class WikiPagesController < ApplicationController
  rescue_from Wiki::Commit::Conflict, with: :render_wiki_conflict

  def index
    render json: WikiPage.all
  end

  def show
    render_wiki_page_or_404 WikiPage.find(params[:id])
  end

  def show_by_title
    render_wiki_page_or_404 WikiPage.find_by(title: params[:title])
  end

  def exists
    if WikiPage.exists?(params[:id])
      head :no_content
    else
      head :not_found
    end
  end

  def exists_by_title
    if WikiPage.exists?(title: params[:title])
      head :no_content
    else
      head :not_found
    end
  end

  def diff
    id = params[:id]
    return head :bad_request if id.blank?

    from = params[:from].presence
    to = params[:to].presence

    page = WikiPage.find(id)

    from_rev = from && page.wiki_revisions.find(from)
    to_rev = to ? page.wiki_revisions.find(to) : page.current_revision
    if ((from_rev && !(from_rev.content?)) || !(to_rev&.content?))
      return head :unprocessable_entity
    end

    diffs = Diff::LCS.sdiff(from_rev&.body&.lines || [], to_rev.body.lines)
    diff_json = diffs.map { |change|
      case change.action
      when ?=
        { type: 'context', content: change.old_element }
      when ?!
        [{ type: 'removed', content: change.old_element },
         { type: 'added', content: change.new_element }]
      when ?+
        { type: 'added', content: change.new_element }
      when ?-
        { type: 'removed', content: change.old_element }
      end
    }.flatten.compact

    render json: { wiki_page_id:      page.id,
                   title:             page.title,
                   older_revision_id: from_rev&.id,
                   newer_revision_id: to_rev.id,
                   diff:              diff_json }
  end

  def create
    return head :unauthorized unless current_user
    return head :forbidden unless current_user.member?

    title = params[:title]&.strip
    body = params[:body].to_s

    return head :unprocessable_entity if title.blank? || body.blank?

    page = WikiPage.new(title:, created_user: current_user, updated_user: current_user)

    if page.save
      message = params[:message].presence
      Wiki::Commit.content!(page:, body:, created_user: current_user, message:)

      render json: page, status: :created
    else
      render json: { errors: page.errors.full_messages },
             status: :unprocessable_entity
    end
  end

  def update
    return head :unauthorized unless current_user
    return head :forbidden unless current_user.member?

    title = params[:title]&.strip
    body = params[:body].to_s

    return head :unprocessable_entity if title.blank? || body.blank?

    page = WikiPage.find(params[:id])
    base_revision_id = page.current_revision.id

    if params[:title].present? && params[:title].strip != page.title
      return head :unprocessable_entity
    end

    message = params[:message].presence
    Wiki::Commit.content!(page:,
                          body:,
                          created_user: current_user,
                          message:,
                          base_revision_id:)

    head :ok
  end

  def search
    title = params[:title]&.strip

    q = WikiPage.all
    if title.present?
      q = q.where('title LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%")
    end

    render json: q.limit(20)
  end

  def changes
    id = params[:id].presence
    q = WikiRevision.includes(:wiki_page, :created_user).order(id: :desc)
    q = q.where(wiki_page_id: id) if id

    render json: q.limit(200).map { |rev|
      { revision_id:  rev.id,
        pred:         rev.base_revision_id,
        succ:         nil,
        wiki_page:    { id: rev.wiki_page_id, title: rev.wiki_page.title },
        user:         { id: rev.created_user.id, name: rev.created_user.name },
        kind:         rev.kind,
        message:      rev.message,
        timestamp:    rev.created_at }
    }.compact
  end

  private

  def render_wiki_page_or_404 page
    return head :not_found unless page

    if params[:version].present?
      rev = page.wiki_revisions.find_by(id: params[:version])
      return head :not_found unless rev

      if rev.redirect?
        return (
            redirect_to wiki_page_by_title_path(title: rev.redirect_page.title),
                        status: :moved_permanently)
      end

      body = rev.body
      revision_id = rev.id
      pred = page.pred_revision_id(revision_id)
      succ = page.succ_revision_id(revision_id)

      return render json: page.as_json.merge(body:, revision_id:, pred:, succ:)
    end

    rev = page.current_revision
    unless rev
      return render json: page.as_json.merge(body: nil, revision_id: nil, pred: nil, succ: nil)
    end

    if rev.redirect?
      return (
          redirect_to wiki_page_by_title_path(title: rev.redirect_page.title),
                      status: :moved_permanently)
    end

    body = rev.body
    revision_id = rev.id
    pred = page.pred_revision_id(revision_id)
    succ = page.succ_revision_id(revision_id)

    render json: page.as_json.merge(body:, revision_id:, pred:, succ:)
  end

  def render_wiki_conflict err
    render json: { error: 'conflict', message: err.message }, status: :conflict
  end
end