local M = {}

local context = require('chatgpt_nvim.context')
local handler = require('chatgpt_nvim.handler')
local config = require('chatgpt_nvim.config')
local ui = require('chatgpt_nvim.ui')
local prompts = require('chatgpt_nvim.prompts')

local tools_manager = require("chatgpt_nvim.tools.manager")
local tools_module = require("chatgpt_nvim.tools")

local ok_yaml, lyaml = pcall(require, "lyaml")

------------------------------------------------------------------------------
-- UTILITIES
------------------------------------------------------------------------------
local function copy_to_clipboard(text)
  vim.fn.setreg('+', text)
end

local function parse_response(raw, conf)
  if not ok_yaml then
    vim.api.nvim_err_writeln("lyaml not available. Install with `luarocks install lyaml`.")
    return nil
  end
  local ok, data = pcall(lyaml.load, raw)
  if not ok or not data then
    vim.api.nvim_err_writeln("Failed to parse YAML response.")
    ui.debug_log("RAW response that failed parsing:\n" .. raw)
    return nil
  end
  ui.debug_log("Successfully parsed YAML response.")
  return data
end

local function is_subpath(root, path)
  local root_abs = vim.fn.fnamemodify(root, ":p")
  local target_abs = vim.fn.fnamemodify(path, ":p")
  return target_abs:sub(1, #root_abs) == root_abs
end

local function read_file(path)
  local fd = vim.loop.fs_open(path, "r", 438)
  if not fd then
    return nil
  end
  local stat = vim.loop.fs_fstat(fd)
  if not stat then
    vim.loop.fs_close(fd)
    return nil
  end
  local data = vim.loop.fs_read(fd, stat.size, 0)
  vim.loop.fs_close(fd)
  return data
end

local function close_existing_buffer_by_name(pattern)
  for _, b in ipairs(vim.api.nvim_list_bufs()) do
    local name = vim.api.nvim_buf_get_name(b)
    if name:match(pattern) then
      vim.api.nvim_buf_delete(b, { force = true })
    end
  end
end

------------------------------------------------------------------------------
-- PROMPT CONSTRUCTION
------------------------------------------------------------------------------
local function build_tools_available_block()
  local lines = {}
  lines[#lines+1] = "<tools_available>"
  for _, t in ipairs(tools_module.available_tools) do
    lines[#lines+1] = string.format("- **%s**: %s\n  Usage: %s",
      t.name, t.explanation, t.usage
    )
  end
  lines[#lines+1] = "</tools_available>"
  return table.concat(lines, "\n")
end

local function build_prompt(user_input, dirs, conf)
  local root = vim.fn.getcwd()
  local initial_files = conf.initial_files or {}
  local final_sections = {}

  -- 1) <initial_prompts>
  if conf.initial_prompt and conf.initial_prompt ~= "" then
    table.insert(final_sections, "<initial_prompts>\n" .. conf.initial_prompt .. "\n</initial_prompts>\n")
  end

  -- 2) <tools_available>
  table.insert(final_sections, build_tools_available_block())

  -- 3) <task>
  local task_lines = {}
  task_lines[#task_lines+1] = "<task>"
  task_lines[#task_lines+1] = user_input
  for _, file_path in ipairs(initial_files) do
    task_lines[#task_lines+1] = ("'%s' (see below for file content)"):format(file_path)
  end
  task_lines[#task_lines+1] = "</task>\n"
  table.insert(final_sections, table.concat(task_lines, "\n"))

  -- 4) <file_content path="...">
  local file_content_blocks = {}
  for _, file_path in ipairs(initial_files) do
    local full_path = root .. "/" .. file_path
    if is_subpath(root, full_path) then
      local fdata = read_file(full_path)
      if fdata then
        file_content_blocks[#file_content_blocks+1] = string.format(
          "<file_content path=\"%s\">\n%s\n</file_content>", file_path, fdata
        )
      end
    end
  end
  if #file_content_blocks > 0 then
    table.insert(final_sections, table.concat(file_content_blocks, "\n\n"))
  end

  -- 5) <environment_details>
  local env_lines = {}
  env_lines[#env_lines+1] = "<environment_details>"
  env_lines[#env_lines+1] = "# VSCode Visible Files"
  for _, f in ipairs(initial_files) do
    env_lines[#env_lines+1] = f
  end
  env_lines[#env_lines+1] = ""
  env_lines[#env_lines+1] = "# VSCode Open Tabs"
  env_lines[#env_lines+1] = "..."
  env_lines[#env_lines+1] = ""
  env_lines[#env_lines+1] = "# Current Time"
  env_lines[#env_lines+1] = os.date("%x, %X (%Z)")
  env_lines[#env_lines+1] = ""
  env_lines[#env_lines+1] = "# Current Working Directory (" .. root .. ") Files"
  env_lines[#env_lines+1] = context.get_project_structure(dirs, conf) or ""
  env_lines[#env_lines+1] = ""
  env_lines[#env_lines+1] = "# Current Mode"
  env_lines[#env_lines+1] = "ACT MODE"
  env_lines[#env_lines+1] = "</environment_details>"
  table.insert(final_sections, table.concat(env_lines, "\n"))

  return table.concat(final_sections, "\n\n")
end

local function handle_step_by_step_if_needed(prompt, conf)
  local length = #prompt
  local limit = conf.prompt_char_limit or 8000
  if (not conf.enable_step_by_step) or (length <= limit) then
    return { prompt }
  end
  return { prompts["step-prompt"] }
end

------------------------------------------------------------------------------
-- :ChatGPT
------------------------------------------------------------------------------
local function run_chatgpt_command()
  local conf = config.load()
  ui.setup_ui(conf)
  ui.debug_log("Running :ChatGPT command.")
  local dirs = conf.directories or {"."}
  if conf.interactive_file_selection then
    dirs = ui.pick_directories(dirs, conf)
    if #dirs == 0 then
      dirs = conf.directories
    end
  end

  close_existing_buffer_by_name("ChatGPT_Prompt.md$")
  local bufnr = vim.api.nvim_create_buf(false, false)
  vim.api.nvim_buf_set_name(bufnr, "ChatGPT_Prompt.md")
  vim.api.nvim_buf_set_option(bufnr, "filetype", "markdown")
  vim.api.nvim_buf_set_option(bufnr, "bufhidden", "wipe")
  vim.api.nvim_buf_set_option(bufnr, "buftype", "")
  vim.api.nvim_buf_set_option(bufnr, "modifiable", true)

  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, {
    "# Enter your main user prompt (task) below.",
    "",
    "Save & close with :wq, :x, or :bd to finalize your prompt."
  })

  vim.api.nvim_create_autocmd("BufWriteCmd", {
    buffer = bufnr,
    callback = function()
      local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
      local user_input = table.concat(lines, "\n")
      if user_input == "" or user_input:find("^# Enter your main user prompt %(task%) below.") then
        vim.api.nvim_out_write("No valid input provided.\n")
        vim.api.nvim_buf_set_option(bufnr, "modified", false)
        return
      end

      local final_prompt = build_prompt(user_input, dirs, conf)
      local chunks = handle_step_by_step_if_needed(final_prompt, conf)

      close_existing_buffer_by_name("ChatGPT_Generated_Prompt$")
      local bufnr_ref = vim.api.nvim_create_buf(false, true)
      vim.api.nvim_buf_set_name(bufnr_ref, "ChatGPT_Generated_Prompt")
      vim.api.nvim_buf_set_option(bufnr_ref, "filetype", "markdown")

      local prompt_lines = vim.split(chunks[1], "\n")
      vim.api.nvim_buf_set_lines(bufnr_ref, 0, -1, false, prompt_lines)
      vim.cmd("vsplit")
      vim.cmd("buffer " .. bufnr_ref)

      copy_to_clipboard(chunks[1])
      if #chunks == 1 then
        vim.api.nvim_out_write("Prompt copied to clipboard! Paste into ChatGPT.\n")
      else
        vim.api.nvim_out_write("Step-by-step prompt copied to clipboard!\n")
      end

      vim.api.nvim_buf_set_option(bufnr, "modified", false)
    end
  })

  vim.cmd("buffer " .. bufnr)
end

------------------------------------------------------------------------------
-- :ChatGPTPaste
------------------------------------------------------------------------------
local function run_chatgpt_paste_command()
  local conf = config.load()
  ui.setup_ui(conf)
  ui.debug_log("Running :ChatGPTPaste command.")
  print("Reading ChatGPT YAML response from clipboard...")
  local raw = handler.get_clipboard_content(conf)
  if raw == "" then
    vim.api.nvim_err_writeln("Clipboard is empty. Please copy the YAML response from ChatGPT first.")
    return
  end

  local data = parse_response(raw, conf)
  if not data then
    return
  end

  -- Check if we have tools
  if data.tools then
    -- Must also verify project name
    if not data.project_name or data.project_name ~= conf.project_name then
      vim.api.nvim_err_writeln("Project name mismatch or missing. Aborting tool usage.")
      return
    end

    local output_messages = tools_manager.handle_tool_calls(data.tools, conf, is_subpath, read_file)
    copy_to_clipboard(output_messages)
    print("Tool call results have been processed and copied to clipboard.")
    return
  end

  -- If we see project_name & files => older YAML style. We handle it but it's discouraged now.
  if data.project_name and data.files then
    if data.project_name ~= conf.project_name then
      vim.api.nvim_err_writeln("Project name mismatch. Aborting.")
      return
    end

    local is_final = false
    for _, fileinfo in ipairs(data.files) do
      if fileinfo.content or fileinfo.delete == true then
        is_final = true
        break
      end
    end

    if is_final then
      if conf.preview_changes then
        require('chatgpt_nvim.init').preview_changes(data.files, conf)
        print("Close the preview window to apply changes, or use :q to cancel.")
        local closed = vim.wait(60000, function()
          local bufs = vim.api.nvim_list_bufs()
          for _, b in ipairs(bufs) do
            local name = vim.api.nvim_buf_get_name(b)
            if name:match("ChatGPT_Changes_Preview$") then
              return false
            end
          end
          return true
        end)
        if not closed then
          vim.api.nvim_err_writeln("Preview not closed in time. Aborting.")
          return
        end
      end

      local final_files = data.files
      if conf.partial_acceptance then
        final_files = require('chatgpt_nvim.init').partial_accept(data.files, conf)
        if #final_files == 0 then
          vim.api.nvim_err_writeln("No changes remain after partial acceptance. Aborting.")
          return
        end
      end

      local root = vim.fn.getcwd()
      for _, fileinfo in ipairs(final_files) do
        if not fileinfo.path then
          vim.api.nvim_err_writeln("Invalid file entry. Must have 'path'.")
        else
          if not is_subpath(root, fileinfo.path) then
            vim.api.nvim_err_writeln("Invalid path outside project root: " .. fileinfo.path)
          else
            if fileinfo.delete == true then
              ui.debug_log("Deleting file: " .. fileinfo.path)
              handler.delete_file(fileinfo.path, conf)
              print("Deleted: " .. fileinfo.path)
            elseif fileinfo.content then
              ui.debug_log("Writing file: " .. fileinfo.path)
              handler.write_file(fileinfo.path, fileinfo.content, conf)
              print("Wrote: " .. fileinfo.path)
            else
              vim.api.nvim_err_writeln("Invalid file entry. Must have 'content' or 'delete'.")
            end
          end
        end
      end
    else
      -- Not final => user is requesting more files
      local requested_paths = {}
      local root = vim.fn.getcwd()
      for _, fileinfo in ipairs(data.files) do
        if fileinfo.path then
          table.insert(requested_paths, fileinfo.path)
        end
      end

      local file_sections = {}
      for _, f in ipairs(requested_paths) do
        local path = root .. "/" .. f
        local content = read_file(path)
        if content then
          table.insert(file_sections, ("\nFile: `%s`\n```\n%s\n```\n"):format(f, content))
        else
          table.insert(file_sections, ("\nFile: `%s`\n```\n(Could not read file)\n```\n"):format(f))
        end
      end

      local sections = {
        conf.initial_prompt,
        "\n\nProject name: " .. (conf.project_name or ""),
        "\n\nBelow are the requested files from the project, each preceded by its filename in backticks and enclosed in triple backticks.\n",
        table.concat(file_sections, "\n"),
        "\n\nIf you need more files, please respond again in YAML listing additional files, or use the 'tools:' approach. If you have all info, provide final changes or continue your instructions."
      }

      local prompt = table.concat(sections, "\n")
      local length = #prompt
      ui.debug_log("Returning requested files. Character count: " .. length)

      if length > (conf.prompt_char_limit or 8000) and conf.enable_step_by_step then
        local large_step = prompts["step-prompt"]
        copy_to_clipboard(large_step)
        print("Step-by-step guidance copied to clipboard!")
        return
      elseif length > (conf.prompt_char_limit or 8000) then
        vim.api.nvim_err_writeln("Requested files exceed prompt character limit. No step-by-step support enabled.")
        return
      end

      copy_to_clipboard(prompt)
      print("Prompt (with requested files) copied to clipboard! Paste it into ChatGPT.")
    end
  else
    vim.api.nvim_err_writeln("No tools or recognized file instructions found. Provide 'tools:' or older 'project_name & files'.")
  end
end

------------------------------------------------------------------------------
-- :ChatGPTCurrentBuffer
------------------------------------------------------------------------------
local function run_chatgpt_current_buffer_command()
  local conf = config.load()
  ui.setup_ui(conf)
  ui.debug_log("Running :ChatGPTCurrentBuffer command.")

  local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
  local user_input = table.concat(lines, "\n")
  local dirs = conf.directories or {"."}
  if conf.interactive_file_selection then
    dirs = ui.pick_directories(dirs, conf)
    if #dirs == 0 then
      dirs = conf.directories
    end
  end

  local final_prompt = build_prompt(user_input, dirs, conf)
  local chunks = handle_step_by_step_if_needed(final_prompt, conf)

  close_existing_buffer_by_name("ChatGPT_Generated_Prompt$")
  local bufnr_ref = vim.api.nvim_create_buf(false, true)
  vim.api.nvim_buf_set_name(bufnr_ref, "ChatGPT_Generated_Prompt")
  vim.api.nvim_buf_set_option(bufnr_ref, "filetype", "markdown")

  local prompt_lines = vim.split(chunks[1], "\n")
  vim.api.nvim_buf_set_lines(bufnr_ref, 0, -1, false, prompt_lines)
  vim.cmd("vsplit")
  vim.cmd("buffer " .. bufnr_ref)

  copy_to_clipboard(chunks[1])
  if #chunks == 1 then
    vim.api.nvim_out_write("Prompt (from current buffer) copied to clipboard! Paste into ChatGPT.\n")
  else
    vim.api.nvim_out_write("Step-by-step prompt (from current buffer) copied to clipboard!\n")
  end
end

------------------------------------------------------------------------------
-- PUBLIC API
------------------------------------------------------------------------------
M.run_chatgpt_command = run_chatgpt_command
M.run_chatgpt_paste_command = run_chatgpt_paste_command
M.run_chatgpt_current_buffer_command = run_chatgpt_current_buffer_command

return M