From 71fa9d4e93dda17fc66dbeed4d5c9c6e3fa6b7c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Javier=20L=C3=B3pez?= <graulopezjavier@gmail.com>
Date: Sat, 4 Dec 2021 11:27:36 -0500
Subject: [PATCH] refactor(help): move it to Lua

---
 runtime/lua/vim/help.lua | 201 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 201 insertions(+)
 create mode 100644 runtime/lua/vim/help.lua

diff --git a/runtime/lua/vim/help.lua b/runtime/lua/vim/help.lua
new file mode 100644
index 0000000000..41dc2d13a3
--- /dev/null
+++ b/runtime/lua/vim/help.lua
@@ -0,0 +1,201 @@
+local M = {}
+local vim = vim
+local nvim_get_runtime_file = vim.api.nvim_get_runtime_file
+
+---Find the tagfiles to search tags on.
+---Tag falenames have the pattern 'tags(-\w\w)?' :help :helptags
+---@param lang string|nil The tagname to search for.
+M.tag_files_search = function(lang)
+  local patt = "doc/tags"
+  local res = {}
+  if lang ~= nil then
+    patt = string.format("%s-%s", patt, lang)
+  end
+  res = nvim_get_runtime_file(patt, true)
+  return res
+end
+
+---Find the tags that match the given pattern in the given language.
+M.find_tags = function(patterns, lang)
+  local files = M.tag_files_search(lang)
+  -- Matches will be stored here by find_in_tagfile_and_score
+  local results = { count = 0, matches = {} }
+  for _, fname in ipairs(files) do
+    -- Finds the tags in each file, scores them and adds them to the results
+    M.find_in_tagfile_and_score(fname, results, patterns)
+  end
+  return results
+end
+
+---A tagfile is a tab separated file with three fields: tagname, file, tag_regexp
+---This function finds the tags that mtch the given patterns and scores the match. The results are
+---appened to the results.matches table.
+---@param filename string the full path of the tagfile to search in.
+---@param results table with two keys count number, matches table
+---@param patterns table with keys escaped, icase, wildcard
+---@return nil
+M.find_in_tagfile_and_score = function(filename, results, patterns)
+  -- TODO: Do you even vim.loop
+  local file = io.open(filename, "r")
+  local contents = file:read("*a")
+  file:close()
+  local escaped, icase, wildcard = patterns.escaped, patterns.icase, patterns.wildcard
+  local score, entry, tag, add = 0, {}, "", false
+  local matchpos, t
+  for line in vim.gsplit(contents, '\n', true) do
+    if line == "" then break end
+    entry = vim.split(line, "\t")
+    tag = entry[1]
+    matchpos = tag:find(escaped)
+    -- Regular case sensitive escaped pattern match
+    if matchpos ~= nil then
+      add = true
+      t = 'pattern'
+    else
+      -- Case insensitive match
+      matchpos = tag:find(icase)
+      if matchpos ~= nil then
+        add = true
+        -- Add 5000 if the match is case insensitive
+        score = score + 5000
+        t = 'icase'
+      else
+        -- Wildcard match
+        matchpos = tag:find(wildcard)
+        if matchpos ~= nil then
+          add = true
+          -- Add 20000 if it was a wildcard match
+          score = score + 20000
+        end
+      end
+    end
+    if add then
+      -- Add the number of chars/length of tag
+      score = score + #tag
+      -- Add 100 for every letter of the match
+      tag:gsub("%a", function()
+        score = score + 100
+      end)
+      -- Add 10000 when the match is not at the start but making sure matchpos and matchpos-1 are
+      -- alphanumeir
+      if matchpos > 1 and string.find(tag, '^%w%w', matchpos - 1, false) then
+        score = score + 10000
+      -- If it's over the third position mulyiply by 200
+      else if matchpos > 3 then
+        score = score * 200
+      end
+      end
+      results.count = results.count + 1
+      results.matches[results.count] = { entry[1], filename:gsub('tags.-$', entry[2]), entry[3], score, t}
+    end
+    add = false
+    score = 0
+  end
+end
+
+---Patterns in which the whole match is replaced
+local full_replacements = {
+  ["*"] = "star",
+  ["g*"] = "gstar",
+  ["[*"] = "[star",
+  ["]*"] = "]star",
+  ["/*"] = "/star",
+  ["/\\*"] = "/\\star",
+  ['"*'] = "quotestar",
+  ["**"] = "starstar",
+}
+
+---Search for the following patterns in the tag name and replace them.
+---Items: { pattern, replacement, should_escape_pattern }
+local replacements = {
+  ---NOTE: the order matters
+  { '"', "quote", true }, -- Replace " with quote
+  { "|", "bar", true }, -- Repce | with bar
+  -- The next two need to be applied in order one expands ^ the other separates repetitive
+  { "%^(.)", "CTRL%-%1", false }, -- ^n to CTRL-n
+  { "(CTRL%-.)([^_])", "%1_%2", false }, -- Insert _ between CTRL-x_CTRL-n
+}
+
+---Make lua pattern case insensitive.
+---@param text string the text/pattern to make case insensitive.
+---@return string The case insensitive pattern.
+local function ignorecase_pattern(text)
+  return text:gsub("(%a)", function(a)
+    return string.format("[%s%s]", a:lower(), a:upper())
+  end)
+end
+
+---Escape any lua pattern matching characters.
+---@param text string The text/pattern to escape.
+local function escape_pattern(text)
+  return text:gsub("([^%w])", "%%%1")
+end
+
+---Given user input transform it to be a tagname, and return the lua patterns to search.
+---Three patterns are necessary: normal, case insensitive, and wildcards enabled '*' or '?'.
+---@param name string user input that represents a tagname.
+---@return string, string first pattern is with all magic chatacters escaped, second is with wildcards enabled.
+M.generate_search_patterns = function(name)
+  -- The escaping of the returned tag name is only escaped once at the time of return
+  if full_replacements[name] ~= nil then
+    name = full_replacements[name]
+  else
+    -- Perform the replacements
+    local patt, repl, should_escape
+    for _, expr in ipairs(replacements) do
+      patt, repl, should_escape = expr[1], expr[2], expr[3]
+      if should_escape then
+        patt = escape_pattern(patt)
+      end
+      name = name:gsub(patt, repl)
+    end
+  end
+  -- Escaped pattern assures the tag is looked by the name without the characters having any
+  -- special meaning
+  local patterns = {}
+  patterns.escaped = escape_pattern(name)
+  patterns.icase = ignorecase_pattern(patterns.escaped)
+  patterns.wildcard = patterns.escaped:gsub("%%%*", ".*"):gsub("%%%?", ".")
+  if patterns.escaped == patterns.wildcard then
+    patterns.wildcard ='^$'
+  end
+  return patterns
+end
+
+M.ex_help = function(tag_name)
+  local patterns = M.generate_search_patterns(tag_name)
+  print("Generated patterns", vim.inspect(patterns))
+  local results = M.find_tags(patterns, nil)
+  table.sort(results.matches, function(a, b)
+    return a[4] < b[4]
+  end)
+  print(vim.inspect(results))
+end
+
+-- Examples
+-- M.ex_help([[CTRL-\_CTRL-N]])
+-- M.ex_help([[^N]])
+-- M.ex_help([[i_^_]])
+-- M.ex_help([[i_^_^D]]) -- Special case doesn't work and I think it shouldn't
+-- M.ex_help([[^_]])
+-- M.ex_help([[/|]])
+-- M.ex_help([[i_^x^E]])
+-- M.ex_help([[^X^N]])
+-- M.ex_help([[^x^N]])
+-- M.ex_help([[Cino]])
+-- M.ex_help([[sort]])
+-- M.ex_help("[pattern]")
+-- M.ex_help("s/\\1")
+-- M.ex_help([[/\star]])
+-- M.ex_help(":s\\=")
+-- M.ex_help([['sp]])
+-- M.ex_help([[motion]])
+-- M.ex_help([[expr-!~]])
+-- M.ex_help([[rw?]])
+-- M.ex_help([[netrw-%]])
+-- M.ex_help([[...]])
+-- M.ex_help([[tw?]])
+M.ex_help([[c*vis]])
+-- M.ex_help([[z?]])
+
+return M