#!/usr/bin/env -S nvim -l
local root = vim.trim(vim.system({ 'git', 'rev-parse', '--show-toplevel' }):wait().stdout)
vim.opt.rtp:append(root)

local util = require 'lspconfig.util'
local inspect = vim.inspect

local function template(s, params)
  return (s:gsub('{{([^{}]+)}}', params))
end

local function map_list(t, func)
  local res = {}
  for i, v in ipairs(t) do
    local x = func(v, i)
    if x ~= nil then
      table.insert(res, x)
    end
  end
  return res
end

local function map_sorted(t, func)
  local res = {}
  for k, v in vim.spairs(t) do
    local x = func(k, v)
    if x ~= nil then
      table.insert(res, x)
    end
  end
  return res
end

local function indent(n, s)
  local prefix = string.rep(' ', n)
  return s:gsub('([^\n]+)', prefix .. '%1')
end

local function make_parts(fns)
  return util.tbl_flatten(map_list(fns, function(v)
    if type(v) == 'function' then
      v = v()
    end
    return { v }
  end))
end

local function make_section(indentlvl, sep, parts)
  local flat = make_parts(parts)
  if not flat or #flat == 0 then
    return ''
  end
  return indent(indentlvl, table.concat(flat, sep))
end

local function readfile(path)
  assert((vim.uv.fs_stat(path) or {}).type == 'file')
  return io.open(path):read '*a'
end

local section_template_txt = [[
------------------------------------------------------------------------------
{{config_name}}

{{preamble}}

Snippet to enable the language server: >lua
  vim.lsp.enable('{{config_name}}')

{{commands}}
Default config:
{{default_values}}

]]

local section_template_md = [[
## {{config_name}}

{{preamble}}

Snippet to enable the language server:
```lua
require'lspconfig'.{{config_name}}.setup{}
```
{{commands}}
Default config:
{{default_values}}

---
]]

--- Gets docstring by looking for "@brief" in a Lua code docstring.
local function extract_brief(text)
  local doc = text:match('%-%-+ *%@brief.-(\n%-%-.*)')
  if not doc then
    return ''
  end
  -- Remove all lines following the last comment ("-- …").
  doc = doc:match('(.-)\n[^-]+')
  -- Remove "--" prefix from all lines.
  doc = doc:gsub('\n%-%-+', '\n')
  -- Remove leading whitespace (shared indent).
  doc = vim.trim(vim.text.indent(0, doc))
  return doc
end

local function make_lsp_sections(is_markdown)
  local lsp_files = vim.fs.find(function(f)
    return f:match('.*%.lua$')
  end, { type = 'file', path = vim.fs.joinpath(root, 'lsp'), limit = math.huge })
  local config_sections = {}

  for _, config_file in ipairs(lsp_files) do
    -- "lua/xx.lua"
    local config_name = config_file:match('lsp/(.-)%.lua$')
    if config_name then
      local config = require('lsp.' .. config_name)
      local docstring = extract_brief(readfile(config_file))
      local params = {
        config_name = config_name,
        preamble = docstring,
        commands = '',
        default_values = '',
      }

      -- TODO: get commands by parsing `nvim_buf_create_user_command` calls.
      params.commands = make_section(0, '\n', {
        function()
          if not config.commands or #vim.tbl_keys(config.commands) == 0 then
            return
          end
          return ('\nCommands:\n%s\n'):format(make_section(0, '\n', {
            map_sorted(config.commands, function(name, def)
              if def.description then
                return string.format('- %s: %s', name, def.description)
              end
              return string.format('- %s', name)
            end),
          }))
        end,
      })

      params.default_values = make_section(0, '\n', {
        function()
          return make_section(0, '\n', {
            map_sorted(config, function(k, v)
              if type(v) == 'boolean' then
                return ('- `%s` : `%s`'):format(k, v)
              elseif type(v) ~= 'function' and k ~= 'root_dir' then
                return ('- `%s` :\n  ```lua\n%s\n  ```'):format(k, indent(2, inspect(v)))
              end

              local file = assert(io.open(config_file, 'r'))
              local linenr = 0
              -- Find the `return` line, where the config starts.
              for line in file:lines() do
                linenr = linenr + 1
                if line:find('^return') then
                  break
                end
              end
              io.close(file)
              local config_relpath = vim.fs.relpath(root, config_file)

              -- XXX: "../" because the path is outside of the doc/ dir.
              return ('- `%s` source (use "gF" to open): [../%s:%d](../%s#L%d)'):format(
                k,
                config_relpath,
                linenr,
                config_relpath,
                linenr
              )
            end),
          })
        end,
      })

      local template_used = is_markdown and section_template_md or section_template_txt
      table.insert(config_sections, template(template_used, params))
    end
  end

  return make_section(0, '\n', config_sections)
end

--- Gets the list of config names and returns "table of contents" as markdown.
local function make_toc()
  local lsp_files = vim.fs.find(function(f)
    return f:match('.*%.lua$')
  end, { type = 'file', path = vim.fs.joinpath(root, 'lsp'), limit = math.huge })
  local server_list = {}

  for _, file_path in ipairs(lsp_files) do
    local config_name = file_path:match('lsp/(.-)%.lua$')
    if config_name then
      table.insert(server_list, template('- [{{server}}](#{{server}})', { server = config_name }))
    end
  end

  return make_section(0, '\n', server_list)
end

local function generate_readme(template_file, params, output_file)
  local input_template = readfile(template_file)
  local readme_data = template(input_template, params)

  local writer = assert(io.open(output_file, 'w'))
  writer:write(readme_data)
  writer:close()
end

generate_readme(vim.fs.joinpath(root, 'scripts/docs_template.md'), {
  toc = make_toc(),
  lsp_server_details = make_lsp_sections(true),
}, vim.fs.joinpath(root, 'doc/configs.md'))

generate_readme(vim.fs.joinpath(root, 'scripts/docs_template.txt'), {
  toc = make_toc(),
  lsp_server_details = make_lsp_sections(false),
}, vim.fs.joinpath(root, 'doc/configs.txt'))