pending.nvim/lua/pending/sync/gcal.lua

local config = require('pending.config')
local log = require('pending.log')
local oauth = require('pending.sync.oauth')

local M = {}

M.name = 'gcal'

local BASE_URL = 'https://www.googleapis.com/calendar/v3'

---@param access_token string
---@return table<string, string>? name_to_id
---@return string? err
local function get_all_calendars(access_token)
  local data, err = oauth.curl_request(
    'GET',
    BASE_URL .. '/users/me/calendarList',
    oauth.auth_headers(access_token)
  )
  if err then
    return nil, err
  end
  local result = {}
  for _, item in ipairs(data and data.items or {}) do
    if item.summary then
      result[item.summary] = item.id
    end
  end
  return result, nil
end

---@param access_token string
---@param name string
---@param existing table<string, string>
---@return string? calendar_id
---@return string? err
local function find_or_create_calendar(access_token, name, existing)
  if existing[name] then
    return existing[name], nil
  end
  local body = vim.json.encode({ summary = name })
  local created, err =
    oauth.curl_request('POST', BASE_URL .. '/calendars', oauth.auth_headers(access_token), body)
  if err then
    return nil, err
  end
  local id = created and created.id
  if id then
    existing[name] = id
  end
  return id, nil
end

---@param date_str string
---@return string
local function next_day(date_str)
  local y, m, d = date_str:match('^(%d%d%d%d)-(%d%d)-(%d%d)')
  local t = os.time({ year = tonumber(y) or 0, month = tonumber(m) or 0, day = tonumber(d) or 0 })
    + 86400
  return os.date('%Y-%m-%d', t) --[[@as string]]
end

---@param access_token string
---@param calendar_id string
---@param task pending.Task
---@return string? event_id
---@return string? err
local function create_event(access_token, calendar_id, task)
  local event = {
    summary = task.description,
    start = { date = task.due },
    ['end'] = { date = next_day(task.due or '') },
    transparency = 'transparent',
    extendedProperties = {
      private = { taskId = tostring(task.id) },
    },
  }
  local data, err = oauth.curl_request(
    'POST',
    BASE_URL .. '/calendars/' .. oauth.url_encode(calendar_id) .. '/events',
    oauth.auth_headers(access_token),
    vim.json.encode(event)
  )
  if err then
    return nil, err
  end
  return data and data.id, nil
end

---@param access_token string
---@param calendar_id string
---@param event_id string
---@param task pending.Task
---@return string? err
local function update_event(access_token, calendar_id, event_id, task)
  local event = {
    summary = task.description,
    start = { date = task.due },
    ['end'] = { date = next_day(task.due or '') },
    transparency = 'transparent',
  }
  local _, err = oauth.curl_request(
    'PATCH',
    BASE_URL
      .. '/calendars/'
      .. oauth.url_encode(calendar_id)
      .. '/events/'
      .. oauth.url_encode(event_id),
    oauth.auth_headers(access_token),
    vim.json.encode(event)
  )
  return err
end

---@param access_token string
---@param calendar_id string
---@param event_id string
---@return string? err
local function delete_event(access_token, calendar_id, event_id)
  local _, err = oauth.curl_request(
    'DELETE',
    BASE_URL
      .. '/calendars/'
      .. oauth.url_encode(calendar_id)
      .. '/events/'
      .. oauth.url_encode(event_id),
    oauth.auth_headers(access_token)
  )
  return err
end

---@return boolean
local function allow_remote_delete()
  local cfg = config.get()
  local sync = cfg.sync or {}
  local per = (sync.gcal or {}) --[[@as pending.GcalConfig]]
  if per.remote_delete ~= nil then
    return per.remote_delete == true
  end
  return sync.remote_delete == true
end

---@param task pending.Task
---@param extra table
---@param now_ts string
local function unlink_remote(task, extra, now_ts)
  extra['_gcal_event_id'] = nil
  extra['_gcal_calendar_id'] = nil
  if next(extra) == nil then
    task._extra = nil
  else
    task._extra = extra
  end
  task.modified = now_ts
end

---@param parts {[1]: integer, [2]: string}[]
---@return string
local function fmt_counts(parts)
  local items = {}
  for _, p in ipairs(parts) do
    if p[1] > 0 then
      table.insert(items, p[1] .. ' ' .. p[2])
    end
  end
  if #items == 0 then
    return 'nothing to do'
  end
  return table.concat(items, ' | ')
end

function M.push()
  oauth.with_token(oauth.google_client, 'gcal', function(access_token)
    local calendars, cal_err = get_all_calendars(access_token)
    if cal_err or not calendars then
      log.error(cal_err or 'failed to fetch calendars')
      return
    end

    local s = require('pending').store()
    local now_ts = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]]
    local created, updated, deleted, failed = 0, 0, 0, 0

    for _, task in ipairs(s:tasks()) do
      local extra = task._extra or {}
      local event_id = extra['_gcal_event_id'] --[[@as string?]]
      local cal_id = extra['_gcal_calendar_id'] --[[@as string?]]

      local should_delete = event_id ~= nil
        and cal_id ~= nil
        and (
          task.status == 'done'
          or task.status == 'deleted'
          or (task.status == 'pending' and not task.due)
        )

      if should_delete then
        if allow_remote_delete() then
          local del_err =
            delete_event(access_token, cal_id --[[@as string]], event_id --[[@as string]])
          if del_err then
            log.warn('gcal delete failed: ' .. del_err)
            failed = failed + 1
          else
            unlink_remote(task, extra, now_ts)
            deleted = deleted + 1
          end
        else
          log.debug(
            'gcal: remote delete skipped (remote_delete disabled) — unlinked task #' .. task.id
          )
          unlink_remote(task, extra, now_ts)
          deleted = deleted + 1
        end
      elseif task.status == 'pending' and task.due then
        local cat = task.category or config.get().default_category
        if event_id and cal_id then
          local upd_err = update_event(access_token, cal_id, event_id, task)
          if upd_err then
            log.warn('gcal update failed: ' .. upd_err)
            failed = failed + 1
          else
            updated = updated + 1
          end
        else
          local lid, lid_err = find_or_create_calendar(access_token, cat, calendars)
          if lid_err or not lid then
            log.warn('gcal calendar failed: ' .. (lid_err or 'unknown'))
            failed = failed + 1
          else
            local new_id, create_err = create_event(access_token, lid, task)
            if create_err then
              log.warn('gcal create failed: ' .. create_err)
              failed = failed + 1
            elseif new_id then
              if not task._extra then
                task._extra = {}
              end
              task._extra['_gcal_event_id'] = new_id
              task._extra['_gcal_calendar_id'] = lid
              task.modified = now_ts
              created = created + 1
            end
          end
        end
      end
    end

    s:save()
    require('pending')._recompute_counts()
    local buffer = require('pending.buffer')
    if buffer.bufnr() and vim.api.nvim_buf_is_valid(buffer.bufnr()) then
      buffer.render(buffer.bufnr())
    end
    log.info('gcal push: ' .. fmt_counts({
      { created, 'added' },
      { updated, 'updated' },
      { deleted, 'removed' },
      { failed, 'failed' },
    }))
  end)
end

---@return nil
function M.health()
  oauth.health(M.name)
  local tokens = oauth.google_client:load_tokens()
  if tokens and tokens.refresh_token then
    vim.health.ok('gcal tokens found')
  else
    vim.health.info('no gcal tokens — run :Pending auth')
  end
end

return M