local M = {}

local config = require("gitea.config")
local api = require("gitea.api")
local auth = require("gitea.auth")
local highlights = require("gitea.highlights")  -- we still require highlights

------------------------------------------------------------------------------
-- DETECT OWNER/REPO
------------------------------------------------------------------------------
local function detect_owner_repo()
  local cmd = "git config remote.origin.url"
  local url = vim.fn.systemlist(cmd)[1]
  if vim.v.shell_error ~= 0 or not url or url == "" then
    return nil, nil
  end
  url = url:gsub("%.git$", "")
  local _, after = url:match("^(https?://)(.*)$")
  if after then
    local path = after:match("[^/]+/(.*)$")
    if not path then
      return nil, nil
    end
    local owner, repo = path:match("^(.-)/(.*)$")
    return owner, repo
  end
  local user_host, path = url:match("^(.-):(.*)$")
  if user_host and path then
    local owner, repo = path:match("^(.-)/(.*)$")
    return owner, repo
  end
  return nil, nil
end

------------------------------------------------------------------------------
-- BUFFER METADATA
------------------------------------------------------------------------------
local function create_issue_buffer_metadata(issue)
  return {
    issue_number = issue.number,
    title_start  = nil,
    title_end    = nil,
    body_start   = nil,
    body_end     = nil,
    comments     = {}, -- each = { id, start_line, end_line }
    new_comment_start = nil,
  }
end

------------------------------------------------------------------------------
-- APPLY HIGHLIGHTS
------------------------------------------------------------------------------
local function apply_issue_highlights(bufnr, meta)
  -- The first line in the file is line 0 in Lua’s API, so we subtract 1
  -- from meta.* to convert to 0-based indexing.

  ------------------------------------------------------------------------
  -- Lines #0 & #1 hold meta info (“# Gitea Issue #...”, “# STATE: ...”)
  ------------------------------------------------------------------------
  vim.api.nvim_buf_add_highlight(bufnr, 0, "GiteaIssueMeta", 0, 0, -1)
  vim.api.nvim_buf_add_highlight(bufnr, 0, "GiteaIssueMeta", 1, 0, -1)

  ------------------------------------------------------------------------
  -- Title
  ------------------------------------------------------------------------
  local title_line_0 = meta.title_start - 1
  vim.api.nvim_buf_add_highlight(bufnr, 0, "GiteaIssueTitle", title_line_0, 0, -1)

  ------------------------------------------------------------------------
  -- Body lines
  ------------------------------------------------------------------------
  -- meta.body_start .. meta.body_end (inclusive, 1-based)
  for line = meta.body_start, meta.body_end do
    local line_0 = line - 1
    vim.api.nvim_buf_add_highlight(bufnr, 0, "GiteaCommentBody", line_0, 0, -1)
  end

  ------------------------------------------------------------------------
  -- Comment headings & bodies
  ------------------------------------------------------------------------
  for _, c in ipairs(meta.comments) do
    -- The heading line has “COMMENT #123 by user”
    local heading_line_0 = c.start_line - 1
    vim.api.nvim_buf_add_highlight(bufnr, 0, "GiteaCommentHeading", heading_line_0, 0, -1)

    -- The actual comment text is lines [heading_line_0+1 .. c.end_line-1]
    for text_line = (c.start_line + 1), c.end_line do
      local text_line_0 = text_line - 1
      vim.api.nvim_buf_add_highlight(bufnr, 0, "GiteaCommentBody", text_line_0, 0, -1)
    end
  end
end

------------------------------------------------------------------------------
-- RENDER ISSUE INTO BUFFER
------------------------------------------------------------------------------
local function render_issue_into_buf(bufnr, issue, comments)
  local lines = {}
  table.insert(lines, string.format("# Gitea Issue #%d: %s", issue.number, issue.title))
  table.insert(lines, "# STATE: " .. (issue.state or "unknown"))
  table.insert(lines, "# Edit the title below, then the body, then any comments.")
  table.insert(lines, "# On save (:w), changes to the title/body will be updated; changes to comment lines will be updated, and new text at the bottom becomes a new comment.")
  table.insert(lines, "")

  local meta = create_issue_buffer_metadata(issue)
  meta.title_start = #lines + 1
  table.insert(lines, issue.title or "")
  meta.title_end = #lines

  table.insert(lines, "")
  meta.body_start = #lines + 1
  if issue.body then
    local body_lines = vim.split(issue.body, "\n", true)
    if #body_lines == 0 then
      table.insert(lines, "")
    else
      for _, l in ipairs(body_lines) do
        table.insert(lines, l)
      end
    end
  else
    table.insert(lines, "No issue description.")
  end
  meta.body_end = #lines

  table.insert(lines, "")
  table.insert(lines, "# --- Comments ---")

  local comment_meta = {}
  for _, c in ipairs(comments) do
    table.insert(lines, "")
    local start_line = #lines + 1
    local author = c.user and (c.user.login or c.user.username) or "?"
    table.insert(lines, string.format("COMMENT #%d by %s", c.id, author))

    local c_body_lines = vim.split(c.body or "", "\n", true)
    if #c_body_lines == 0 then
      table.insert(lines, "")
    else
      for _, cb in ipairs(c_body_lines) do
        table.insert(lines, cb)
      end
    end
    local end_line = #lines
    table.insert(comment_meta, {
      id = c.id,
      start_line = start_line,
      end_line   = end_line,
    })
  end

  table.insert(lines, "")
  table.insert(lines, "# --- Add a new comment below this line. If you leave it blank, no new comment is created. ---")
  meta.new_comment_start = #lines + 1
  table.insert(lines, "")

  -- Save comment meta
  meta.comments = comment_meta

  -- Put all lines into the buffer
  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)

  -- Now apply highlight groups
  apply_issue_highlights(bufnr, meta)

  return meta
end

------------------------------------------------------------------------------
-- ON SAVE (BufWriteCmd)
------------------------------------------------------------------------------
local function on_issue_buf_write(bufnr, metadata, owner, repo)
  local new_lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
  local new_title = table.concat(vim.list_slice(new_lines, metadata.title_start, metadata.title_end), "\n")
  new_title = new_title:gsub("%s+$", "")

  local current_issue_data = api.get_issue(owner, repo, metadata.issue_number)
  if not current_issue_data then
    vim.notify("[gitea.nvim] Could not re-fetch the issue to verify updates", vim.log.levels.ERROR)
    return
  end

  local changed_title = (current_issue_data.title or "") ~= new_title
  local new_body_lines = vim.list_slice(new_lines, metadata.body_start, metadata.body_end)
  local new_body = table.concat(new_body_lines, "\n")
  local changed_body = (current_issue_data.body or "") ~= new_body

  local changed_comments = {}
  for _, cmeta in ipairs(metadata.comments) do
    local c_lines = vim.list_slice(new_lines, cmeta.start_line, cmeta.end_line)
    -- first line => "COMMENT #<id> by <author>"
    local c_body = {}
    for i = 2, #c_lines do
      table.insert(c_body, c_lines[i])
    end
    local new_comment_body = table.concat(c_body, "\n")
    table.insert(changed_comments, {
      id       = cmeta.id,
      new_body = new_comment_body
    })
  end

  local new_comment_body_lines = {}
  for i = metadata.new_comment_start, #new_lines do
    table.insert(new_comment_body_lines, new_lines[i])
  end
  local new_comment_body = table.concat(new_comment_body_lines, "\n"):gsub("^%s+", ""):gsub("%s+$", "")
  local create_new_comment = (#new_comment_body > 0)

  -- Edit issue if title or body changed
  if changed_title or changed_body then
    local updated, st = api.edit_issue(owner, repo, metadata.issue_number, {
      title = changed_title and new_title or current_issue_data.title,
      body  = changed_body and new_body  or current_issue_data.body,
    })
    if updated then
      vim.notify("[gitea.nvim] Issue updated!")
    else
      vim.notify(string.format("[gitea.nvim] Failed to update issue (HTTP %s).", st or "?"), vim.log.levels.ERROR)
    end
  end

  -- Edit each comment
  for _, cupd in ipairs(changed_comments) do
    local updated_comment, st = api.edit_issue_comment(owner, repo, metadata.issue_number, cupd.id, cupd.new_body)
    if not updated_comment then
      vim.notify(string.format("[gitea.nvim] Failed to update comment %d. (HTTP %s)", cupd.id, st or "?"), vim.log.levels.ERROR)
    else
      vim.notify(string.format("[gitea.nvim] Comment #%d updated.", cupd.id))
    end
  end

  -- Possibly add a new comment
  if create_new_comment then
    local created, st = api.comment_issue(owner, repo, metadata.issue_number, new_comment_body)
    if created then
      vim.notify("[gitea.nvim] New comment posted.")
    else
      vim.notify(string.format("[gitea.nvim] Failed to create new comment (HTTP %s).", st or "?"), vim.log.levels.ERROR)
    end
  end
end

------------------------------------------------------------------------------
-- OPEN ISSUE BUFFER
------------------------------------------------------------------------------
local function open_full_issue_buffer(owner, repo, number)
  local issue_data, status = api.get_issue(owner, repo, number)
  if not issue_data then
    vim.notify(string.format("[gitea.nvim] Error retrieving issue #%d (HTTP %s).", number, status or "?"), vim.log.levels.ERROR)
    return
  end

  local all_comments, cstatus = api.get_issue_comments(owner, repo, number)
  if not all_comments then
    vim.notify(string.format("[gitea.nvim] Error retrieving issue #%d comments (HTTP %s).", number, cstatus or "?"), vim.log.levels.ERROR)
    return
  end

  local buf = vim.api.nvim_create_buf(false, true)
  vim.api.nvim_buf_set_option(buf, "buftype", "acwrite")

  -- Use our new "gitea" filetype, so after/syntax/gitea.vim will load
  vim.api.nvim_buf_set_option(buf, "filetype", "gitea")

  vim.api.nvim_buf_set_name(buf, string.format("gitea_issue_full_%d", number))

  -- Load highlight definitions (e.g. GiteaIssueTitle, GiteaCommentBody, etc.)
  highlights.setup()

  local metadata = render_issue_into_buf(buf, issue_data, all_comments)

  -- Auto command to handle saving
  vim.api.nvim_create_autocmd("BufWriteCmd", {
    buffer = buf,
    callback = function()
      on_issue_buf_write(buf, metadata, owner, repo)
    end
  })

  vim.api.nvim_set_current_buf(buf)
end

------------------------------------------------------------------------------
-- SUBCOMMANDS
------------------------------------------------------------------------------
local subcommands = {}

subcommands.issue = {
  list = function(args)
    local owner, repo = detect_owner_repo()
    if not owner or not repo then
      vim.notify("[gitea.nvim] Could not detect owner/repo.", vim.log.levels.ERROR)
      return
    end
    local has_telescope, _ = pcall(require, "telescope")
    if not has_telescope then
      vim.notify("[gitea.nvim] telescope.nvim is not installed", vim.log.levels.ERROR)
      return
    end

    local pickers = require("telescope.pickers")
    local finders = require("telescope.finders")
    local conf = require("telescope.config").values
    local actions = require("telescope.actions")
    local action_state = require("telescope.actions.state")

    local issues, status = api.list_issues(owner, repo, {})
    if not issues then
      vim.notify(string.format("[gitea.nvim] Error fetching issues (HTTP %s).", status or "?"), vim.log.levels.ERROR)
      return
    end

    pickers.new({}, {
      prompt_title = string.format("Issues: %s/%s", owner, repo),
      finder = finders.new_table {
        results = issues,
        entry_maker = function(issue)
          return {
            value = issue,
            display = string.format("#%d  %s", issue.number, issue.title),
            ordinal = issue.number .. " " .. issue.title
          }
        end
      },
      sorter = conf.generic_sorter({}),
      attach_mappings = function(prompt_bufnr, map)
        local function select_issue()
          local selection = action_state.get_selected_entry()
          actions.close(prompt_bufnr)
          if not selection or not selection.value then
            return
          end
          open_full_issue_buffer(owner, repo, selection.value.number)
        end
        map("i", "<CR>", select_issue)
        map("n", "<CR>", select_issue)
        return true
      end,
    }):find()
  end,

  show = function(args)
    local number = tonumber(args[1])
    if not number then
      vim.notify("[gitea.nvim] Usage: :Gitea issue show <number>", vim.log.levels.ERROR)
      return
    end
    local owner, repo = detect_owner_repo()
    if not owner or not repo then
      vim.notify("[gitea.nvim] Could not detect owner/repo.", vim.log.levels.ERROR)
      return
    end
    open_full_issue_buffer(owner, repo, number)
  end,
}

subcommands.pr = {
  -- your other PR-related commands, if any
}

------------------------------------------------------------------------------
-- REGISTER COMMAND
------------------------------------------------------------------------------
function M.register()
  vim.api.nvim_create_user_command("Gitea", function(cmd_opts)
    auth.ensure_token()
    local args = {}
    for w in string.gmatch(cmd_opts.args, "%S+") do
      table.insert(args, w)
    end
    local object = args[1]
    local action = args[2]
    if not object then
      print("Usage: :Gitea <object> <action> [args]")
      print("Examples:")
      print("  :Gitea issue list")
      print("  :Gitea issue show 123")
      return
    end
    local sc = subcommands[object]
    if not sc then
      vim.notify("[gitea.nvim] Unknown object: "..object, vim.log.levels.ERROR)
      return
    end
    if not action then
      vim.notify("[gitea.nvim] Please specify an action for "..object, vim.log.levels.ERROR)
      return
    end
    local fn = sc[action]
    if not fn then
      vim.notify(string.format("[gitea.nvim] Unknown action '%s' for object '%s'", action, object), vim.log.levels.ERROR)
      return
    end
    table.remove(args, 1) -- remove object
    table.remove(args, 1) -- remove action
    fn(args)
  end, {
    nargs = "*",
    complete = function(arg_lead, cmd_line, cursor_pos)
      local parts = vim.split(cmd_line, "%s+")
      if #parts == 2 then
        local objs = {}
        for k, _ in pairs(subcommands) do
          if k:match("^"..arg_lead) then
            table.insert(objs, k)
          end
        end
        return objs
      elseif #parts == 3 then
        local object = parts[2]
        local acts = {}
        if subcommands[object] then
          for k, _ in pairs(subcommands[object]) do
            if k:match("^"..arg_lead) then
              table.insert(acts, k)
            end
          end
        end
        return acts
      else
        return {}
      end
    end
  })
end

return M