--  Updates version.c list of applied Vim patches.
--
--  Usage:
--    VIM_SOURCE_DIR=~/neovim/.vim-src/ nvim -l ./scripts/vimpatch.lua

local nvim = vim.api

local function systemlist(...)
  local rv = nvim.nvim_call_function('systemlist', ...)
  local err = nvim.nvim_get_vvar('shell_error')
  local args_str = nvim.nvim_call_function('string', ...)
  if 0 ~= err then
    error('command failed: ' .. args_str)
  end
  return rv
end

local function vimpatch_sh_list_tokens()
  return systemlist({ { 'bash', '-c', 'scripts/vim-patch.sh -M' } })
end

-- Generate the data,lines to update src/nvim/version.c.
-- - `vim_versions[]`
-- - `Versions[]`
-- - `num_patches[]`
-- - `included_patchsets[]`
local function gen_version_c_lines()
  -- List of version sets where each set contains:
  -- 1. major_minor_version (int)
  -- 2. major_minor_version (string)
  -- 3. set of merged patch numbers
  local merged_version_list = {}
  for _, token in ipairs(vimpatch_sh_list_tokens()) do
    local major_version, minor_version, patch_num = string.match(token, '^(%d+).(%d+).(%d+)$')
    local n = tonumber(patch_num)
    if n then
      local major_minor_version = major_version * 100 + minor_version
      local len = #merged_version_list
      if len == 0 or merged_version_list[len][1] ~= major_minor_version then
        local vstr = '"' .. major_version .. '.' .. minor_version .. '"'
        table.insert(merged_version_list, { major_minor_version, vstr, { n } })
      else
        table.insert(merged_version_list[len][3], n)
      end
    end
  end

  local major_vim_versions = {}
  local major_vim_versions_str = {}
  local num_patches = {}
  local patch_lines = {}
  for _, version_set in ipairs(merged_version_list) do
    local major_minor_version, major_minor_version_str, patch_set = unpack(version_set)
    table.insert(major_vim_versions, major_minor_version)
    table.insert(major_vim_versions_str, major_minor_version_str)
    table.insert(num_patches, #patch_set)
    table.insert(patch_lines, '  (const int[]) {  // ' .. major_minor_version)

    local patchset_set = {}
    for i = #patch_set, 1, -1 do
      local patch = patch_set[i]
      local next_patch = patch_set[i - 1]
      local patch_diff = patch - (next_patch or 0)
      table.insert(patchset_set, patch)

      -- guard against last patch or `make formatc`
      if #patchset_set > 15 or i == 1 or patch_diff > 1 then
        table.insert(patch_lines, '    ' .. table.concat(patchset_set, ', ') .. ',')
        patchset_set = {}
      end
      if i == 1 and patch > 0 then
        local line = '    // 0'
        if patch > 1 then
          line = line .. '-' .. (patch - 1)
        end
        table.insert(patch_lines, line)
      elseif patch_diff > 1 then
        local line = '    // ' .. (next_patch + 1)
        if patch_diff > 2 then
          line = line .. '-' .. (patch - 1)
        end
        table.insert(patch_lines, line)
      end
    end

    table.insert(patch_lines, '  },')
  end

  return major_vim_versions, major_vim_versions_str, num_patches, patch_lines
end

local function patch_version_c()
  local major_vim_versions, major_vim_versions_str, num_patches, patch_lines = gen_version_c_lines()

  nvim.nvim_command('silent noswapfile noautocmd edit src/nvim/version.c')
  nvim.nvim_command([[/^char \*Versions]])
  -- Replace the line.
  nvim.nvim_call_function('setline', {
    nvim.nvim_eval('line(".")'),
    'char *Versions[] = { ' .. table.concat(major_vim_versions_str, ', ') .. ' };',
  })
  nvim.nvim_command([[/^static const int vim_versions]])
  -- Replace the line.
  nvim.nvim_call_function('setline', {
    nvim.nvim_eval('line(".")'),
    'static const int vim_versions[] = { ' .. table.concat(major_vim_versions, ', ') .. ' };',
  })
  nvim.nvim_command([[/^static const int num_patches]])
  -- Replace the line.
  nvim.nvim_call_function('setline', {
    nvim.nvim_eval('line(".")'),
    'static const int num_patches[] = { ' .. table.concat(num_patches, ', ') .. ' };',
  })
  nvim.nvim_command([[/^static const int \*included_patchsets]])
  -- Delete the existing lines.
  nvim.nvim_command('silent normal! j0d/};\rk')
  -- Insert the lines.
  nvim.nvim_call_function('append', {
    nvim.nvim_eval('line(".")'),
    patch_lines,
  })
  nvim.nvim_command('silent write')
end

patch_version_c()