defmodule PhoenixKit.Modules.Publishing.StaleFixer do
  @moduledoc """
  Fixes stale or invalid values on publishing records.

  Validates and corrects fields like mode, type, status, language, and
  timestamps across groups, posts, versions, and content. Also reconciles
  status consistency between posts, versions, and content rows.
  """

  require Logger

  import Ecto.Query, only: [from: 2]

  alias PhoenixKit.Modules.Languages
  alias PhoenixKit.Modules.Publishing.DBStorage
  alias PhoenixKit.Modules.Publishing.LanguageHelpers
  alias PhoenixKit.Modules.Publishing.PublishingGroup
  alias PhoenixKit.Modules.Publishing.PublishingPost

  alias PhoenixKit.Modules.Publishing.Constants

  # Posts younger than this are skipped by the stale fixer's empty-post deletion
  @grace_period_seconds 300

  @valid_types Constants.valid_types()
  @valid_group_modes Constants.valid_modes()
  @valid_post_statuses Constants.post_statuses()
  @valid_group_statuses Constants.group_statuses()
  @valid_version_statuses Constants.content_statuses()
  @default_group_mode Constants.default_mode()
  @default_group_type Constants.default_type()

  @type_item_names %{
    "blog" => {"post", "posts"},
    "faq" => {"question", "questions"},
    "legal" => {"document", "documents"}
  }
  @default_item_singular "item"
  @default_item_plural "items"

  @doc """
  Fixes stale or invalid values on a publishing group record.

  Checks and corrects:
  - `mode` — must be "timestamp" or "slug" (defaults to "timestamp")
  - `data.type` — must be in valid_types (defaults to "custom")
  - `data.item_singular` — must be a non-empty string (defaults based on type)
  - `data.item_plural` — must be a non-empty string (defaults based on type)

  Can be called explicitly or runs lazily when groups are loaded in the admin.
  Returns the group unchanged if no fixes are needed.
  """
  @spec fix_stale_group(PublishingGroup.t()) :: PublishingGroup.t()
  def fix_stale_group(%PublishingGroup{} = group) do
    attrs = build_group_fixes(group)
    apply_stale_fix(group, attrs, &DBStorage.update_group/2)
  end

  defp build_group_fixes(group) do
    data = group.data || %{}
    type = Map.get(data, "type", @default_group_type)
    fixed_type = if type in @valid_types, do: type, else: "custom"
    fixed_mode = if group.mode in @valid_group_modes, do: group.mode, else: @default_group_mode
    fixed_status = if group.status in @valid_group_statuses, do: group.status, else: "active"

    {default_singular, default_plural} = default_item_names(fixed_type)
    item_singular = Map.get(data, "item_singular")
    item_plural = Map.get(data, "item_plural")

    fixed_singular = valid_string_or_default(item_singular, default_singular)
    fixed_plural = valid_string_or_default(item_plural, default_plural)

    data_changes =
      data
      |> maybe_update("type", type, fixed_type)
      |> maybe_update("item_singular", item_singular, fixed_singular)
      |> maybe_update("item_plural", item_plural, fixed_plural)

    attrs = if data_changes != data, do: %{data: data_changes}, else: %{}
    attrs = if fixed_mode != group.mode, do: Map.put(attrs, :mode, fixed_mode), else: attrs
    if fixed_status != group.status, do: Map.put(attrs, :status, fixed_status), else: attrs
  end

  defp valid_string_or_default(val, default) do
    if is_binary(val) and val != "", do: val, else: default
  end

  @doc """
  Fixes stale or invalid values on a publishing post record.

  Checks and corrects:
  - `primary_language` — must be a recognized language code. Resolution order:
    1. Tries to resolve a dialect (e.g., "en" → "en-US")
    2. Falls back to the first available language on the post
    3. Falls back to the system primary language
  - `status` — must be a valid post status (defaults to "draft")
  - `mode` — must be "timestamp" or "slug" (defaults to "timestamp")
  - `post_date`/`post_time` — must be present for timestamp mode posts

  Only fixes languages not in the master predefined list — languages that were
  added, used, then removed from enabled are left untouched.
  """
  @spec fix_stale_post(PublishingPost.t()) :: PublishingPost.t()
  def fix_stale_post(%PublishingPost{} = post) do
    # Pre-fetch all versions and contents once to avoid redundant queries
    ctx = build_post_context(post)
    do_fix_stale_post(post, ctx)
  end

  defp build_post_context(post) do
    versions = DBStorage.list_versions(post.uuid)
    version_uuids = Enum.map(versions, & &1.uuid)
    contents_by_version = DBStorage.batch_load_contents(version_uuids)
    %{versions: versions, contents_by_version: contents_by_version}
  end

  defp do_fix_stale_post(post, ctx) do
    # Hard-delete empty posts (no content in any version) — they're abandoned
    # drafts with no recoverable content, so trashing them just creates a
    # restore → auto-trash loop. Skip recently created posts to avoid killing
    # posts before the editor has had a chance to autosave.
    if empty_post?(ctx) and past_grace_period?(post) do
      Logger.info("[Publishing] Deleting empty post #{post.uuid} (no content in any version)")
      DBStorage.delete_post(post)
      post
    else
      post = apply_stale_fix(post, build_post_fixes(post, ctx), &DBStorage.update_post/2)

      # Fix version/content-level issues, also fix stale versions and contents
      fix_missing_primary_content(post, ctx)
      fix_multiple_published_versions(post, ctx)
      fix_translation_status_consistency(post, ctx)

      for version <- ctx.versions do
        fix_stale_version(version)
        contents = Map.get(ctx.contents_by_version, version.uuid, [])
        Enum.each(contents, &fix_stale_content/1)
      end

      DBStorage.get_post_by_uuid(post.uuid, [:group]) || post
    end
  end

  defp empty_post?(ctx) do
    if ctx.versions == [] do
      true
    else
      Enum.all?(ctx.versions, fn version ->
        contents = Map.get(ctx.contents_by_version, version.uuid, [])

        contents == [] or
          Enum.all?(contents, fn c ->
            (c.content || "") == "" and (c.title || "") in ["", Constants.default_title()]
          end)
      end)
    end
  end

  defp past_grace_period?(post) do
    case post.inserted_at do
      nil -> true
      inserted_at -> DateTime.diff(DateTime.utc_now(), inserted_at) >= @grace_period_seconds
    end
  end

  defp build_post_fixes(post, ctx) do
    %{}
    |> maybe_fix_post_language(post, ctx)
    |> maybe_fix_post_status(post)
    |> maybe_fix_post_mode(post)
    |> maybe_fix_post_slug(post, ctx)
    |> maybe_fix_post_timestamp(post)
  end

  defp maybe_fix_post_language(attrs, post, ctx) do
    case fix_stale_language(post, ctx) do
      nil -> attrs
      fixed_lang -> Map.put(attrs, :primary_language, fixed_lang)
    end
  end

  defp maybe_fix_post_status(attrs, post) do
    cond do
      post.status in @valid_post_statuses -> attrs
      # Convert removed "scheduled" status to "draft"
      post.status == "scheduled" -> Map.put(attrs, :status, "draft")
      true -> Map.put(attrs, :status, "draft")
    end
  end

  defp maybe_fix_post_mode(attrs, post) do
    # First ensure the mode is a valid value
    fixed_mode = if post.mode in @valid_group_modes, do: post.mode, else: @default_group_mode

    # Then sync with the group's mode if they differ (e.g., group switched from
    # timestamp to slug but existing posts were never updated)
    group = if post.group, do: post.group, else: DBStorage.get_group(post.group_uuid)

    fixed_mode =
      if group && group.mode in @valid_group_modes do
        group.mode
      else
        fixed_mode
      end

    if fixed_mode != post.mode, do: Map.put(attrs, :mode, fixed_mode), else: attrs
  end

  defp maybe_fix_post_slug(attrs, post, ctx) do
    effective_mode = attrs[:mode] || post.mode

    if effective_mode == "slug" and (is_nil(post.slug) or post.slug == "") do
      # Post switched to slug mode but has no slug — generate from title or date
      base_slug = generate_slug_for_post(post, ctx)

      if base_slug != "" do
        # Ensure uniqueness by checking if slug exists in the group
        slug = ensure_unique_slug(post.group_uuid, base_slug, post.uuid)

        Logger.info(
          "[Publishing] Generating slug for post #{post.uuid}: #{inspect(slug)} (mode changed to slug)"
        )

        Map.put(attrs, :slug, slug)
      else
        Logger.warning(
          "[Publishing] Failed to generate slug for post #{post.uuid} — post will be unreachable in slug mode"
        )

        attrs
      end
    else
      attrs
    end
  end

  # Ensures a slug is unique within a group by appending a UUID suffix if needed
  defp ensure_unique_slug(group_uuid, slug, post_uuid) do
    conflict =
      from(p in PublishingPost,
        where: p.group_uuid == ^group_uuid and p.slug == ^slug and p.uuid != ^post_uuid,
        select: p.uuid,
        limit: 1
      )
      |> PhoenixKit.RepoHelper.repo().one()

    if conflict do
      suffix = String.slice(post_uuid || "", 0, 8)
      "#{slug}-#{suffix}"
    else
      slug
    end
  end

  defp generate_slug_for_post(post, ctx) do
    # Try to get title from the latest version's primary content
    title =
      case ctx.versions do
        [] ->
          nil

        versions ->
          latest = List.last(versions)
          contents = Map.get(ctx.contents_by_version, latest.uuid, [])

          case Enum.find(contents, &(&1.language == post.primary_language)) do
            nil -> nil
            content -> content.title
          end
      end

    base =
      cond do
        is_binary(title) and title not in ["", Constants.default_title()] ->
          title

        post.post_date ->
          Date.to_iso8601(post.post_date)

        true ->
          "post-#{String.slice(post.uuid || "", 0, 8)}"
      end

    base
    |> String.downcase()
    |> String.replace(~r/[^a-z0-9]+/u, "-")
    |> String.trim("-")
  end

  defp maybe_fix_post_timestamp(attrs, post) do
    if (attrs[:mode] || post.mode) == "timestamp" do
      now = DateTime.utc_now()

      attrs
      |> then(fn a ->
        if is_nil(post.post_date), do: Map.put(a, :post_date, DateTime.to_date(now)), else: a
      end)
      |> then(fn a ->
        if is_nil(post.post_time),
          do: Map.put(a, :post_time, Time.new!(now.hour, now.minute, 0)),
          else: a
      end)
    else
      attrs
    end
  end

  # Returns the fixed language or nil if no fix needed.
  defp fix_stale_language(post, ctx) do
    lang = post.primary_language

    if lang && Languages.get_predefined_language(lang) do
      nil
    else
      fixed = resolve_stale_language(lang, ctx)
      if fixed != lang, do: fixed, else: nil
    end
  end

  defp resolve_stale_language(lang, ctx) do
    dialect = if lang, do: Languages.DialectMapper.base_to_dialect(lang), else: nil

    if dialect && Languages.get_predefined_language(dialect) do
      dialect
    else
      available = post_available_languages(ctx)

      if available != [] do
        Enum.find(available, hd(available), fn code ->
          Languages.get_predefined_language(code) != nil
        end)
      else
        LanguageHelpers.get_primary_language()
      end
    end
  end

  defp post_available_languages(ctx) do
    case ctx.versions do
      [] ->
        []

      [first | _] ->
        contents = Map.get(ctx.contents_by_version, first.uuid, [])
        Enum.map(contents, & &1.language)
    end
  end

  defp apply_stale_fix(record, attrs, _update_fn) when attrs == %{}, do: record

  defp apply_stale_fix(record, attrs, update_fn) do
    identifier = Map.get(record, :uuid) || Map.get(record, :slug) || "unknown"

    Logger.info(
      "[Publishing] Fixing stale values for #{record.__struct__} #{identifier}: #{inspect(attrs)}"
    )

    case update_fn.(record, attrs) do
      {:ok, updated} ->
        updated

      {:error, reason} ->
        Logger.warning(
          "[Publishing] Failed to fix stale values for #{identifier}: #{inspect(reason)}"
        )

        record
    end
  end

  defp maybe_update(data, key, old_val, new_val) do
    if old_val != new_val, do: Map.put(data, key, new_val), else: data
  end

  @doc """
  Fixes stale values across all groups, posts, versions, and content.
  Also reconciles status consistency between posts, versions, and content,
  fixes missing primary language content, and ensures single published version.
  Callable via internal API or IEx.
  """
  @spec fix_all_stale_values() :: :ok
  def fix_all_stale_values do
    # Scan ALL groups (including trashed) — pass nil to skip status filter
    groups = DBStorage.list_groups(nil)
    Enum.each(groups, &fix_stale_group/1)

    for group <- groups do
      posts = DBStorage.list_posts(group.slug)
      Enum.each(posts, &fix_stale_post/1)
    end

    :ok
  end

  def fix_stale_version(version) do
    if version.status not in @valid_version_statuses do
      Logger.info(
        "[Publishing] Fixing stale version #{version.uuid}: status #{inspect(version.status)} → \"draft\""
      )

      DBStorage.update_version(version, %{status: "draft"})
    end
  end

  def fix_stale_content(content) do
    attrs =
      %{}
      |> maybe_fix_content_status(content)
      |> maybe_fix_content_language(content)

    if attrs != %{} do
      Logger.info(
        "[Publishing] Fixing stale content #{content.uuid} (#{content.language}): #{inspect(attrs)}"
      )

      DBStorage.update_content(content, attrs)
    end
  end

  defp maybe_fix_content_status(attrs, content) do
    if content.status in @valid_version_statuses,
      do: attrs,
      else: Map.put(attrs, :status, "draft")
  end

  defp maybe_fix_content_language(attrs, content) do
    if is_binary(content.language) and content.language != "" do
      attrs
    else
      Map.put(attrs, :language, LanguageHelpers.get_primary_language())
    end
  end

  @doc """
  Fixes missing primary language content.

  If the primary language has no content (or empty content) but a translation
  exists with content, copies the best translation to the primary language
  and inherits its status.
  """
  def fix_missing_primary_content(%PublishingPost{} = post) do
    ctx = build_post_context(post)
    fix_missing_primary_content(post, ctx)
  end

  defp fix_missing_primary_content(post, ctx) do
    primary_lang = post.primary_language

    for version <- ctx.versions do
      contents = Map.get(ctx.contents_by_version, version.uuid, [])
      primary_content = Enum.find(contents, &(&1.language == primary_lang))

      if primary_content_missing?(primary_content) and contents != [] do
        fix_version_primary_content(post, version, primary_lang, primary_content, contents)
      end
    end
  end

  defp primary_content_missing?(nil), do: true

  defp primary_content_missing?(content) do
    content.content in [nil, ""] and content.title in [nil, "", Constants.default_title()]
  end

  defp fix_version_primary_content(post, version, primary_lang, primary_content, contents) do
    source = find_best_translation(contents, primary_lang)

    if source do
      Logger.info(
        "[Publishing] Fixing missing primary content for post #{post.uuid}/v#{version.version_number}: " <>
          "copying from #{source.language} to #{primary_lang}"
      )

      copy_translation_to_primary(version, primary_lang, primary_content, source)
      maybe_promote_post_to_published(post, source)
    end
  end

  defp find_best_translation(contents, primary_lang) do
    Enum.find(contents, fn c ->
      c.language != primary_lang and c.status == "published" and c.content not in [nil, ""]
    end) ||
      Enum.find(contents, fn c ->
        c.language != primary_lang and c.content not in [nil, ""]
      end)
  end

  defp copy_translation_to_primary(version, primary_lang, nil, source) do
    DBStorage.create_content(%{
      version_uuid: version.uuid,
      language: primary_lang,
      title: source.title,
      content: source.content,
      status: source.status,
      url_slug: source.url_slug
    })
  end

  defp copy_translation_to_primary(_version, _primary_lang, primary_content, source) do
    DBStorage.update_content(primary_content, %{
      title: source.title,
      content: source.content,
      status: source.status,
      url_slug: primary_content.url_slug || source.url_slug
    })
  end

  defp maybe_promote_post_to_published(post, source) do
    if source.status == "published" and post.status != "published" do
      Logger.info(
        "[Publishing] Promoting post #{post.uuid} to published (primary content now has published content)"
      )

      DBStorage.update_post(post, %{
        status: "published",
        published_at: post.published_at || DateTime.utc_now()
      })
    end
  end

  @doc """
  Ensures only one version is published per post.

  If multiple versions have status "published", keeps the highest version
  number as published and archives the rest.
  """
  def fix_multiple_published_versions(%PublishingPost{} = post) do
    ctx = build_post_context(post)
    fix_multiple_published_versions(post, ctx)
  end

  defp fix_multiple_published_versions(post, ctx) do
    published = Enum.filter(ctx.versions, &(&1.status == "published"))

    if length(published) > 1 do
      # Keep the highest version number, archive the rest
      sorted = Enum.sort_by(published, & &1.version_number, :desc)
      [keep | demote] = sorted

      Logger.info(
        "[Publishing] Post #{post.uuid} has #{length(published)} published versions, " <>
          "keeping v#{keep.version_number}, archiving #{length(demote)} others"
      )

      for v <- demote do
        DBStorage.update_version(v, %{status: "archived"})
        DBStorage.update_content_status(v.uuid, "archived")
      end
    end
  end

  @doc """
  Ensures translation statuses follow the primary language's status.

  If the primary language content is not published (draft/archived/trashed)
  but a translation is published, demotes the translation to match the
  primary's status. Translations should never be published when the primary isn't.
  """
  def fix_translation_status_consistency(%PublishingPost{} = post) do
    ctx = build_post_context(post)
    fix_translation_status_consistency(post, ctx)
  end

  defp fix_translation_status_consistency(post, ctx) do
    primary_lang = post.primary_language

    for version <- ctx.versions do
      contents = Map.get(ctx.contents_by_version, version.uuid, [])
      primary_content = Enum.find(contents, &(&1.language == primary_lang))

      primary_status = if primary_content, do: primary_content.status, else: post.status

      if primary_status != "published" do
        # Demote any translations that are published when primary isn't
        for content <- contents,
            content.language != primary_lang,
            content.status == "published" do
          Logger.info(
            "[Publishing] Demoting translation #{content.language} from published to #{primary_status} " <>
              "for post #{post.uuid}/v#{version.version_number} (primary is #{primary_status})"
          )

          DBStorage.update_content(content, %{status: primary_status})
        end
      end
    end
  end

  # Reconciles status consistency between a post, its versions, and content.
  #
  # Rules enforced:
  # 1. Post "published" requires at least one "published" version → else demote to "draft"
  # 2. Version "published" requires its post to be "published" → else archive the version
  # 3. Content "published" requires its version to be "published" → else demote to "draft"
  # 4. Non-published versions cannot have "published" content → demote content to "draft"
  #
  # Note: individual translations CAN be "draft" while the version is "published" —
  # this is the normal state for untranslated languages. We only fix content that
  # claims to be "published" when it shouldn't be.
  def reconcile_post_status(%PublishingPost{} = post) do
    # Re-read to get current state after individual fixes
    post = DBStorage.get_post_by_uuid(post.uuid) || post
    versions = DBStorage.list_versions(post.uuid)

    published_versions = Enum.filter(versions, &(&1.status == "published"))

    cond do
      # Post says published but no version backs it up
      post.status == "published" and published_versions == [] ->
        Logger.info(
          "[Publishing] Reconcile: post #{post.uuid} is published but has no published versions, demoting to draft"
        )

        DBStorage.update_post(post, %{status: "draft"})

      # Post is not published but a version claims to be — archive the version
      post.status in ["draft", "archived", "trashed"] and published_versions != [] ->
        Logger.info(
          "[Publishing] Reconcile: post #{post.uuid} is #{inspect(post.status)} but has #{length(published_versions)} published versions, archiving"
        )

        for v <- published_versions do
          DBStorage.update_version(v, %{status: "archived"})
          demote_published_content(v.uuid)
        end

      true ->
        :ok
    end

    # For ALL non-published versions, no content should be "published"
    non_published_versions = Enum.reject(versions, &(&1.status == "published"))

    for v <- non_published_versions do
      demote_published_content(v.uuid)
    end
  end

  # Demotes any "published" content rows to "draft" within a version.
  # Leaves "draft" and "archived" content untouched.
  defp demote_published_content(version_uuid) do
    contents = DBStorage.list_contents(version_uuid)
    published = Enum.filter(contents, &(&1.status == "published"))

    if published != [] do
      Logger.info(
        "[Publishing] Demoting #{length(published)} published content row(s) to \"draft\" in version #{version_uuid}"
      )

      for content <- published do
        DBStorage.update_content(content, %{status: "draft"})
      end
    end
  end

  # Returns the default item names for a given type.
  defp default_item_names(type) do
    Map.get(@type_item_names, type, {@default_item_singular, @default_item_plural})
  end
end