local serpent = require 'serpent'

-- Helpers

local function copy(t)
  if type(t) ~= 'table' then return t end
  local result = {}
  for k, v in pairs(t) do
    result[k] = copy(v)
  end
  return result
end

local function unindent(code)
  local indent = code:match('^(% +)')
  if indent then
    return code:gsub('\n' .. indent, '\n'):gsub('^' .. indent, ''):gsub('%s*$', '')
  else
    return code
  end
end

local function unwrap(str)
  if not str then return str end
  str = unindent(str)
  return str:gsub('([^\n])\n(%S)', function(a, b)
    if b == '-' or b == '>' then
      return a .. '\n' .. b
    else
      return a .. ' ' .. b
    end
  end)
    :gsub('^%s+', '')
    :gsub('%s+$', '')
end

local function pluralify(t, key)
  t[key .. 's'] = t[key .. 's'] or (t[key] and { t[key] } or nil)
  t[key] = nil
  return t[key .. 's']
end

local lookup = {}
local function track(obj)
  lookup[obj.key] = obj
end

local function warnIf(cond, s, ...)
  if cond then print(string.format(s, ...)) end
end

-- Objects that are lowercase need to be special-cased
local objectSnowflakes = { vec3 = true, quat = true, mat4 = true }

-- Processors
local function processExample(example)
  if type(example) == 'string' then
    return {
      code = unindent(example)
    }
  else
    example.description = unwrap(example.description)
    example.code = unindent(example.code)
  end

  return example
end

local function processEnum(path, parent)
  local enum = require(path)

  enum.name = path:match('[^/]+$')
  enum.key = enum.name
  enum.module = parent.key
  enum.description = unwrap(enum.description)
  enum.notes = unwrap(enum.notes)

  for _, value in ipairs(enum.values) do
    value.description = unwrap(value.description)
  end

  track(enum)
  return enum
end

local function processFunction(path, parent)
  local fn = require(path)

  local isMethod = parent.name:match('^[A-Z]') or objectSnowflakes[parent.key]

  fn.name = path:match('[^/]+$')
  fn.key = isMethod and (parent.key .. ':' .. fn.name) or (path:gsub('/', '.'):gsub('callbacks%.', ''))
  fn.description = unwrap(fn.description)
  fn.module = parent.module or parent.key
  fn.notes = unwrap(fn.notes)
  fn.examples = pluralify(fn, 'example')

  for k, example in ipairs(fn.examples or {}) do
    fn.examples[k] = processExample(example)
  end

  if not fn.variants then
    fn.variants = {
      {
        arguments = fn.arguments,
        returns = fn.returns
      }
    }
  else
    for name, arg in pairs(fn.arguments) do
      arg.name = name
    end

    for name, ret in pairs(fn.returns) do
      ret.name = name
    end

    for _, variant in ipairs(fn.variants) do
      for i, name in ipairs(variant.arguments) do
        variant.arguments[i] = copy(fn.arguments[name])
      end

      for i, name in ipairs(variant.returns) do
        variant.returns[i] = copy(fn.returns[name])
      end
    end
  end

  for _, variant in ipairs(fn.variants) do
    local function processTable(t)
      if not t then return end

      for _, field in ipairs(t) do
        field.description = unwrap(field.description)
        processTable(field.table)
      end

      t.description = unwrap(t.description)
    end

    variant.description = unwrap(variant.description)

    for _, arg in ipairs(variant.arguments) do
      arg.description = unwrap(arg.description)
      processTable(arg.table)
    end

    for _, ret in ipairs(variant.returns) do
      ret.description = unwrap(ret.description)
      processTable(ret.table)
    end
  end

  fn.arguments = nil
  fn.returns = nil

  track(fn)
  return fn
end

local function processObject(path, parent)
  local object = require(path .. '.init')

  object.key = path:match('[^/]+$')
  object.name = object.key
  object.description = unwrap(object.description)
  object.summary = object.summary or object.description
  object.module = parent.key
  object.methods = {}
  object.constructors = pluralify(object, 'constructor')
  object.notes = unwrap(object.notes)
  object.examples = pluralify(object, 'example')

  if object.sections then
    for _, section in ipairs(object.sections) do
      section.description = unwrap(section.description)
    end
  end

  for k, example in ipairs(object.examples or {}) do
    object.examples[k] = processExample(example)
  end

  for _, file in ipairs(lovr.filesystem.getDirectoryItems(path)) do
    if file ~= 'init.lua' then
      table.insert(object.methods, processFunction(path .. '/' .. file:gsub('%..+$', ''), object))
    end
  end

  table.sort(object.methods, function(a, b) return a.key < b.key end)

  track(object)
  return object
end

local function processModule(path)
  local module = require(path .. '.init') -- So we avoid requiring the module itself

  module.key = module.external and path:match('[^/]+$') or path:gsub('/', '.')
  module.name = module.external and module.key or module.key:match('[^%.]+$')
  module.description = unwrap(module.description)
  module.functions = {}
  module.objects = {}
  module.enums = {}
  module.notes = unwrap(module.notes)

  if module.sections then
    for _, section in ipairs(module.sections) do
      section.description = unwrap(section.description)
    end
  end

  module.examples = pluralify(module, 'example')
  for k, example in ipairs(module.examples or {}) do
    module.examples[k] = processExample(example)
  end

  for _, file in ipairs(lovr.filesystem.getDirectoryItems(path)) do
    local childPath = path .. '/' .. file
    local childModule = childPath:gsub('%..+$', '')
    local isFile = lovr.filesystem.isFile(childPath)
    local capitalized = file:match('^[A-Z]')

    if file ~= 'init.lua' and not capitalized and isFile then
      table.insert(module.functions, processFunction(childModule, module))
    elseif capitalized and isFile then
      table.insert(module.enums, processEnum(childModule, module))
    elseif not isFile and (capitalized or objectSnowflakes[file]) then
      table.insert(module.objects, processObject(childModule, module))
    end
  end

  table.sort(module.functions, function(a, b) return a.key < b.key end)
  table.sort(module.objects, function(a, b) return a.key < b.key end)
  table.sort(module.enums, function(a, b) return a.key < b.key end)

  track(module)
  return module
end

-- Validation
local function validateRelated(item)
  for _, key in ipairs(item.related or {}) do
    warnIf(not lookup[key], 'Related item for %s not found: %s', item.key, key)
  end
end

local function validateEnum(enum)
  validateRelated(enum)
end

local function validateObject(object)
  for _, constructor in ipairs(object.constructors or {}) do
    warnIf(not lookup[constructor], 'Constructor for %s not found: %s', object.key, constructor)
  end

  validateRelated(object)
end

local function validateFunction(fn)
  if fn.tag then
    local found = false
    for _, section in ipairs(lookup[fn.module].sections or {}) do
      if section.tag == fn.tag then found = true break end
    end
    warnIf(not found, 'Unknown tag %s for %s', fn.tag, fn.key)
  end

  for _, variant in ipairs(fn.variants) do
    for _, arg in ipairs(variant.arguments) do
      warnIf(not arg or not arg.name, 'Invalid argument for variant of %s', fn.key)
    end

    for _, ret in ipairs(variant.returns) do
      warnIf(not ret or not ret.name, 'Invalid return for variant of %s', fn.key)
    end
  end

  validateRelated(fn)
end

local function validateModule(module)
  for _, object in ipairs(module.objects) do
    validateObject(object)
  end

  for _, fn in ipairs(module.functions) do
    validateFunction(fn)
  end

  for _, fn in ipairs(module.enums) do
    validateEnum(fn)
  end
end

function lovr.load()
  local api = {
    modules = {},
    callbacks = {}
  }

  -- Modules
  table.insert(api.modules, processModule('lovr'))

  for _, file in ipairs(lovr.filesystem.getDirectoryItems('lovr')) do
    local path = 'lovr/' .. file

    if file ~= 'callbacks' and file:match('^[a-z]') and lovr.filesystem.isDirectory(path) then
      table.insert(api.modules, processModule(path))
    end
  end

  -- Callbacks
  local callbacks = 'lovr/callbacks'
  for _, file in ipairs(lovr.filesystem.getDirectoryItems(callbacks)) do
    table.insert(api.callbacks, processFunction(callbacks .. '/' .. file:gsub('%.lua', ''), api.modules[1]))
  end

  -- Validate
  for _, module in ipairs(api.modules) do
    validateModule(module)
  end

  -- Sort
  table.sort(api.modules, function(a, b) return a.key < b.key end)
  table.sort(api.callbacks, function(a, b) return a.key < b.key end)

  -- Serialize
  local file = io.open(lovr.filesystem.getSource() .. '/init.lua', 'w')
  assert(file, 'Could not open init.lua for writing')

  local keyPriority = {
    name = 1,
    tag = 2,
    summary = 3,
    type = 4,
    description = 5,
    key = 6,
    module = 7,
    arguments = 8,
    returns = 9
  }
  local function sort(keys, t)
    table.sort(keys, function(a, b) return (keyPriority[a] or 1000) < (keyPriority[b] or 1000) end)
  end
  local contents = 'return ' .. serpent.block(api, { comment = false, sortkeys = sort })
  file:write(contents)
  file:close()

  -- Bye
  lovr.event.quit()
end