hl("", sep_hl.name)
    end
    t = t .. line.with_hl((is_selected and "  " or " "), hl_group)
    t = t .. line.with_hl(" " .. vim.fs.basename(bufname) .. " ", hl_group)

    if is_modified(buffer) then
        t = t
            .. line.with_hl(
                "" .. (is_selected and "" or " "),
                highlight.ensure("TabLineModified" .. hl_suffix, function()
                    return highlight.get("Function"):extend(hl_group)
                end)
            )
    else
        t = t .. line.with_hl(" ", hl_group)
    end

    t = t .. line.with_hl(is_selected and " " or "", hl_group)
    if is_selected then
        t = t .. line.with_hl("", sep_hl)
    end

    return t
end

---@param buffer integer
local function filter_buffer(buffer)
    return vim.api.nvim_buf_is_loaded(buffer)
        and vim.api.nvim_get_option_value("buflisted", { buf = buffer })
        and vim.api.nvim_buf_get_name(buffer) ~= ""
end

---@return string
local function get_tabline()
    local current_buf = vim.api.nvim_get_current_buf()
    local tabline = vim.iter(vim.api.nvim_list_bufs())
        :filter(filter_buffer)
        :map(function(buf)
            return buffer_info(buf, buf == current_buf)
        end)
        :join("")

    tabline = tabline .. "%=" .. overseer_info()
    return tabline
end

local M = {}

function M.setup()
    vim.o.showtabline = 2
    vim.o.tabline = line.as_opt(get_tabline)
    vim.api.nvim_create_autocmd({ "BufAdd", "BufDelete" }, { command = "redrawtabline" })
end

return M