% This package serves the purpose of providing a way
% for relating entries in the bibliography to the license
% under which those entries where licensed. For this end
% it uses the build in biblatex 'related' mechanism to
% link works to their license. It therefor defines a new
% 'relatedtype', which is 'license'.
% 
% Anselm Wagner (a.wagner1@uni-wuppertal.de)
%
% This material is subject to the LaTeX Project Public License 1.3c.
% https://ctan.org/license/lppl1.3
% 
\NeedsTeXFormat{LaTeX2e}[1994/06/01]
\ProvidesPackage{biblatex-license}
  [2020/01/30 v1.0 biblatex-license]
\RequirePackage{biblatex}
\RequirePackage{kvoptions}
\SetupKeyvalOptions{
  family=biblicense,
  prefix=biblicense@}
\DeclareStringOption[short]{license} % how should the licenses be printed in
                                     % bib? Options: short, full, off
\DeclareBoolOption[false]{url} % should the url of the license be printed
                               % as well?
\DeclareBoolOption[true]{link} % should the lincense be a weblink?
\DeclareStringOption[default]{introtext} % alternative introtext for licenses
                                         % in the bibliography. Arbitrary text.
\ProcessKeyvalOptions*

\ifbiblicense@link % link=true
  \RequirePackage{hyperref}
\fi

% set related=true otherwise this package has no functionality
\ExecuteBibliographyOptions{related=true}

% Common definitions:
\NewBibliographyString{licensedunder}
\DefineBibliographyStrings{english}{%
  licensedunder = {licensed under},
}
\DefineBibliographyStrings{german}{%
  licensedunder = {Lizenziert unter},
}

\newbibmacro*{shortIfShorttitleExists}{%
    \iffieldundef{shorttitle}
    {\printfield{title}}
    {\printfield{shorttitle}}
}

\newbibmacro*{licenseAsLink}{\printfield[licenseAsLink]{url}}

\DeclareFieldFormat{licenseAsLink}{\href{#1}{\usebibmacro{shortIfShorttitleExists}\unspace}}

% test if alternative introtext was entered and change accordingly
\ifnum\pdf@strcmp{\biblicense@introtext}{default}=0%
    \newcommand{\biblicenseintrotext}{\biblstring{licensedunder}}
\else
    \newcommand{\biblicenseintrotext}{\biblicense@introtext}
\fi


\ifnum\pdf@strcmp{\biblicense@license}{off}=0% Package has no functionality.
  \newbibmacro*{related:license}[1]{}
\else % license is to be printed
  \ifnum\pdf@strcmp{\biblicense@license}{short}=0% short license to be printed
    \ifbiblicense@url % url=true
      \newbibmacro*{related:license}[1]{%
        \entrydata{#1}{%
          \printtext{\biblicenseintrotext}%
          \setunit{\addspace}%
          \usebibmacro{shortIfShorttitleExists}%
          \iffieldundef{url}
          {}
          {\setunit{\addspace}\usebibmacro{url}}}%
      }
    \else % url=false
      \ifbiblicense@link % link=true
        \newbibmacro*{related:license}[1]{%
          \entrydata{#1}{%
            \printtext{\biblicenseintrotext}%
            \setunit{\addspace}%
            \iffieldundef{url}
            {\usebibmacro{shortIfShorttitleExists}}
            {\usebibmacro{licenseAsLink}}%
          }
        }
      \else % link=false
        \newbibmacro*{related:license}[1]{%
          \entrydata{#1}{%
            \printtext{\biblicenseintrotext}%
            \setunit{\addspace}%
            {\usebibmacro{shortIfShorttitleExists}}%
          }
        }
      \fi % link = ?
    \fi % url = ?
  \else % license=full -- full license to be printed
      \newbibmacro*{related:license}[1]{%
          \entrydata{#1}{%
              \printtext{\biblicenseintrotext}%
              \setunit{\addspace}%
              \usedriver
              {\ifnameundef{savedauthor}
                  {\ifnameundef{savededitor}
                      {}
                      {\ifnamesequal{editor}{savededitor}
                      {\clearname{editor}}
                      {}}}
                  {\ifnamesequal{author}{savedauthor}
                      {\clearname{author}}
                      {}}%
              \renewbibmacro*{related:init}{}%
              \DeclareNameAlias{sortname}{default}%
              \ifbibmacroundef{date+extradate}
                  {}
                  {\renewbibmacro*{date+extradate}{}%
                  \renewbibmacro*{date}{\printdate}}%
              \renewbibmacro*{pageref}{}}
              {\thefield{entrytype}}
          }
      }
  \fi
\fi