--- Personal lua config files for NeoVim.
--  Last Changed: 2019-01-27
--  Author: Federico Igne <git@federicoigne.com>
--  License: This file is placed in the public domain.

local zettel = {}

local api = vim.api
local cmd = vim.cmd
local exec = api.nvim_command
local base = vim.env.NOTES

--- Base directory of the Zettelkasten
zettel.base = base

--- Gets title of a zettel given the file
--
-- @param file name of the zettel file
-- @return title of the zettel
--
-- @note this assumes the second line of the zettel has the following
-- structure
--      title: <index> - <title>
local function get_title(file)
  local fp = io.open(base .. '/' .. file)
  fp:read()
  local line2 = fp:read()
  fp:close()
  if line2 then
    local _,t = line2:find(" - ", 1, true)
    if t then 
        return line2:sub(t+1)
    end
  end
  return "[Not a Zettel]"
end

--- Generate the markdown link to a given zettel
--
-- @param index index of the zettel
-- @param linenr optional line number. Can be `nil` (no line number), a
--        positive integer (line number), a negative integer (current
--        line number).
-- @return markdown link of the zettel
local function markdown_link(index, linenr)
  local linenr = linenr
  if not linenr then
    linenr = ''
  elseif linenr >= 0 then
    linenr = ' ' .. linenr
  else
    linenr = ' ' .. vim.api.nvim_win_get_cursor(0).row
  end
  return '[' .. index .. '](' .. index .. '.md' .. linenr .. ')'
end

--- Inserts a link to the given zettel in the current buffer
--
-- @param index index of the zettel
-- @param linenr optional line number. can be `nil` (no line number), a
--        positive integer (line number), a negative integer (current
--        line number).
-- @return inserted link
local function breadcrumb(index, linenr)
  local link = markdown_link(index, linenr)
  exec('normal a' .. link .. ' ')
  return link
end

--- Telescope action that inserts a markdown link and yanks.
--
-- @see Telescope documentation for more info on the signature.
local function yank_and_insert(line)
  return function(prompt_bufnr)
    local actions = require 'telescope.actions'
    local actions_state = require 'telescope.actions.state'
    -- Close Telescope buffer
    actions.close(prompt_bufnr)
    -- Get current entry from Telescope
    local entry = actions_state.get_selected_entry()
    -- Get line number
    local linenr = nil
    if line and entry.lnum then
      linenr = entry.lnum
    end
    -- Yank to `z` and insert the markdown link to the entry
    vim.fn.setreg('z', breadcrumb(entry.value, linenr))
  end
end

--- Create a new zettel
--
-- @param bang leave a link to the new note where the cursor was
--        originally (if set to > 0).
-- @param mods mods applied to the new split (see `:h <mods>`)
-- @param ... title of the new zettel
function zettel.new(bang, mods, ...)
  local index = vim.fn.strftime('%Y%m%d%H%M')
  local fullpath = base .. '/' .. index .. '.md'
  -- Leave breadcrumb (link to new note)
  if bang > 0 then
      breadcrumb(index)
  end
  -- Edit the note in a new window (and change the local pwd)
  exec(mods .. ' new +lcd\\ ' .. base .. ' ' .. fullpath)
  -- Load template
  exec('0read ' .. base .. '/.template.md')
  -- Fill in title
  local title = table.concat({...}, ' ')
  if title:len() == 0 then
    title = '<+title+>'
  end
  exec('2s/^title:.*$/title: ' .. index .. ' - ' .. title .. '/')
  exec('nohlsearch')
end

--- Open the Zettelkasten index.
--
-- @param mods mods applied to the new split (see `:h <mods>`)
function zettel.kasten(mods)
  -- Edit the note in a new window (and change the local pwd)
  local fullpath = base .. '/index.md'
  exec(mods .. ' new +lcd\\ ' .. base .. ' ' .. fullpath)
end

--- Grab a markdown link of the current open zettel
--
-- @param line if > 0 include the current line in the link
-- @param reg yank to specific register (defaults to `z`)
function zettel.link_yank(line, reg)
  local index = vim.fn.expand('%:t:r')
  local reg = reg
  if not reg or reg:len() == 0 then
    reg = 'z'
  end
  local linenr = nil
  if line > 0 then
      linenr = -1
  end
  vim.fn.setreg(reg, markdown_link(index, linenr))
end

--- (File) Telescope into the zettelkasten
--
-- Modifies version of the `find_files` builtin to search into the
-- zettelkasten.
function zettel.find_files()
  require('telescope.builtin').find_files {
    -- Search in zettelkasten
    cwd = base,
    -- Do not search recursively
    -- Note that this assumes `rg` is available in the system
    find_command = { 'rg', '--files', '--glob', '/*.md' },
    -- Additional mappings
    attach_mappings = function(prompt_bufnr, map)
      map('i', '<C-y>', yank_and_insert(false))
      return true
    end,
    -- Custom entry maker
    entry_maker = function(entry)
      local title = get_title(entry)
      return {
        value = entry:gsub('%.md$', ''), -- entry value (see actions)
        path = base .. '/' .. entry,     -- path used for preview
        text = title,
        display = title,                 -- displayed on the matching list
        ordinal = title,                 -- what the prompt is matched against
      }
    end,
  }
end

--- (Grep) Telescope into the zettelkasten
--
-- Modifies version of the `live_grep` builtin to search into the
-- zettelkasten.
function zettel.live_grep(mappings)
  require('telescope.builtin').live_grep {
    -- Search in zettelkasten
    cwd = base,
    -- Do not search recursively
    glob_pattern = '/*.md',
    -- Additional mappings
    attach_mappings = function(prompt_bufnr, map)
      map('i', '<C-y>', yank_and_insert(false))
      map('i', '<C-Y>', yank_and_insert(true))
      return true
    end
  }
end

--- Returns the path of the resource folder for the current zettel.
function zettel.resources()
  return 'resources/' .. vim.fn.expand('%:t:r') .. '/'
end

--- Opens the resource path in nnn.
--
-- It creates the necessary directory structure if necessary.
function zettel.open_resources()
  local dir = zettel.base .. '/' .. zettel.resources()
  -- Create directory if not existent
  vim.fn.system({'mkdir', '-p', dir})
  -- Open resource directory in nnn
  cmd.NnnPicker(dir)
end

--- Setup zettel-specific mappings and options.
function zettel.setup()
  local map = require 'dyamon.util.map'

  cmd([[
    command! -buffer ZResources call v:lua.dyamon.zettel.open_resources()
    command! -buffer ZTitle call v:lua.dyamon.zettel.hover_title()
    command! -bang -buffer ZLink call v:lua.dyamon.zettel.link_yank(<bang>0)
  ]])

  map.b.nore.n(0, '<leader>zr', '<cmd>ZResources<cr>', opts)
  map.b.nore.n(0, 'K', '<cmd>ZTitle<cr>', opts)
  map.b.nore.i(0, ';zr', zettel.resources(), opts)
end

--- Compute inbound links of a zettel
--
-- @param zettel filename of a zettel (defaults to current one)
function zettel.inbound(zettel)
  local zettel = zettel or vim.fn.expand('%:t')
  return vim.fn.systemlist('rg --files-with-matches --glob /*.md "' .. zettel)
end

--- Compute outbound links of a zettel
--
-- @param zettel filename of a zettel (defaults to current one)
function zettel.outbound()
  local zettel = zettel or vim.fn.expand('%:t')
  return vim.fn.systemlist('rg -oN "[0-9]+.md" ' .. zettel .. ' | sort | uniq')
end

--- Statusbar indicator
function zettel.status()
  if vim.bo.filetype:find('zettel') then
    return ' <' .. table.getn(zettel.inbound()) .. ',' .. table.getn(zettel.outbound()) .. '> '
  end
  return ''
end

return zettel