From 304b4b274c69251dce75ab50e7abb6372c2a3772 Mon Sep 17 00:00:00 2001
From: NunoSempere <nuno.sempere@protonmail.com>
Date: Tue, 13 Dec 2022 20:04:18 +0000
Subject: [PATCH] feat: minimal redirection functionality.

---
 plugins/libre_redirect/build-example.sh    |  11 ++++
 plugins/libre_redirect/example             | Bin 0 -> 17008 bytes
 plugins/libre_redirect/example.c           |  25 +++++++++
 plugins/libre_redirect/libre_redirect.c    |  47 +++++++++++++++++
 plugins/libre_redirect/libre_redirect.h    |   8 +++
 plugins/libre_redirect/str_replace_start.c |  58 +++++++++++++++++++++
 plugins/libre_redirect/str_replace_start.h |   6 +++
 7 files changed, 155 insertions(+)
 create mode 100644 plugins/libre_redirect/build-example.sh
 create mode 100755 plugins/libre_redirect/example
 create mode 100644 plugins/libre_redirect/example.c
 create mode 100644 plugins/libre_redirect/libre_redirect.c
 create mode 100755 plugins/libre_redirect/libre_redirect.h
 create mode 100755 plugins/libre_redirect/str_replace_start.c
 create mode 100755 plugins/libre_redirect/str_replace_start.h

diff --git a/plugins/libre_redirect/build-example.sh b/plugins/libre_redirect/build-example.sh
new file mode 100644
index 0000000..ac7cf4a
--- /dev/null
+++ b/plugins/libre_redirect/build-example.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+CC=gcc
+
+FLAGS="-std=c99 -Wall -lm"
+
+SRC=example.c
+REQS="str_replace_start.c libre_redirect.c"
+
+echo -e "\n\n\n"
+$CC $FLAGS $SRC $REQS -o example
+
diff --git a/plugins/libre_redirect/example b/plugins/libre_redirect/example
new file mode 100755
index 0000000000000000000000000000000000000000..d46dfae22428a6a3c376a3b9935e8da1f5356b2e
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diff --git a/plugins/libre_redirect/example.c b/plugins/libre_redirect/example.c
new file mode 100644
index 0000000..b21cad1
--- /dev/null
+++ b/plugins/libre_redirect/example.c
@@ -0,0 +1,25 @@
+#include "libre_redirect.h"
+#include <string.h>
+#include <stdio.h>
+
+int main(){
+  char uri[] = "https://reddit.com/r/blah";
+
+  int uri_length = strlen(uri);
+  int l = LIBRE_N+uri_length;
+  char uri_filtered[l++];
+  for(int i=0; i<l; i++){
+    uri_filtered[i] = ' ';
+  }
+  uri_filtered[l] = '\0';
+
+  int libre_check = libre_redirect(uri, uri_filtered);
+  if(!libre_check){
+    printf("Filtered url: %s", uri_filtered);
+  }else{
+    printf("Uri: %s", uri);
+    // failure; do something with the original uri.
+  }
+}
+
+
diff --git a/plugins/libre_redirect/libre_redirect.c b/plugins/libre_redirect/libre_redirect.c
new file mode 100644
index 0000000..7d18387
--- /dev/null
+++ b/plugins/libre_redirect/libre_redirect.c
@@ -0,0 +1,47 @@
+#include "str_replace_start.h"
+#include <string.h>
+#define LIBRE_N 12
+
+/* Inspired by https://libredirect.github.io/, but in C. */
+
+// int str_replace_start(const char* string, const char* target, const char* replacement, char* output){
+
+int libre_redirect(const char* uri, char* output){
+  /* inv.riverside.rocks */
+  // max length
+  int l1 = strlen(uri);
+  int l2 = strlen(output);
+  
+  if((l2 - l1) < LIBRE_N){ 
+    return 1; // not enough memory. 
+  }else{
+    char tmp_uri[l2++];
+    strcpy(tmp_uri, uri);
+
+    char* sites[] = { 
+      "https://youtube.com", 
+      "https://reddit.com", 
+      "https://medium.com", 
+      "https://translate.google.com" 
+    };
+    char* alternatives[] = { 
+      "https://yt.artemislena.eu", 
+      "https://teddit.nunosempere.com", 
+      "https://scribe.rip", 
+      "https://simplytranslate.org/" 
+    };
+
+    for(int i=1; i<4; i++){
+      int replace_check = str_replace_start(tmp_uri, sites[i], alternatives[i], output);
+      if(replace_check){
+        return 1;
+      }
+      strcpy(tmp_uri, output);
+    }
+    strcpy(output, tmp_uri);
+
+  }
+
+  return 0;
+  
+}
diff --git a/plugins/libre_redirect/libre_redirect.h b/plugins/libre_redirect/libre_redirect.h
new file mode 100755
index 0000000..ef5cf77
--- /dev/null
+++ b/plugins/libre_redirect/libre_redirect.h
@@ -0,0 +1,8 @@
+#ifndef LIBRE_REDIRECT
+#define LIBRE_REDIRECT
+
+#define LIBRE_N 12
+
+int libre_redirect(const char* uri, char* uri_filtered);
+
+#endif
diff --git a/plugins/libre_redirect/str_replace_start.c b/plugins/libre_redirect/str_replace_start.c
new file mode 100755
index 0000000..70f9567
--- /dev/null
+++ b/plugins/libre_redirect/str_replace_start.c
@@ -0,0 +1,58 @@
+#include <string.h>
+#include <stdbool.h>
+#include <stdio.h>
+#define DEBUG false
+
+/*
+See also: 
+* <https://web.archive.org/web/20160201212501/coding.debuntu.org/c-implementing-str_replace-replace-all-occurrences-substring>
+* https://github.com/irl/la-cucina/blob/master/str_replace.c
+*/
+
+int str_replace_start(const char* string, const char* target, const char* replacement, char* output){
+  /* Checks */
+  int l1 = strlen(string);
+  int l2 = strlen(target);
+  int l3 = strlen(replacement);
+  int l4 = strlen(output);
+  if(DEBUG) printf("%d,%d,%d,%d\n", l1, l2, l3, l4);
+  
+  if((l4 < (l1 - l2 + l3)) || l4 < l1 ){
+    // Not enough memory in output string.
+    if(DEBUG) printf("Case 1.\n");
+    return 1; 
+  } 
+  else if(l1 < l2){
+    // Not even possible that there is a match.
+    if(DEBUG) printf("Case 2.\n");
+    strcpy(output, string);
+  } 
+  else {
+    if(DEBUG) printf("Case 3.\n");
+    int match = true;
+    for(int i=0; i<l2; i++){
+      if(string[i] != target[i]){
+	match = false;
+	break;
+      }
+    }
+    if(match){
+      if(DEBUG) printf("Case 3.a.\n");
+      for(int i=0; i<l3; i++){
+	output[i] = replacement[i];
+      }
+      int counter = l3;
+      for(int i=l2; i<l1; i++){
+        output[counter] = string[i];
+        counter++;
+      }
+      output[counter] = '\0';
+    }
+    else {
+      if(DEBUG) printf("Case 3.b.\n");
+      strcpy(output, string);
+    }
+  }
+
+  return 0;
+}
diff --git a/plugins/libre_redirect/str_replace_start.h b/plugins/libre_redirect/str_replace_start.h
new file mode 100755
index 0000000..d9f1235
--- /dev/null
+++ b/plugins/libre_redirect/str_replace_start.h
@@ -0,0 +1,6 @@
+#ifndef STR_REPLACE_H_
+#define STR_REPLACE_H_
+
+int str_replace_start(const char* string, const char* target, const char* replacement, char* output);
+
+#endif