local api = vim.api
local nvim_on = require('vim._core.util').nvim_on
local bit = require('bit')
local util = require('vim.lsp.util')
local Range = require('vim.treesitter._range')
local uv = vim.uv

local Capability = require('vim.lsp._capability')

local M = {}

--- @class (private) STTokenRange
--- @field line integer line number 0-based
--- @field start_col integer start column 0-based
--- @field end_line integer end line number 0-based
--- @field end_col integer end column 0-based
--- @field type string token type as string
--- @field modifiers table<string,boolean> token modifiers as a set. E.g., { static = true, readonly = true }
--- @field marked boolean whether this token has had extmarks applied

--- @class (private) STCurrentResult
--- @field version? integer document version associated with this result
--- @field result_id? string resultId from the server; used with delta requests
--- @field highlights? STTokenRange[] cache of highlight ranges for this document version
--- @field tokens? uinteger[] raw token array as received by the server. used for calculating delta responses
--- @field namespace_cleared? boolean whether the namespace was cleared for this result yet

--- @class (private) STActiveRequest
--- @field request_id? integer the LSP request ID of the most recent request sent to the server
--- @field version? integer the document version associated with the most recent request

--- @class (private) STClientState
--- @field namespace integer
--- @field supports_range boolean
--- @field supports_delta boolean
--- @field active_request STActiveRequest
--- @field active_range_request STActiveRequest
--- @field current_result STCurrentResult
--- @field timer uv.uv_timer_t? uv_timer for debouncing requests for new tokens
--- @field has_full_result boolean

---@class (private) STHighlighter : vim.lsp.Capability
---@field active table<integer, STHighlighter>
---@field debounce integer milliseconds to debounce requests for new tokens
---@field client_state table<integer, STClientState>
local STHighlighter = {
  name = 'semantic_tokens',
  method = 'textDocument/semanticTokens',
  debounce = 200,
  active = {},
}
STHighlighter.__index = STHighlighter
setmetatable(STHighlighter, Capability)
Capability.all[STHighlighter.name] = STHighlighter

--- Extracts modifier strings from the encoded number in the token array
---
---@param x integer
---@param modifiers_table table<integer,string>
---@return table<string, boolean>
local function modifiers_from_number(x, modifiers_table)
  local modifiers = {} ---@type table<string,boolean>
  local idx = 1
  while x > 0 do
    if bit.band(x, 1) == 1 then
      modifiers[modifiers_table[idx]] = true
    end
    x = bit.rshift(x, 1)
    idx = idx + 1
  end

  return modifiers
end

--- Converts a raw token list to a list of highlight ranges used by the on_win callback
---
---@async
---@param data integer[]
---@param bufnr integer
---@param client vim.lsp.Client
---@param request STActiveRequest
---@param ranges STTokenRange[]
---@return STTokenRange[]
local function tokens_to_ranges(data, bufnr, client, request, ranges)
  local legend = client.server_capabilities.semanticTokensProvider.legend
  local token_types = legend.tokenTypes
  local token_modifiers = legend.tokenModifiers
  local encoding = client.offset_encoding
  local lines = api.nvim_buf_get_lines(bufnr, 0, -1, false)
  -- For all encodings, \r\n takes up two code points, and \n (or \r) takes up one.
  local eol_offset = vim.bo.fileformat[bufnr] == 'dos' and 2 or 1
  local version = request.version
  local request_id = request.request_id
  local last_insert_idx = 1

  local start = uv.hrtime()
  local ms_to_ns = 1e6
  local yield_interval_ns = 5 * ms_to_ns
  local co, is_main = coroutine.running()

  local line ---@type integer?
  local start_char = 0
  for i = 1, #data, 5 do
    -- if this function is called from the main coroutine, let it run to completion with no yield
    if not is_main then
      local elapsed_ns = uv.hrtime() - start

      if elapsed_ns > yield_interval_ns then
        vim.schedule(function()
          -- Ensure the request hasn't become stale since the last time the coroutine ran.
          -- If it's stale, we don't resume the coroutine so it'll be garbage collected.
          if
            version == util.buf_versions[bufnr]
            and request_id == request.request_id
            and api.nvim_buf_is_valid(bufnr)
          then
            coroutine.resume(co)
          end
        end)

        coroutine.yield()
        start = uv.hrtime()
      end
    end

    local delta_line = data[i]
    line = line and line + delta_line or delta_line
    local delta_start = data[i + 1]
    start_char = delta_line == 0 and start_char + delta_start or delta_start

    -- data[i+3] +1 because Lua tables are 1-indexed
    local token_type = token_types[data[i + 3] + 1]

    if token_type then
      local modifiers = modifiers_from_number(data[i + 4], token_modifiers)
      local end_char = start_char + data[i + 2] --- @type integer LuaLS bug
      local buf_line = lines[line + 1] or ''
      local end_line = line ---@type integer
      local start_col = vim.str_byteindex(buf_line, encoding, start_char, false)

      ---@type integer LuaLS bug, type must be marked explicitly here
      local new_end_char = end_char - vim.str_utfindex(buf_line, encoding) - eol_offset
      -- While end_char goes past the given line, extend the token range to the next line
      while new_end_char > 0 and end_line < #lines - 1 do
        end_char = new_end_char
        end_line = end_line + 1
        buf_line = lines[end_line + 1] or ''
        new_end_char = new_end_char - vim.str_utfindex(buf_line, encoding) - eol_offset
      end

      local end_col = vim.str_byteindex(buf_line, encoding, end_char, false)

      ---@type STTokenRange
      local range = {
        line = line,
        end_line = end_line,
        start_col = start_col,
        end_col = end_col,
        type = token_type,
        modifiers = modifiers,
        marked = false,
      }

      if last_insert_idx < #ranges then
        local needs_insert = true
        local idx = vim.list.bisect(ranges, { line = range.line }, {
          lo = last_insert_idx,
          key = function(highlight)
            return highlight.line
          end,
        })
        while idx <= #ranges do
          local token = ranges[idx]

          if
            token.line > range.line
            or (token.line == range.line and token.start_col > range.start_col)
          then
            break
          end

          if
            range.line == token.line
            and range.start_col == token.start_col
            and range.end_line == token.end_line
            and range.end_col == token.end_col
            and range.type == token.type
          then
            needs_insert = false
            break
          end

          idx = idx + 1
        end

        last_insert_idx = idx
        if needs_insert then
          table.insert(ranges, last_insert_idx, range)
        end
      else
        last_insert_idx = #ranges + 1
        ranges[last_insert_idx] = range
      end
    end
  end

  return ranges
end

---@package
function STHighlighter:new(bufnr)
  self = Capability.new(self, bufnr)

  nvim_on('LspNotify', self.augroup, { buf = self.bufnr }, function(opts)
    local client_id = opts.data.client_id ---@type integer

    if not self.client_state[client_id] then
      return
    end

    if opts.data.method == 'textDocument/didClose' then
      self:reset(client_id)
    end

    if
      opts.data.method == 'textDocument/didChange' or opts.data.method == 'textDocument/didOpen'
    then
      self:send_request(client_id)
    end
  end)

  nvim_on('BufWinEnter', self.augroup, { buf = self.bufnr }, function()
    for client_id, _ in pairs(self.client_state) do
      self:send_request(client_id)
    end
  end)

  nvim_on('WinScrolled', self.augroup, { buf = self.bufnr }, function()
    for client_id, state in pairs(self.client_state) do
      if state.supports_range then
        self:debounce_request(client_id)
      end
    end
  end)

  return self
end

---@package
function STHighlighter:on_attach(client_id)
  local client = vim.lsp.get_client_by_id(client_id)
  local state = self.client_state[client_id]
  if not state then
    state = {
      namespace = api.nvim_create_namespace('nvim.lsp.semantic_tokens:' .. client_id),
      supports_range = client
          and client:supports_method('textDocument/semanticTokens/range', self.bufnr)
        or false,
      supports_delta = client
          and client:supports_method('textDocument/semanticTokens/full/delta', self.bufnr)
        or false,
      active_request = {},
      active_range_request = {},
      current_result = {},
      has_full_result = false,
    }
    self.client_state[client_id] = state
  end

  self:send_request(client_id)
end

---@package
function STHighlighter:on_detach(client_id)
  local state = self.client_state[client_id]
  if state then
    --TODO: delete namespace if/when that becomes possible
    api.nvim_buf_clear_namespace(self.bufnr, state.namespace, 0, -1)
    self:reset_timer(state)
    self.client_state[client_id] = nil
  end
end

--- This is the entry point for getting all the tokens in a buffer.
---
--- For the given client, this sends semantic token requests to ask for semantic tokens. If the
--- server supports range requests and a full result has not been processed yet, it will send a
--- range request for the current visible range. Additionally, if a result for the current document
--- version hasn't been processed yet, it sends either a full or delta request, depending on what
--- the server supports and whether there's a current full result for the previous document version.
---
--- This function will skip full/delta requests on servers where there is an already an active
--- full/delta request in flight for the same version. If there is a stale request in flight, that
--- is cancelled prior to sending a new one.
---
--- Finally, for successful requests, the requestId (full/delta) and document version are saved to
--- facilitate document synchronization in the response.
---
---@package
---@param client_id integer
function STHighlighter:send_request(client_id)
  local client = vim.lsp.get_client_by_id(client_id)
  local state = self.client_state[client_id]

  if client and state then
    self:reset_timer(state)

    local version = util.buf_versions[self.bufnr]

    -- If the server supports range and there's no full result yet, then start with a range
    -- request
    if state.supports_range and not state.has_full_result then
      self:send_range_request(client, state, version)
    end

    if
      (not state.has_full_result or state.current_result.version ~= version)
      and state.active_request.version ~= version
    then
      self:send_full_delta_request(client, state, version)
    end
  end
end

--- Send a range request for the visible area
---
---@private
---@param client vim.lsp.Client
---@param state STClientState
---@param version integer
function STHighlighter:send_range_request(client, state, version)
  local active_request = state.active_range_request

  -- cancel stale in-flight request
  if active_request and active_request.request_id then
    client:cancel_request(active_request.request_id)
    active_request.request_id = nil
    active_request.version = nil
  end

  ---@type lsp.SemanticTokensRangeParams
  local params = {
    textDocument = util.make_text_document_params(self.bufnr),
    range = self:get_overscan_range(),
  }

  ---@type vim.lsp.protocol.Method.ClientToServer.Request
  local method = 'textDocument/semanticTokens/range'

  ---@param response? lsp.SemanticTokens
  local success, request_id = client:request(method, params, function(err, response, ctx)
    local bufnr = assert(ctx.bufnr)
    local highlighter = STHighlighter.active[bufnr]
    if not highlighter then
      return
    end

    -- Only process range response if we got a valid response and don't have a full result yet
    if err or not response or state.has_full_result then
      if err then
        vim.lsp.log.error('semantic_tokens', err)
      end
      active_request.request_id = nil
      active_request.version = nil
      return
    end

    coroutine.wrap(STHighlighter.process_response)(
      highlighter,
      response,
      client,
      ctx.request_id,
      version,
      true
    )
  end, self.bufnr)

  if success then
    active_request.request_id = request_id
    active_request.version = version
  end
end

--- Send a full or delta request
---
---@private
---@param client vim.lsp.Client
---@param state STClientState
---@param version integer
function STHighlighter:send_full_delta_request(client, state, version)
  local current_result = state.current_result
  local active_request = state.active_request

  -- cancel stale in-flight request
  if active_request.request_id then
    client:cancel_request(active_request.request_id)
    active_request.request_id = nil
    active_request.version = nil
  end

  ---@type lsp.SemanticTokensParams|lsp.SemanticTokensDeltaParams
  local params = { textDocument = util.make_text_document_params(self.bufnr) }

  ---@type vim.lsp.protocol.Method.ClientToServer.Request
  local method = 'textDocument/semanticTokens/full'

  if state.supports_delta and current_result.result_id then
    method = 'textDocument/semanticTokens/full/delta'
    params.previousResultId = current_result.result_id
  end

  ---@param response? lsp.SemanticTokens|lsp.SemanticTokensDelta
  local success, request_id = client:request(method, params, function(err, response, ctx)
    local bufnr = assert(ctx.bufnr)
    local highlighter = STHighlighter.active[bufnr]
    if not highlighter then
      return
    end

    if err or not response then
      if err then
        vim.lsp.log.error('semantic_tokens', err)
      end
      active_request.request_id = nil
      active_request.version = nil
      return
    end

    coroutine.wrap(STHighlighter.process_response)(
      highlighter,
      response,
      client,
      ctx.request_id,
      version,
      false
    )
  end, self.bufnr)

  if success then
    active_request.request_id = request_id
    active_request.version = version
  end
end

---@private
function STHighlighter:cancel_active_request(client_id)
  local state = assert(self.client_state[client_id])
  local client = vim.lsp.get_client_by_id(client_id)

  ---@param request STActiveRequest
  local function clear(request)
    if client and request.request_id then
      client:cancel_request(request.request_id)
      request.request_id = nil
      request.version = nil
    end
  end

  clear(state.active_range_request)
  clear(state.active_request)
end

--- Gets a range that encompasses all visible lines plus overscan across all windows
--- @private
--- @return lsp.Range
function STHighlighter:get_overscan_range()
  local wins = vim.fn.win_findbuf(self.bufnr)
  local num_lines = vim.api.nvim_buf_line_count(self.bufnr)
  local min_start, max_end = nil, nil

  for _, win in ipairs(wins) do
    local wininfo = vim.fn.getwininfo(win)[1]
    if wininfo then
      -- Overscan the token request by the height of the window on each side
      -- to prevent flickering when navigating up and down.
      local start_line = math.max(0, wininfo.topline - 1 - wininfo.height)
      local end_line = math.min(num_lines, wininfo.botline + wininfo.height)
      if not min_start or start_line < min_start then
        min_start = start_line
      end
      if not max_end or end_line > max_end then
        max_end = end_line
      end
    end
  end

  ---@type lsp.Range
  return {
    ['start'] = { line = min_start or 0, character = 0 },
    ['end'] = { line = max_end or 0, character = 0 },
  }
end

--- This function will parse the semantic token responses and set up the cache
--- (current_result). It also performs document synchronization by checking the
--- version of the document associated with the resulting request_id and only
--- performing work if the response is not out-of-date.
---
--- Delta edits are applied if necessary, and new highlight ranges are calculated
--- and stored in the buffer state.
---
--- Finally, a redraw command is issued to force nvim to redraw the screen to
--- pick up changed highlight tokens.
---
---@async
---@param response lsp.SemanticTokens|lsp.SemanticTokensDelta
---@param client vim.lsp.Client
---@param request_id integer
---@param version integer
---@param is_range_request boolean
---@private
function STHighlighter:process_response(response, client, request_id, version, is_range_request)
  local state = self.client_state[client.id]
  if not state then
    return
  end

  ---@type STActiveRequest
  local active_request
  if is_range_request then
    active_request = state.active_range_request
  else
    active_request = state.active_request
  end

  -- ignore stale responses
  if active_request.request_id and request_id ~= active_request.request_id then
    return
  end

  if not api.nvim_buf_is_valid(self.bufnr) then
    return
  end

  -- if we have a response to a delta request, update the state of our tokens
  -- appropriately. if it's a full response, just use that
  local tokens ---@type integer[]
  local token_edits = response.edits
  if token_edits then
    table.sort(token_edits, function(a, b)
      return a.start < b.start
    end)

    tokens = {} --- @type integer[]
    local old_tokens = assert(state.current_result.tokens)
    local idx = 1
    for _, token_edit in ipairs(token_edits) do
      vim.list_extend(tokens, old_tokens, idx, token_edit.start)
      if token_edit.data then
        vim.list_extend(tokens, token_edit.data)
      end
      idx = token_edit.start + token_edit.deleteCount + 1
    end
    vim.list_extend(tokens, old_tokens, idx)
  else
    tokens = response.data
  end

  local current_result = state.current_result
  local version_changed = version ~= current_result.version
  local highlights = {} --- @type STTokenRange[]
  if current_result.highlights and not version_changed then
    highlights = assert(current_result.highlights)
  end

  -- convert token list to highlight ranges
  -- this could yield and run over multiple event loop iterations
  highlights = tokens_to_ranges(tokens, self.bufnr, client, active_request, highlights)

  -- if this was a full result, mark the state as having processed it
  if not is_range_request then
    state.has_full_result = true
  end

  -- reset active request
  active_request.request_id = nil
  active_request.version = nil

  -- update the state with the new results
  current_result.version = version
  current_result.result_id = not is_range_request and response.resultId or nil
  current_result.tokens = tokens
  current_result.highlights = highlights
  if version_changed then
    current_result.namespace_cleared = false
  end

  -- redraw all windows displaying buffer
  if vim.fn.win_gettype(vim.fn.bufwinid(self.bufnr)) == '' then
    api.nvim__redraw({ buf = self.bufnr, valid = true })
  end
end

--- @param bufnr integer
--- @param ns integer
--- @param token STTokenRange
--- @param hl_group string
--- @param priority integer
local function set_mark(bufnr, ns, token, hl_group, priority)
  api.nvim_buf_set_extmark(bufnr, ns, token.line, token.start_col, {
    hl_group = hl_group,
    end_line = token.end_line,
    end_col = token.end_col,
    priority = priority,
    strict = false,
  })
end

--- @param lnum integer
--- @param foldend integer?
--- @return boolean, integer?
local function check_fold(lnum, foldend)
  if foldend and lnum <= foldend then
    return true, foldend
  end

  local folded = vim.fn.foldclosed(lnum)

  if folded == -1 then
    return false, nil
  end

  return folded ~= lnum, vim.fn.foldclosedend(lnum)
end

--- on_win handler for the decoration provider (see |nvim_set_decoration_provider|)
---
--- If there is a current result for the buffer and the version matches the
--- current document version, then the tokens are valid and can be applied. As
--- the buffer is drawn, this function will add extmark highlights for every
--- token in the range of visible lines. Once a highlight has been added, it
--- sticks around until the document changes and there's a new set of matching
--- highlight tokens available.
---
--- If this is the first time a buffer is being drawn with a new set of
--- highlights for the current document version, the namespace is cleared to
--- remove extmarks from the last version. It's done here instead of the response
--- handler to avoid the "blink" that occurs due to the timing between the
--- response handler and the actual redraw.
---
---@package
---@param topline integer
---@param botline integer
function STHighlighter:on_win(topline, botline)
  for client_id, state in pairs(self.client_state) do
    local current_result = state.current_result
    if current_result.version == util.buf_versions[self.bufnr] then
      if not current_result.namespace_cleared then
        api.nvim_buf_clear_namespace(self.bufnr, state.namespace, 0, -1)
        current_result.namespace_cleared = true
      end

      -- We can't use ephemeral extmarks because the buffer updates are not in
      -- sync with the list of semantic tokens. There's a delay between the
      -- buffer changing and when the LSP server can respond with updated
      -- tokens, and we don't want to "blink" the token highlights while
      -- updates are in flight, and we don't want to use stale tokens because
      -- they likely won't line up right with the actual buffer.
      --
      -- Instead, we have to use normal extmarks that can attach to locations
      -- in the buffer and are persisted between redraws.
      --
      -- `strict = false` is necessary here for the 1% of cases where the
      -- current result doesn't actually match the buffer contents. Some
      -- LSP servers can respond with stale tokens on requests if they are
      -- still processing changes from a didChange notification.
      --
      -- LSP servers that do this _should_ follow up known stale responses
      -- with a refresh notification once they've finished processing the
      -- didChange notification, which would re-synchronize the tokens from
      -- our end.
      --
      -- The server I know of that does this is clangd when the preamble of
      -- a file changes and the token request is processed with a stale
      -- preamble while the new one is still being built. Once the preamble
      -- finishes, clangd sends a refresh request which lets the client
      -- re-synchronize the tokens.

      local function set_mark0(token, hl_group, delta)
        set_mark(
          self.bufnr,
          state.namespace,
          token,
          hl_group,
          vim.hl.priorities.semantic_tokens + delta
        )
      end

      local ft = vim.bo[self.bufnr].filetype
      local highlights = assert(current_result.highlights)
      local first = vim.list.bisect(highlights, { end_line = topline }, {
        key = function(highlight)
          return highlight.end_line
        end,
      })
      local last = vim.list.bisect(highlights, { line = botline }, {
        lo = first,
        bound = 'upper',
        key = function(highlight)
          return highlight.line
        end,
      }) - 1

      --- @type boolean?, integer?
      local is_folded, foldend

      for i = first, last do
        local token = assert(highlights[i])

        is_folded, foldend = check_fold(token.line + 1, foldend)

        if not is_folded and not token.marked then
          set_mark0(token, string.format('@lsp.type.%s.%s', token.type, ft), 0)
          for modifier in pairs(token.modifiers) do
            set_mark0(token, string.format('@lsp.mod.%s.%s', modifier, ft), 1)
            set_mark0(token, string.format('@lsp.typemod.%s.%s.%s', token.type, modifier, ft), 2)
          end
          token.marked = true

          api.nvim_exec_autocmds('LspTokenUpdate', {
            buf = self.bufnr,
            modeline = false,
            data = {
              token = token,
              client_id = client_id,
            },
          })
        end
      end
    end
  end
end

--- Reset the buffer's highlighting state and clears the extmark highlights.
---
---@package
---@param client_id integer
function STHighlighter:reset(client_id)
  local state = assert(self.client_state[client_id])
  self:cancel_active_request(client_id)
  api.nvim_buf_clear_namespace(self.bufnr, state.namespace, 0, -1)
  state.current_result = {}
  state.has_full_result = false
end

--- Mark a client's results as dirty. This method will cancel any active
--- requests to the server and pause new highlights from being added
--- in the on_win callback. The rest of the current results are saved
--- in case the server supports delta requests.
---
---@package
---@param client_id integer
function STHighlighter:mark_dirty(client_id)
  local state = assert(self.client_state[client_id])

  -- if we clear the version from current_result, it'll cause the next
  -- full/delta request to be sent and will also pause new highlights
  -- from being added in on_win until a new result comes from the server
  if state.current_result then
    state.current_result.version = nil
  end

  -- clearing this flag will also allow range requests to fire to
  -- potentially get a faster result
  state.has_full_result = false

  self:cancel_active_request(client_id)
end

---@package
---@param client_id integer
function STHighlighter:debounce_request(client_id)
  local state = assert(self.client_state[client_id])
  self:reset_timer(state)
  if self.debounce > 0 then
    state.timer = vim.defer_fn(function()
      self:send_request(client_id)
    end, self.debounce)
  else
    self:send_request(client_id)
  end
end

---@private
---@param state STClientState
function STHighlighter:reset_timer(state)
  local timer = state.timer
  if timer then
    state.timer = nil
    if not timer:is_closing() then
      timer:stop()
      timer:close()
    end
  end
end

--- Start the semantic token highlighting engine for the given buffer with the
--- given client. The client must already be attached to the buffer.
---
--- NOTE: This is currently called automatically by |vim.lsp.buf_attach_client()|. To
--- opt-out of semantic highlighting with a server that supports it, you can
--- delete the semanticTokensProvider table from the {server_capabilities} of
--- your client in your |LspAttach| callback or your configuration's
--- `on_attach` callback:
---
--- ```lua
--- client.server_capabilities.semanticTokensProvider = nil
--- ```
---
---@deprecated
---@param bufnr (integer) Buffer number, or `0` for current buffer
---@param client_id (integer) The ID of the |vim.lsp.Client|
---@param opts? (table) Optional keyword arguments
---  - debounce (integer, default: 200): Debounce token requests
---        to the server by the given number in milliseconds
function M.start(bufnr, client_id, opts)
  vim.deprecate('vim.lsp.semantic_tokens.start', 'vim.lsp.semantic_tokens.enable(true)', '0.13.0')
  vim.validate('bufnr', bufnr, 'number')
  vim.validate('client_id', client_id, 'number')

  M.enable(true, { bufnr = bufnr, client_id = client_id })

  if opts and opts.debounce and STHighlighter.active[bufnr] then
    local highlighter = STHighlighter.active[bufnr]
    local prev = rawget(highlighter, 'debounce')
    highlighter.debounce = prev and math.max(prev, opts.debounce) or opts.debounce
  end
end

--- Stop the semantic token highlighting engine for the given buffer with the
--- given client.
---
---@deprecated
---@param bufnr (integer) Buffer number, or `0` for current buffer
---@param client_id (integer) The ID of the |vim.lsp.Client|
function M.stop(bufnr, client_id)
  vim.deprecate('vim.lsp.semantic_tokens.stop', 'vim.lsp.semantic_tokens.enable(false)', '0.13.0')
  M.enable(false, { bufnr = bufnr, client_id = client_id })
end

--- Query whether semantic tokens is enabled in the {filter}ed scope
---@param filter? vim.lsp.capability.enable.Filter
function M.is_enabled(filter)
  return vim.lsp._capability.is_enabled('semantic_tokens', filter)
end

--- Enables or disables semantic tokens for the {filter}ed scope.
---
--- To "toggle", pass the inverse of `is_enabled()`:
---
--- ```lua
--- vim.lsp.semantic_tokens.enable(not vim.lsp.semantic_tokens.is_enabled())
--- ```
---
---@param enable? boolean true/nil to enable, false to disable
---@param filter? vim.lsp.capability.enable.Filter
function M.enable(enable, filter)
  vim.lsp._capability.enable('semantic_tokens', enable, filter)
end

--- @nodoc
--- @class STTokenRangeInspect : STTokenRange
--- @field client_id integer

--- Return the semantic token(s) at the given position.
--- If called without arguments, returns the token under the cursor.
---
---@param bufnr integer|nil Buffer number (0 for current buffer, default)
---@param row integer|nil Position row (default cursor position)
---@param col integer|nil Position column (default cursor position)
---
---@return STTokenRangeInspect[]|nil (table|nil) List of tokens at position. Each token has
---        the following fields:
---        - line (integer) line number, 0-based
---        - start_col (integer) start column, 0-based
---        - end_line (integer) end line number, 0-based
---        - end_col (integer) end column, 0-based
---        - type (string) token type as string, e.g. "variable"
---        - modifiers (table) token modifiers as a set. E.g., { static = true, readonly = true }
---        - client_id (integer)
function M.get_at_pos(bufnr, row, col)
  bufnr = vim._resolve_bufnr(bufnr)

  local highlighter = STHighlighter.active[bufnr]
  if not highlighter then
    return
  end

  if row == nil or col == nil then
    local cursor = api.nvim_win_get_cursor(0)
    row, col = cursor[1] - 1, cursor[2]
  end

  local position = { row, col, row, col }

  local tokens = {} --- @type STTokenRangeInspect[]
  for client_id, client in pairs(highlighter.client_state) do
    local highlights = client.current_result.highlights
    if highlights then
      local idx = vim.list.bisect(highlights, { end_line = row }, {
        key = function(highlight)
          return highlight.end_line
        end,
      })
      for i = idx, #highlights do
        local token = highlights[i]
        --- @cast token STTokenRangeInspect

        if token.line > row then
          break
        end

        if
          Range.contains({ token.line, token.start_col, token.end_line, token.end_col }, position)
        then
          token.client_id = client_id
          tokens[#tokens + 1] = token
        end
      end
    end
  end
  return tokens
end

--- Force a refresh of all semantic tokens
---
--- Only has an effect if the buffer is currently active for semantic token
--- highlighting (|vim.lsp.semantic_tokens.enable()| has been called for it)
---
---@param bufnr (integer|nil) filter by buffer. All buffers if nil, current
---       buffer if 0
function M.force_refresh(bufnr)
  vim.validate('bufnr', bufnr, 'number', true)

  local buffers = bufnr == nil and vim.tbl_keys(STHighlighter.active)
    or { vim._resolve_bufnr(bufnr) }

  for _, buffer in ipairs(buffers) do
    local highlighter = STHighlighter.active[buffer]
    if highlighter then
      for client_id, _ in pairs(highlighter.client_state) do
        highlighter:reset(client_id)
        highlighter:send_request(client_id)
      end
    end
  end
end

--- @class vim.lsp.semantic_tokens.highlight_token.Opts
--- @inlinedoc
---
--- Priority for the applied extmark.
--- (Default: `vim.hl.priorities.semantic_tokens + 3`)
--- @field priority? integer

--- Highlight a semantic token.
---
--- Apply an extmark with a given highlight group for a semantic token. The
--- mark will be deleted by the semantic token engine when appropriate; for
--- example, when the LSP sends updated tokens. This function is intended for
--- use inside |LspTokenUpdate| callbacks.
---@param token (table) Semantic token, provided as `ev.data.token` in |LspTokenUpdate|
---@param bufnr (integer) Buffer to highlight, or `0` for current buffer.
---@param client_id (integer) ID of the |vim.lsp.Client|
---@param hl_group (string) Highlight group name
---@param opts? vim.lsp.semantic_tokens.highlight_token.Opts  Optional parameters:
function M.highlight_token(token, bufnr, client_id, hl_group, opts)
  bufnr = vim._resolve_bufnr(bufnr)
  local highlighter = STHighlighter.active[bufnr]
  if not highlighter then
    return
  end

  local state = highlighter.client_state[client_id]
  if not state then
    return
  end

  local priority = opts and opts.priority or vim.hl.priorities.semantic_tokens + 3

  set_mark(bufnr, state.namespace, token, hl_group, priority)
end

--- |lsp-handler| for the method `workspace/semanticTokens/refresh`
---
--- Refresh requests are sent by the server to indicate a project-wide change
--- that requires all tokens to be re-requested by the client. This handler will
--- invalidate the current results of all buffers and automatically kick off a
--- new request for buffers that are displayed in a window. For those that aren't,
--- the BufWinEnter event should take care of it next time it's displayed.
---@param ctx lsp.HandlerContext
function M._refresh(err, _, ctx)
  if err then
    return vim.NIL
  end

  for bufnr, highlighter in pairs(STHighlighter.active) do
    if highlighter.client_state[ctx.client_id] then
      highlighter:mark_dirty(ctx.client_id)

      if not vim.tbl_isempty(vim.fn.win_findbuf(bufnr)) then
        -- some LSPs send rapid fire refresh notifications, so we'll debounce them with debounce_request()
        highlighter:debounce_request(ctx.client_id)
      end
    end
  end

  return vim.NIL
end

local namespace = api.nvim_create_namespace('nvim.lsp.semantic_tokens')
api.nvim_set_decoration_provider(namespace, {
  on_win = function(_, _, bufnr, topline, botline)
    local highlighter = STHighlighter.active[bufnr]
    if highlighter then
      highlighter:on_win(topline, botline)
    end
  end,
})

-- Semantic tokens is enabled by default
M.enable(true)

--- for testing only! there is no guarantee of API stability with this!
---
---@private
M.__STHighlighter = STHighlighter

return M
