local utils = require('CopilotChat.utils')
local class = utils.class

---@class CopilotChat.ui.Overlay : Class
---@field name string
---@field help string
---@field help_ns number
---@field on_buf_create fun(bufnr: number)
---@field bufnr number?
local Overlay = class(function(self, name, help, on_buf_create)
  self.name = name
  self.help = help
  self.help_ns = vim.api.nvim_create_namespace('copilot-chat-help')
  self.on_buf_create = on_buf_create
  self.bufnr = nil
end)

---@return number
function Overlay:create()
  local bufnr = vim.api.nvim_create_buf(false, true)
  vim.bo[bufnr].filetype = self.name
  vim.bo[bufnr].modifiable = false
  vim.api.nvim_buf_set_name(bufnr, self.name)
  return bufnr
end

---@return boolean
function Overlay:valid()
  return utils.buf_valid(self.bufnr)
end

function Overlay:validate()
  if self:valid() then
    return
  end

  self.bufnr = self:create()
  if self.on_buf_create then
    self.on_buf_create(self.bufnr)
  end
end

---@param text string
---@param winnr number
---@param filetype? string
---@param syntax string?
function Overlay:show(text, winnr, filetype, syntax)
  if not text or vim.trim(text) == '' then
    return
  end

  self:validate()
  text = text .. '\n'

  vim.api.nvim_win_set_buf(winnr, self.bufnr)
  vim.bo[self.bufnr].modifiable = true
  vim.api.nvim_buf_set_lines(self.bufnr, 0, -1, false, vim.split(text, '\n'))
  vim.bo[self.bufnr].modifiable = false
  self:show_help(self.help, -1)
  vim.api.nvim_win_set_cursor(winnr, { vim.api.nvim_buf_line_count(self.bufnr), 0 })

  filetype = filetype or 'text'
  syntax = syntax or filetype

  -- Dual mode with treesitter (for diffs for example)
  local ok, parser = pcall(vim.treesitter.get_parser, self.bufnr, syntax)
  if ok and parser then
    vim.treesitter.start(self.bufnr, syntax)
    vim.bo[self.bufnr].syntax = filetype
  else
    vim.bo[self.bufnr].syntax = syntax
  end
end

---@param winnr number
---@param bufnr number?
function Overlay:restore(winnr, bufnr)
  vim.api.nvim_win_set_buf(winnr, bufnr or 0)
end

function Overlay:delete()
  if self:valid() then
    vim.api.nvim_buf_delete(self.bufnr, { force = true })
  end
end

---@param msg string
---@param offset number
function Overlay:show_help(msg, offset)
  if not msg then
    return
  end

  msg = vim.trim(msg)
  if msg == '' then
    return
  end

  self:validate()
  local line = vim.api.nvim_buf_line_count(self.bufnr) + offset
  vim.api.nvim_buf_set_extmark(self.bufnr, self.help_ns, math.max(0, line - 1), 0, {
    id = 1,
    hl_mode = 'combine',
    priority = 100,
    virt_lines = vim.tbl_map(function(t)
      return { { t, 'CopilotChatHelp' } }
    end, vim.split(msg, '\n')),
  })
end

function Overlay:clear_help()
  vim.api.nvim_buf_del_extmark(self.bufnr, self.help_ns, 1)
end

return Overlay