pkgs/sternenseemann: add schmecgit, a cgit about / source filter

Only does very simple dispatching to pkgs.lowdown and pkgs.chroma, but
is at least significantly faster than the default source and about
filters bundled with cgit (which is not really a challenge as they use
python and pygments).

Added to enable my cgit setup until we can have TVL's //tools/cheddar.

3 files changed, 146 insertions, 0 deletions

diff --git a/pkgs/sternenseemann/default.nix b/pkgs/sternenseemann/default.nix
index da3dcb7e..b133df65 100644
--- a/pkgs/sternenseemann/default.nix
+++ b/pkgs/sternenseemann/default.nix
@@ -57,6 +57,10 @@ lib.fix (self: {
     temp
     ;
 
+  schmecgit = callPackage ./schmecgit {
+    inherit (pkgs.llvmPackages_latest) stdenv;
+  };
+
   scripts = dontRecurseIntoAttrs (callPackage ./scripts {
     inherit (writers) writeBashBin;
     inherit (self) shakti;
diff --git a/pkgs/sternenseemann/schmecgit/default.nix b/pkgs/sternenseemann/schmecgit/default.nix
new file mode 100644
index 00000000..982b2c1d
--- /dev/null
+++ b/pkgs/sternenseemann/schmecgit/default.nix
@@ -0,0 +1,37 @@
+{ runCommandWith
+, stdenv
+, lib
+, lowdown
+, chroma
+, substituteAll
+}:
+
+let
+  src = substituteAll {
+    src = ./main.c;
+    chroma = "${lib.getBin chroma}/bin/chroma";
+    lowdown = "${lib.getBin lowdown}/bin/lowdown";
+  };
+in
+
+runCommandWith {
+  name = "schmecgit";
+  inherit stdenv;
+  derivationArgs.meta = {
+    description = "schmeck it, about and source filter for cgit";
+    license = lib.licenses.gpl2Plus;
+    platforms = lib.platforms.unix;
+  };
+} ''
+  mkdir -p "$out/bin"
+
+  # compile main executable
+  clang -o "$out/bin/schmecgit" -pedantic -Wall -Wextra -Werror -std=c99 ${src}
+
+  # wrapper script for cgit about filter
+  cat > "$out/bin/schmecgit-about" <<EOF
+  #!${stdenv.shell}
+  exec "$out/bin/schmecgit" --about \$@
+  EOF
+  chmod +x "$out/bin/schmecgit-about"
+''
diff --git a/pkgs/sternenseemann/schmecgit/main.c b/pkgs/sternenseemann/schmecgit/main.c
new file mode 100644
index 00000000..1b3b4ada
--- /dev/null
+++ b/pkgs/sternenseemann/schmecgit/main.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
+
+enum file_type {
+  PLAIN,
+  MARKDOWN,
+  HTML,
+  CODE
+};
+
+void output_xml_escaped_char(char c, FILE *out) {
+  switch(c) {
+    case '&':
+      fputs("&amp;", out);
+      break;
+    case '<':
+      fputs("&lt;", out);
+      break;
+    case '>':
+      fputs("&gt;", out);
+      break;
+    case '\'':
+      fputs("&apos;", out);
+      break;
+    case '\"':
+      fputs("&quot;", out);
+      break;
+    default:
+      fputc(c, out);
+      break;
+  }
+}
+
+int main(int argc, char *argv[]) {
+  bool about_filter;
+  char *file;
+
+  if(argc == 2) {
+    about_filter = 0;
+    file = argv[1];
+  } else if(argc == 3 && strcmp(argv[1], "--about") == 0) {
+    about_filter = 1;
+    file = argv[2];
+  } else {
+    fprintf(stderr, "Usage: %s [--about] BASENAME\n", argv[0]);
+    return 1;
+  }
+
+  char *extension = rindex(file, '.');
+  enum file_type ft = PLAIN;
+
+  if(extension != NULL) {
+    extension++;
+
+    if(about_filter && (strcmp(extension, "md") == 0 || strcmp(extension, "markdown") == 0)) {
+      ft = MARKDOWN;
+    } else if(about_filter && (strcmp(extension, "html") == 0 || strcmp(extension, "htm") == 0)) {
+      ft = HTML;
+    } else if(strcmp(extension, "txt") == 0) {
+      ft = PLAIN;
+    } else {
+      ft = CODE;
+    }
+  } else {
+    if(strcmp(file, "Makefile") == 0 || strcmp(file, "Doxyfile")) {
+      ft = CODE;
+    }
+  }
+
+  if(ft == PLAIN || ft == HTML) {
+    char c;
+    if(ft == PLAIN) {
+      fputs("<pre>", stdout);
+    }
+
+    while((c = fgetc(stdin)) != EOF) {
+      if(ft == HTML) {
+        fputc(c, stdout);
+      } else {
+        output_xml_escaped_char(c, stdout);
+      }
+    }
+
+    if(ft == PLAIN) {
+      fputs("</pre>", stdout);
+    }
+  } else if(ft == MARKDOWN) {
+    return execl("@lowdown@", "lowdown", NULL);
+  } else if(ft == CODE) {
+    return execl(
+      "@chroma@", "chroma", "--filename", file,
+      "--html", "--html-tab-width=2", "--html-only", "--html-inline-styles",
+      "--style=lovelace",
+      NULL
+    );
+  } else {
+    return 1;
+  }
+
+  return 0;
+}