local M = {}

-- Function to determine fold level for each line
local function fold_completed_tasks(lnum)
    local line = vim.fn.getline(lnum)
    
    -- Check if the line contains a completed task
    if line:match("%- %[X%]") then
        return ">1" -- Start a fold at level 1
    end
    
    return "0" -- No fold
end

-- Function to hide completed tasks using foldexpr
function M.hide_completed()
    local count = 0
    local pattern = "%- %[X%]"  -- Pattern to match completed tasks: "- [X]"
    
    -- Get all lines in the current buffer
    local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
    
    -- Count completed tasks
    for _, line in ipairs(lines) do
        if line:match(pattern) then
            count = count + 1
        end
    end
    
    -- If no completed tasks found, notify and return
    if count == 0 then
        vim.notify("No completed tasks found", vim.log.levels.INFO)
        return
    end
    
    -- Save current folding settings
    local old_foldmethod = vim.wo.foldmethod
    local old_foldexpr = vim.wo.foldexpr
    
    -- Set up folding based on expression
    vim.wo.foldmethod = "expr"
    vim.wo.foldexpr = "v:lua.require'markdown_organizer'.fold_expr(v:lnum)"
    
    -- Close all folds to hide completed tasks
    vim.cmd("normal! zM")
    
    -- Notify user of how many tasks were hidden
    vim.notify("Hidden " .. count .. " completed tasks", vim.log.levels.INFO)
    
    -- Add autocmd to restore original folding settings when leaving buffer
    vim.api.nvim_create_autocmd("BufLeave", {
        buffer = 0,
        callback = function()
            vim.wo.foldmethod = old_foldmethod
            vim.wo.foldexpr = old_foldexpr
        end,
        once = true
    })
end

-- Expose the fold expression function to be used by foldexpr
function M.fold_expr(lnum)
    return fold_completed_tasks(lnum)
end

-- Function to restore normal folding
function M.show_completed()
    -- Reset folding settings to default
    vim.wo.foldmethod = "manual"
    vim.wo.foldexpr = "0"
    
    -- Open all folds
    vim.cmd("normal! zR")
    
    vim.notify("Showing all tasks", vim.log.levels.INFO)
end

-- Register the commands
vim.api.nvim_create_user_command("HideCompleted", function()
    M.hide_completed()
end, {})

vim.api.nvim_create_user_command("ShowCompleted", function()
    M.show_completed()
end, {})

return M