local M = {}

local config = require("gitea.config")
local api = require("gitea.api")
local auth = require("gitea.auth")

-- We'll keep detect_owner_repo() from before
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

--------------------------------------------------------------------------------
--- Data Structures to track what's in the ephemeral buffer
--------------------------------------------------------------------------------

-- We'll store some metadata for each "segment" in the buffer:
--   - The issue's title line range
--   - The issue's body line range
--   - Each existing comment (with start/end line range)
--   - Possibly space for a new comment
--
-- On save (:w), we compare what's changed and do the appropriate API calls.
--------------------------------------------------------------------------------

local function create_issue_buffer_metadata(issue)
  -- track lines for the title, the body, each comment
  local meta = {
    issue_number = issue.number,
    -- will fill in fields once we place them in the buffer
    title_start = nil,
    title_end   = nil,
    body_start  = nil,
    body_end    = nil,
    comments = {}, -- array of { id, start, end }
    new_comment_start = nil, -- where user can type a new comment
  }
  return meta
end

--------------------------------------------------------------------------------
--- RENDER ISSUE INTO BUFFER
--------------------------------------------------------------------------------
local function render_issue_into_buf(bufnr, issue, comments)
  -- We assume the buffer is empty and ephemeral.
  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, "")

  -- store line index references for metadata
  local meta = create_issue_buffer_metadata(issue)

  -- place the "title line"
  meta.title_start = #lines+1
  table.insert(lines, issue.title or "")
  meta.title_end = #lines

  -- a blank line
  table.insert(lines, "")
  -- place the "body 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

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

  local line_count = #lines
  local comment_meta = {}
  for _, c in ipairs(comments) do
    table.insert(lines, "")
    local start_line = #lines+1
    -- We'll place a small header: e.g. "Comment (ID=12345) by username"
    local author = c.user and c.user.login or c.user and c.user.username or c.user or "?"
    table.insert(lines, string.format("COMMENT #%d by %s", c.id, author))
    -- Then the actual comment body lines
    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

  -- place a blank line for user to add a new comment
  table.insert(lines, "")
  table.insert(lines, "# --- Add a new comment below this line. If you leave it blank, no new comment is created. ---")
  local new_comment_start = #lines+1
  table.insert(lines, "") -- an empty line to start from

  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)

  -- store metadata
  local b_meta = {
    issue_number = issue.number,
    title_start = meta.title_start,
    title_end   = meta.title_end,
    body_start  = meta.body_start,
    body_end    = meta.body_end,
    comments = comment_meta,
    new_comment_start = new_comment_start,
  }
  return b_meta
end

--------------------------------------------------------------------------------
--- Parse buffer changes and do API updates on save
--------------------------------------------------------------------------------
local function on_issue_buf_write(bufnr, metadata, owner, repo)
  -- read all buffer lines
  local new_lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)

  ----------------- Title update check -----------------
  local new_title = table.concat(vim.list_slice(new_lines, metadata.title_start, metadata.title_end), "\n")
  -- remove trailing newlines just in case
  new_title = new_title:gsub("%s+$", "")
  -- we do a get_issue call to see the current title
  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 = false
  if (current_issue_data.title or "") ~= new_title then
    changed_title = true
  end

  ----------------- Body update check ------------------
  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 = false
  if (current_issue_data.body or "") ~= new_body then
    changed_body = true
  end

  ----------------- Comments update check -------------
  local changed_comments = {}
  for _, cmeta in ipairs(metadata.comments) do
    local c_lines = vim.list_slice(new_lines, cmeta.start_line, cmeta.end_line)
    -- The first line is "COMMENT #<id> by <author>"
    -- The rest is the actual body
    -- e.g. `COMMENT #112 by alice`
    local first_line = c_lines[1] or ""
    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")
    -- We fetch the current comment from the server to check if changed
    -- But Gitea's issue comment API does not necessarily let us get a single comment by ID easily.
    -- Instead, we do "issue_data, with comments" or store old body in memory.

    -- For simplicity, let's store the old body in an extmark or in a table. But let's just do a naive approach:
    -- We'll assume if the line is changed, we want to patch it. We have no big reference of old body, so let's do it.

    table.insert(changed_comments, {
      id = cmeta.id,
      new_body = new_comment_body
    })
  end

  ----------------- New comment check ------------------
  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)

  -------------- Perform the updates --------------
  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

  -- for each changed comment, attempt to patch
  -- We do not do a diff, so we always do a "PATCH" if we suspect changes
  --  => If the user changed nothing, Gitea might respond 200 anyway, no big deal
  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

  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 a single ephemeral buffer for the entire Issue with comments
--------------------------------------------------------------------------------
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

  -- get all existing comments from the Gitea API
  -- for Gitea, we can do: GET /repos/{owner}/{repo}/issues/{index}/comments
  -- The plugin's `api` might have a function for that, or we can add it quickly
  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")
  vim.api.nvim_buf_set_option(buf, "filetype", "markdown")
  vim.api.nvim_buf_set_name(buf, string.format("gitea_issue_full_%d", number))

  local metadata = render_issue_into_buf(buf, issue_data, all_comments)

  -- We create an autocmd on BufWriteCmd to parse changes and do updates
  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
    -- use the same telescope approach as before:
    local has_telescope, tele = 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
          -- Instead of just editing, we now open the full timeline buffer
          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)
    -- Alternative: show a single issue by number
    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,

  -- The rest of your commands can remain or be removed as needed
  -- but presumably we can just use "show" for everything
  -- or keep an existing minimal create command, etc.
}

subcommands.pr = {
  -- We'll leave your existing PR commands as is or remove for brevity
}

--------------------------------------------------------------------------------
--- REGISTER
--------------------------------------------------------------------------------
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