feat: enable prompt caching for the Anthropic API

lua/avante/tiktoken.lua

@@ -0,0 +1,103 @@
+-- NOTE: this file is copied from: https://github.com/CopilotC-Nvim/CopilotChat.nvim/blob/canary/lua/CopilotChat/tiktoken.lua
+
+local curl = require("plenary.curl")
+local tiktoken_core = nil
+
+---Get the path of the cache directory
+---@param fname string
+---@return string
+local function get_cache_path(fname)
+  return vim.fn.stdpath("cache") .. "/" .. fname
+end
+
+local function file_exists(name)
+  local f = io.open(name, "r")
+  if f ~= nil then
+    io.close(f)
+    return true
+  else
+    return false
+  end
+end
+
+--- Load tiktoken data from cache or download it
+local function load_tiktoken_data(done, model)
+  local tiktoken_url = "https://openaipublic.blob.core.windows.net/encodings/cl100k_base.tiktoken"
+  -- If model is gpt-4o, use o200k_base.tiktoken
+  if model ~= nil and vim.startswith(model, "gpt-4o") then
+    tiktoken_url = "https://openaipublic.blob.core.windows.net/encodings/o200k_base.tiktoken"
+  end
+  local async
+  async = vim.loop.new_async(function()
+    -- Take filename after the last slash of the url
+    local cache_path = get_cache_path(tiktoken_url:match(".+/(.+)"))
+    if not file_exists(cache_path) then
+      vim.schedule(function()
+        curl.get(tiktoken_url, {
+          output = cache_path,
+        })
+        done(cache_path)
+      end)
+    else
+      done(cache_path)
+    end
+    async:close()
+  end)
+  async:send()
+end
+
+local M = {}
+
+---@param model string|nil
+function M.setup(model)
+  local ok, core = pcall(require, "tiktoken_core")
+  if not ok then
+    print("Warn: tiktoken_core is not found!!!!")
+    return
+  end
+
+  load_tiktoken_data(function(path)
+    local special_tokens = {}
+    special_tokens["<|endoftext|>"] = 100257
+    special_tokens["<|fim_prefix|>"] = 100258
+    special_tokens["<|fim_middle|>"] = 100259
+    special_tokens["<|fim_suffix|>"] = 100260
+    special_tokens["<|endofprompt|>"] = 100276
+    local pat_str =
+      "(?i:'s|'t|'re|'ve|'m|'ll|'d)|[^\\r\\n\\p{L}\\p{N}]?\\p{L}+|\\p{N}{1,3}| ?[^\\s\\p{L}\\p{N}]+[\\r\\n]*|\\s*[\\r\\n]+|\\s+(?!\\S)|\\s+"
+    core.new(path, special_tokens, pat_str)
+    tiktoken_core = core
+  end, model)
+end
+
+function M.available()
+  return tiktoken_core ~= nil
+end
+
+function M.encode(prompt)
+  if not tiktoken_core then
+    return nil
+  end
+  if not prompt or prompt == "" then
+    return nil
+  end
+  -- Check if prompt is a string
+  if type(prompt) ~= "string" then
+    error("Prompt must be a string")
+  end
+  return tiktoken_core.encode(prompt)
+end
+
+function M.count(prompt)
+  if not tiktoken_core then
+    return math.ceil(#prompt * 0.2) -- Fallback to 0.2 character count
+  end
+
+  local tokens = M.encode(prompt)
+  if not tokens then
+    return 0
+  end
+  return #tokens
+end
+
+return M