feat(tasks): add agenda view

after/ftplugin/markdown.lua

···
     refactor = { pattern = "refactor%:", group = "@comment.info" },
     fix = { pattern = "fix%:", group = "@comment.error" },
     docs = { pattern = "docs%:", group = "@label" },
+    test = { pattern = "test%:", group = "@comment.note" },
   },
 }

lua/core/keymaps.lua

···
 -- notes
 u.map("n", "<leader>ot", "<cmd>e $HOME/org/todo.txt<cr>") --codespell:ignore
 u.map("n", "<leader>oi", "<cmd>e $HOME/org/notes/Inbox/Inbox.md<cr>")
+u.map("n", "<leader>a", require("scratch.tasks").agenda)
 
 -- general
 u.map("n", "<leader>q", "<cmd>quit!<cr>")

lua/scratch/tasks.lua

···
+---@param name string
+---@return string
+local function task_file(name)
+  return vim.fs.joinpath(vim.fn.expand "~/org/notes", name .. ".md")
+end
+
 local config = {
   label = "done:%Y%m%d-%H%M",
   archive_header = "# Archive",
+  task_files = {
+    task_file "TODO",
+    task_file "Onasty",
+    task_file "GBAC",
+    task_file "Projects/gopher.nvim",
+  },
 }
 
--- TODO: highlight the `feat:`, `docs:`, `fix:`, probably should be done with `mini.hipatterns`
 -- TODO: add support for multiple line tasks
 -- TODO: undoing tasks, if task is marked as done, and has `done` label, it should replace done with `undone`
 -- TODO: sort tasks under `# Tasks`, and move tasks with `#next` tag, on top
 -- TODO: show the progress of tasks(if task has subtasks, show in virtual text how many of them is done)
 --       sub tasks should be only archived with the parent task
+
+---@param fpath string
+---@return string
+local function file_name_from_path(fpath)
+  return fpath:match "^.+/(.+)$" or fpath
+end
+
+---@param short_name string
+---@return string?
+local function full_file_path_from_short_name(short_name)
+  for _, fname in ipairs(config.task_files) do
+    if file_name_from_path(fname) == short_name .. ".md" then
+      return fname
+    end
+  end
+  return nil
+end
 
 ---@return string
 local function get_done_label()
···
 
 ---@param str string
 ---@return boolean
+local function has_next_tag(str)
+  return str:match "%#next" ~= nil
+end
+
+---@param str string
+---@return boolean
 local function check_task_status(str)
   return str:match "^(%s*%- )%[x%]" ~= nil
+end
+
+---@param str string
+---@return string
+local function remove_task_prefix(str)
+  local res = str:gsub("^%- %[ %] ", "")
+  return res
+end
+
+---@param fname string
+---@param line number
+---@return string
+local function display_file(fname, line)
+  local str = "" .. (fname:match "^(.-)%.%w+$" or fname) .. ":" .. line
+  return (str .. string.rep(" ", 14 - #str))
 end
 
 -- converts a like with markdown task to completed task, and removes `#next` in it, if there's one
···
 
 local tasks = {}
 
-function tasks.list_undone()
-  error "unimplemented"
-end
+function tasks.agenda()
+  -- parse all `task_files` for `#next` tag
+  --  FIXME: that's probably should be cached
 
-function tasks.list_done()
-  error "unimplemented"
+  ---@type table<string, {task: string, line: number}[]>
+  local agenda_tasks = {}
+  for _, fname in ipairs(config.task_files) do
+    local lines = vim.fn.readfile(fname)
+    for i, line in ipairs(lines) do
+      if is_task(line) and has_next_tag(line) then
+        local short_name = file_name_from_path(fname)
+        agenda_tasks[short_name] = agenda_tasks[short_name] or {}
+        table.insert(agenda_tasks[short_name], { task = line, line = i })
+      end
+    end
+  end
+
+  -- build the output
+  local output = { "# Agenda" }
+  for fname, ftasks in pairs(agenda_tasks) do
+    for _, ftask in pairs(ftasks) do
+      table.insert(
+        output,
+        display_file(fname, ftask.line) .. " " .. remove_task_prefix(ftask.task)
+      )
+    end
+  end
+
+  -- open the agenda view
+  vim.cmd.new()
+  local buf = vim.api.nvim_get_current_buf()
+  vim.api.nvim_buf_set_name(buf, "scratch.tasks:agenda")
+  vim.api.nvim_set_option_value("filetype", "markdown", { buf = buf })
+  vim.api.nvim_set_option_value("bufhidden", "wipe", { buf = buf })
+  vim.api.nvim_set_option_value("buftype", "nofile", { buf = buf })
+  vim.api.nvim_set_option_value("swapfile", false, { buf = buf })
+  vim.api.nvim_buf_set_lines(buf, 0, -1, false, output)
+  vim.api.nvim_set_option_value("modifiable", false, { buf = buf })
+  vim.api.nvim_exec_autocmds("FileType", { buffer = buf }) -- loads the ftplugins
+  vim.api.nvim_win_set_height(0, 10)
+  vim.api.nvim_win_set_cursor(0, { 2, 0 })
+
+  -- FIXME: this should be a separate function
+  vim.keymap.set("n", "<CR>", function()
+    local line = vim.api.nvim_get_current_line()
+    local fname, lineno = line:match "^([^:]+):(%d+)"
+    if fname == nil or lineno == nil then
+      vim.notify(
+        "No file name or line number found in the line",
+        vim.log.levels.WARN
+      )
+      return
+    end
+
+    local fpath = full_file_path_from_short_name(fname)
+    if fpath == nil then
+      vim.notify("No file name found in the line", vim.log.levels.WARN)
+      return
+    end
+
+    vim.cmd.edit(fpath)
+    vim.api.nvim_win_set_cursor(0, { tonumber(lineno), 0 })
+  end, { buffer = buf, desc = "Open file under cursor", silent = true })
 end
+
+tasks.agenda()
 
 function tasks.complete()
   vim.cmd.mkview() -- saves current folds/scroll