feat(sync): s3 backend (#112)

* feat(s3): create bucket interactively during auth when unconfigured

Problem: when a user runs `:Pending s3 auth` with no bucket configured,
auth succeeds but offers no way to create the bucket. The user must
manually run `aws s3api create-bucket` and update their config.

Solution: add `util.input()` coroutine-aware prompt wrapper and a
`create_bucket()` flow in `s3.lua` that prompts for bucket name and
region, handles the `us-east-1` LocationConstraint quirk, and logs a
config snippet on success. Called automatically from `auth()` when
`sync.s3.bucket` is absent.

* ci: typing

lua/pending/sync/s3.lua

@@ -66,6 +66,49 @@ local function ensure_sync_id(task)
   return sync_id
 end
 
+local function create_bucket()
+  local name = util.input({ prompt = 'S3 bucket name: ', default = 'pending.nvim' })
+  if not name or name == '' then
+    log.info('s3: bucket creation cancelled')
+    return
+  end
+
+  local region_cmd = base_cmd()
+  vim.list_extend(region_cmd, { 'configure', 'get', 'region' })
+  local region_result = util.system(region_cmd, { text = true })
+  local default_region = 'us-east-1'
+  if region_result.code == 0 and region_result.stdout then
+    local detected = vim.trim(region_result.stdout)
+    if detected ~= '' then
+      default_region = detected
+    end
+  end
+
+  local region = util.input({ prompt = 'AWS region: ', default = default_region })
+  if not region or region == '' then
+    region = 'us-east-1'
+  end
+
+  local cmd = base_cmd()
+  vim.list_extend(cmd, { 's3api', 'create-bucket', '--bucket', name, '--region', region })
+  if region ~= 'us-east-1' then
+    vim.list_extend(cmd, { '--create-bucket-configuration', 'LocationConstraint=' .. region })
+  end
+
+  local result = util.system(cmd, { text = true })
+  if result.code == 0 then
+    log.info(
+      's3: bucket created. Add to your config:\n  sync = { s3 = { bucket = "'
+        .. name
+        .. '", region = "'
+        .. region
+        .. '" } }'
+    )
+  else
+    log.error('s3: bucket creation failed — ' .. (result.stderr or 'unknown error'))
+  end
+end
+
 ---@param args? string
 ---@return nil
 function M.auth(args)
@@ -96,6 +139,10 @@ function M.auth(args)
       else
         log.info('s3: credentials valid')
       end
+      local s3cfg = get_config()
+      if not s3cfg or not s3cfg.bucket then
+        create_bucket()
+      end
     else
       local stderr = result.stderr or ''
       if stderr:find('SSO') or stderr:find('sso') then

lua/pending/sync/util.lua

@@ -35,6 +35,21 @@ function M.system(args, opts)
   return coroutine.yield() --[[@as { code: integer, stdout: string, stderr: string }]]
 end
 
+---@param opts? {prompt?: string, default?: string}
+---@return string?
+function M.input(opts)
+  local co = coroutine.running()
+  if not co then
+    error('util.input() must be called inside a coroutine')
+  end
+  vim.ui.input(opts or {}, function(result)
+    vim.schedule(function()
+      coroutine.resume(co, result)
+    end)
+  end)
+  return coroutine.yield() --[[@as string?]]
+end
+
 ---@param name string
 ---@param fn fun(): nil
 function M.with_guard(name, fn)

spec/s3_spec.lua

@@ -99,6 +99,28 @@ describe('s3', function()
       assert.truthy(msg and msg:find('authenticated'))
     end)
 
+    it('skips bucket creation when bucket is configured', function()
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123456","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      local orig_input = util.input
+      local input_called = false
+      util.input = function()
+        input_called = true
+        return nil
+      end
+      s3.auth()
+      util.input = orig_input
+      assert.is_false(input_called)
+    end)
+
     it('detects SSO expiry', function()
       util.system = function(args)
         if vim.tbl_contains(args, 'get-caller-identity') then
@@ -133,6 +155,225 @@ describe('s3', function()
     end)
   end)
 
+  describe('auth bucket creation', function()
+    local orig_input
+
+    before_each(function()
+      vim.g.pending = { data_path = tmpdir .. '/tasks.json', sync = { s3 = {} } }
+      config.reset()
+      package.loaded['pending'] = nil
+      package.loaded['pending.sync.s3'] = nil
+      pending = require('pending')
+      s3 = require('pending.sync.s3')
+      orig_input = util.input
+    end)
+
+    after_each(function()
+      util.input = orig_input
+    end)
+
+    it('prompts for bucket when none configured', function()
+      local input_calls = {}
+      util.input = function(opts)
+        table.insert(input_calls, opts)
+        if opts.prompt:find('bucket') then
+          return 'my-bucket'
+        end
+        return opts.default
+      end
+      local create_args
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        if vim.tbl_contains(args, 'configure') then
+          return { code = 0, stdout = 'us-west-2\n', stderr = '' }
+        end
+        if vim.tbl_contains(args, 'create-bucket') then
+          create_args = args
+          return { code = 0, stdout = '', stderr = '' }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      local msg
+      local orig_notify = vim.notify
+      vim.notify = function(m)
+        msg = m
+      end
+      s3.auth()
+      vim.notify = orig_notify
+      assert.equals(2, #input_calls)
+      assert.is_not_nil(create_args)
+      assert.truthy(vim.tbl_contains(create_args, 'my-bucket'))
+      assert.truthy(msg and msg:find('bucket created'))
+    end)
+
+    it('cancels when user provides empty bucket name', function()
+      util.input = function(opts)
+        if opts.prompt:find('bucket') then
+          return nil
+        end
+        return opts.default
+      end
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      local msg
+      local orig_notify = vim.notify
+      vim.notify = function(m)
+        msg = m
+      end
+      s3.auth()
+      vim.notify = orig_notify
+      assert.truthy(msg and msg:find('cancelled'))
+    end)
+
+    it('omits LocationConstraint for us-east-1', function()
+      util.input = function(opts)
+        if opts.prompt:find('bucket') then
+          return 'my-bucket'
+        end
+        if opts.prompt:find('region') then
+          return 'us-east-1'
+        end
+        return opts.default
+      end
+      local create_args
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        if vim.tbl_contains(args, 'configure') then
+          return { code = 0, stdout = 'us-east-1\n', stderr = '' }
+        end
+        if vim.tbl_contains(args, 'create-bucket') then
+          create_args = args
+          return { code = 0, stdout = '', stderr = '' }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      s3.auth()
+      assert.is_not_nil(create_args)
+      local joined = table.concat(create_args, ' ')
+      assert.falsy(joined:find('LocationConstraint'))
+    end)
+
+    it('includes LocationConstraint for non-us-east-1 regions', function()
+      util.input = function(opts)
+        if opts.prompt:find('bucket') then
+          return 'my-bucket'
+        end
+        if opts.prompt:find('region') then
+          return 'eu-west-1'
+        end
+        return opts.default
+      end
+      local create_args
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        if vim.tbl_contains(args, 'configure') then
+          return { code = 0, stdout = 'eu-west-1\n', stderr = '' }
+        end
+        if vim.tbl_contains(args, 'create-bucket') then
+          create_args = args
+          return { code = 0, stdout = '', stderr = '' }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      s3.auth()
+      assert.is_not_nil(create_args)
+      assert.truthy(vim.tbl_contains(create_args, 'LocationConstraint=eu-west-1'))
+    end)
+
+    it('reports error on bucket creation failure', function()
+      util.input = function(opts)
+        if opts.prompt:find('bucket') then
+          return 'bad-bucket'
+        end
+        return opts.default
+      end
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        if vim.tbl_contains(args, 'configure') then
+          return { code = 0, stdout = 'us-east-1\n', stderr = '' }
+        end
+        if vim.tbl_contains(args, 'create-bucket') then
+          return { code = 1, stdout = '', stderr = 'BucketAlreadyExists' }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      local msg
+      local orig_notify = vim.notify
+      vim.notify = function(m, level)
+        if level == vim.log.levels.ERROR then
+          msg = m
+        end
+      end
+      s3.auth()
+      vim.notify = orig_notify
+      assert.truthy(msg and msg:find('bucket creation failed'))
+    end)
+
+    it('defaults region to us-east-1 when aws configure returns nothing', function()
+      util.input = function(opts)
+        if opts.prompt:find('bucket') then
+          return 'my-bucket'
+        end
+        return ''
+      end
+      local create_args
+      util.system = function(args)
+        if vim.tbl_contains(args, 'get-caller-identity') then
+          return {
+            code = 0,
+            stdout = '{"Account":"123","Arn":"arn:aws:iam::user/test"}',
+            stderr = '',
+          }
+        end
+        if vim.tbl_contains(args, 'configure') then
+          return { code = 1, stdout = '', stderr = '' }
+        end
+        if vim.tbl_contains(args, 'create-bucket') then
+          create_args = args
+          return { code = 0, stdout = '', stderr = '' }
+        end
+        return { code = 0, stdout = '', stderr = '' }
+      end
+      s3.auth()
+      assert.is_not_nil(create_args)
+      assert.truthy(vim.tbl_contains(create_args, 'us-east-1'))
+      local joined = table.concat(create_args, ' ')
+      assert.falsy(joined:find('LocationConstraint'))
+    end)
+  end)
+
   describe('push', function()
     it('uploads store to S3', function()
       local s = pending.store()

spec/sync_util_spec.lua

@@ -80,7 +80,6 @@ describe('sync util', function()
       vim.g.pending = { data_path = tmpdir .. '/tasks.json' }
       config.reset()
       package.loaded['pending'] = nil
-      local pending = require('pending')
 
       local s = store_mod.new(tmpdir .. '/tasks.json')
       s:load()