[bug#61888] [PATCH] guix: add edgelist graph-backend.

[bug#61888] [PATCH] guix: add edgelist graph-backend.

[kyle]

From: Kyle Andrews <kyle@posteo.net>

* guix/graph.scm: Add csv backend.
---
 doc/guix.texi  | 14 ++++++++------
 guix/graph.scm | 21 ++++++++++++++++++++-
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 27a0c62532..09d6be4edb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -14844,16 +14844,18 @@ Invoking guix graph
 Packages and their dependencies form a @dfn{graph}, specifically a
 directed acyclic graph (DAG).  It can quickly become difficult to have a
 mental model of the package DAG, so the @command{guix graph} command
-provides a visual representation of the DAG@.  By default,
-@command{guix graph} emits a DAG representation in the input format of
+provides a visual representation of the DAG@.  By default, @command{guix
+graph} emits a DAG representation in the input format of
 @uref{https://www.graphviz.org/, Graphviz}, so its output can be passed
 directly to the @command{dot} command of Graphviz.  It can also emit an
 HTML page with embedded JavaScript code to display a ``chord diagram''
 in a Web browser, using the @uref{https://d3js.org/, d3.js} library, or
 emit Cypher queries to construct a graph in a graph database supporting
-the @uref{https://www.opencypher.org/, openCypher} query language.  With
-@option{--path}, it simply displays the shortest path between two
-packages.  The general syntax is:
+the @uref{https://www.opencypher.org/, openCypher} query language.  It
+can also emit a CSV table with the raw data required to reconstruct the
+graph using generic network analysis software like
+@uref{https://igraph.org/, igraph}. With @option{--path}, it simply
+displays the shortest path between two packages.  The general syntax is:
 
 @example
 guix graph @var{options} @var{package}@dots{}
@@ -15061,7 +15063,7 @@ Invoking guix graph
 @item --list-backends
 List the supported graph backends.
 
-Currently, the available backends are Graphviz and d3.js.
+Currently, the available backends are Graphviz, Cypher, d3.js, and csv.
 
 @item --path
 Display the shortest path between two nodes of the type specified by
diff --git a/guix/graph.scm b/guix/graph.scm
index 41219ab67d..6a3f802da9 100644
--- a/guix/graph.scm
+++ b/guix/graph.scm
@@ -255,6 +255,24 @@ (define %graphviz-backend
                  emit-prologue emit-epilogue
                  emit-node emit-edge))
 
+(define (emit-csv-prologue name port)
+  (display "table, from, to\n" port))
+
+(define (emit-csv-epilogue port)
+  (display "" port))
+
+(define (emit-csv-node id label port)
+  (format port "package, ~a, ~a\n" label id))
+
+(define (emit-csv-edge id1 id2 port)
+  (format port "depends, ~a, ~a\n" id1 id2))
+
+(define %csv-backend
+  (graph-backend "csv"
+                 "Generate graph in CSV format"
+                 emit-csv-prologue emit-csv-epilogue
+                 emit-csv-node emit-csv-edge))
+
 \f
 ;;;
 ;;; d3js export.
@@ -338,7 +356,8 @@ (define %cypher-backend
 (define %graph-backends
   (list %graphviz-backend
         %d3js-backend
-        %cypher-backend))
+        %cypher-backend
+        %csv-backend))
 
 (define (lookup-backend name)
   "Return the graph backend called NAME.  Raise an error if it is not found."
-- 
2.37.2