-------------------------------------------------------------------------------
-- Tools to deal with notes
-------------------------------------------------------------------------------
local Notes = {}

local Util = require('util')
local Configuration = require('configuration')
local api = vim.api
-------------------------------------------------------------------------------
-- Internal Functions
-------------------------------------------------------------------------------
local templates = {
  daily = '%Y-%m-%d',
  weekly = '%Y-w%V',
  monthly = '%Y-%m',
  yearly = '%Y'
}

local patterns = {
  daily = '^(%d+)-(%d+)-(%d+).md$',
  weekly = '^(%d+)-w(%d+).md$',
  monthly = '^(%d+)-(%d+).md$',
  seasonal = '^(%d+)-s(%d+).md$',
  yearly = '^(%d+).md$'
}

local function open_or_create_from_template(type, file_path)

  local journal_file = io.open(file_path, 'r')
  if not journal_file then
    local template_contents = Configuration.load_template(type)

    journal_file = io.open(file_path, 'w')
    journal_file:write(template_contents)
    journal_file:close()
  end
  vim.cmd('edit ' .. file_path)
end

local function open_periodic_note(type, filename)
  local file_directory_path = Configuration.path_for(Configuration.configuration.periodic_locations[type])

  Util.ensure_directory_exists(file_directory_path)
  local file_path = Util.join(file_directory_path, filename)

  open_or_create_from_template(type, file_path)
end

local function find_next(type, filename, go_back_in_time)
  local multiplier = 1
  if go_back_in_time then
    multiplier = -1
  end

  local pattern = patterns[type]
  local year, second_match, day = filename:match(pattern)
  year = tonumber(year)

  -- Depending on context, second_match is either month, week, or season.
  if second_match then
    second_match = tonumber(second_match)
  end

  if day then
    day = tonumber(day)
  end

  local next = nil

  if type == 'daily' and year and second_match and day then
    next = os.date(templates.daily, os.time({
      year = year,
      month = second_match,
      day = day
    }) + multiplier * 24 * 60 * 60)
  elseif type == 'weekly' and year and second_match then
    -- According to ISO, the first week is the one that contains january 4
    local first_day_of_the_week = os.time({year = year, month = 1, day = 4})
    if multiplier < 0 then
      second_match = second_match - 2
    end
    next = os.date(templates.weekly, first_day_of_the_week + second_match * 7 * 24 * 60 * 60)
  elseif type == 'monthly' and year and second_match then
    next = os.date(templates.monthly, os.time({
      year = year,
      month = second_match + multiplier,
      day = 1
    }))
  elseif type == 'seasonal' and year and second_match then
    if multiplier > 0 and second_match == 4 then
      year = year + 1
    end
    if multiplier < 0 and second_match == 1 then
      year = year - 1
    end
    if multiplier > 0 then
      second_match = (second_match % 4) + 1
    else
      second_match = (second_match + 2) % 4 + 1
    end
    next = year .. '-s' .. second_match
  elseif type == 'yearly' and year then
    next = os.date(templates.yearly, os.time({
      year = year + multiplier,
      month = 1,
      day = 1
    }))
  end

  if next then
    Notes['open_' .. type](next)
  end
end

-------------------------------------------------------------------------------
-- Public Interface
-------------------------------------------------------------------------------

--- Opens the daily note
function Notes.open_daily(date)
  if not date or date == '' then
    date = os.date(templates.daily)
  end
  local filename =  date .. '.md'
  open_periodic_note('daily', filename)
end

--- Opens the weekly note
function Notes.open_weekly(date)
  if not date or date == '' then
    date = os.date(templates.weekly)
  end
  local filename = date .. '.md'
  open_periodic_note('weekly', filename)
end

--- Opens the monthly note
function Notes.open_monthly(date)
  if not date or date == '' then
    date = os.date(templates.monthly)
  end
  local filename = date .. '.md'
  open_periodic_note('monthly', filename)
end

--- Opens the seasonal note
function Notes.open_seasonal(date)
  if not date or date == '' then
    local year = os.date('%Y')
    local month = tonumber(os.date('%m'))
    local season = math.ceil(month / 3)
    date = year .. '-s' .. season
  end

  local filename = date .. '.md'
  open_periodic_note('seasonal', filename)
end

--- Opens the yearly note
function Notes.open_yearly(date)
  if not date or date == '' then
    date = os.date(templates.yearly)
  end
  local filename = date .. '.md'
  open_periodic_note('yearly', filename)
end

--- Opens the next note
function Notes.open_next()
  local filename = vim.fn.expand('%:t')
  for type, pattern in pairs(patterns) do
    if filename:match(pattern) ~= nil then
      return find_next(type, filename)
    end
  end
  api.nvim_err_writeln('Opening next only works on periodic notes.')
end

--- Opens the previous note
function Notes.open_previous()
  local filename = vim.fn.expand('%:t')
  for type, pattern in pairs(patterns) do
    if filename:match(pattern) ~= nil then
      return find_next(type, filename, true)
    end
  end
  api.nvim_err_writeln('Opening previous only works on periodic notes.')
end

--- Opens an arbitrary note
function Notes.open()
  local success, module = pcall(require, 'fzf-lua')
  if success then
    local notes_path = Configuration.path_for()
    Util.ensure_directory_exists(notes_path)
    module.files({ cwd = notes_path })
  else
    api.nvim_err_writeln('This feature requires optional dependency fzf-lua')
  end
end

return Notes