feature: added conditionals + added examples

1 files changed, 371 insertions, 0 deletions

diff --git a/src/template.c b/src/template.c
index 20cf10b..bd88de0 100644
--- a/src/template.c
+++ b/src/template.c
@@ -526,6 +526,198 @@ static char *parse_indexed_tag(const char *tag_content, int *index_val) {
   return key_name;
 }
 
+typedef enum {
+  CONDITION_NONE,
+  CONDITION_TRUTHY,
+  CONDITION_EXISTS,
+  CONDITION_EQUAL,
+  CONDITION_NOT_EQUAL,
+} ConditionType;
+
+typedef struct {
+  ConditionType type;
+  char var_name[MAX_KEY_LEN];
+  char compare_value[MAX_VALUE_LEN];
+  bool negate;
+} Condition;
+
+static bool evaluate_condition(const Condition *cond, TemplateContext *ctx) {
+  if (cond == NULL || cond->type == CONDITION_NONE) {
+    return false;
+  }
+
+  ContextVar *var = find_context_var(ctx, cond->var_name);
+  const char *var_value = NULL;
+
+  if (var == NULL) {
+    if (cond->type == CONDITION_TRUTHY) {
+      return false;
+    }
+    var_value = "";
+  } else if (var->type == CONTEXT_TYPE_STRING) {
+    var_value = var->value.string_val;
+  } else {
+    if (cond->type == CONDITION_TRUTHY) {
+      return false;
+    }
+    var_value = "";
+  }
+
+  switch (cond->type) {
+  case CONDITION_TRUTHY:
+    return (var_value != NULL && strlen(var_value) > 0);
+
+  case CONDITION_EXISTS: {
+    bool exists = (var != NULL);
+    return cond->negate ? !exists : exists;
+  }
+
+  case CONDITION_EQUAL:
+    return (strcmp(var_value, cond->compare_value) == 0);
+
+  case CONDITION_NOT_EQUAL:
+    return (strcmp(var_value, cond->compare_value) != 0);
+
+  default:
+    return false;
+  }
+}
+
+static Condition parse_condition(const char *condition_str) {
+  Condition cond;
+  cond.type = CONDITION_NONE;
+  cond.var_name[0] = '\0';
+  cond.compare_value[0] = '\0';
+  cond.negate = false;
+
+  if (condition_str == NULL || *condition_str == '\0') {
+    return cond;
+  }
+
+  const char *eq_pos = strstr(condition_str, "==");
+  const char *neq_pos = strstr(condition_str, "!=");
+
+  if (eq_pos != NULL && neq_pos != NULL) {
+    if (eq_pos < neq_pos) {
+      neq_pos = NULL;
+    } else {
+      eq_pos = NULL;
+    }
+  }
+
+  if (eq_pos != NULL) {
+    size_t var_len = eq_pos - condition_str;
+    if (var_len >= MAX_KEY_LEN) {
+      var_len = MAX_KEY_LEN - 1;
+    }
+    strncpy(cond.var_name, condition_str, var_len);
+    cond.var_name[var_len] = '\0';
+
+    const char *value_start = eq_pos + 2;
+    while (*value_start == ' ' || *value_start == '\t') {
+      value_start++;
+    }
+
+    if (*value_start == '"') {
+      value_start++;
+      const char *value_end = strchr(value_start, '"');
+      if (value_end != NULL) {
+        size_t val_len = value_end - value_start;
+        if (val_len >= MAX_VALUE_LEN) {
+          val_len = MAX_VALUE_LEN - 1;
+        }
+        strncpy(cond.compare_value, value_start, val_len);
+        cond.compare_value[val_len] = '\0';
+      }
+    } else {
+      size_t val_len = strlen(value_start);
+      if (val_len >= MAX_VALUE_LEN) {
+        val_len = MAX_VALUE_LEN - 1;
+      }
+      strncpy(cond.compare_value, value_start, val_len);
+      cond.compare_value[val_len] = '\0';
+    }
+
+    cond.type = CONDITION_EQUAL;
+  } else if (neq_pos != NULL) {
+    size_t var_len = neq_pos - condition_str;
+    if (var_len >= MAX_KEY_LEN) {
+      var_len = MAX_KEY_LEN - 1;
+    }
+    strncpy(cond.var_name, condition_str, var_len);
+    cond.var_name[var_len] = '\0';
+
+    const char *value_start = neq_pos + 2;
+    while (*value_start == ' ' || *value_start == '\t') {
+      value_start++;
+    }
+
+    if (*value_start == '"') {
+      value_start++;
+      const char *value_end = strchr(value_start, '"');
+      if (value_end != NULL) {
+        size_t val_len = value_end - value_start;
+        if (val_len >= MAX_VALUE_LEN) {
+          val_len = MAX_VALUE_LEN - 1;
+        }
+        strncpy(cond.compare_value, value_start, val_len);
+        cond.compare_value[val_len] = '\0';
+      }
+    } else {
+      size_t val_len = strlen(value_start);
+      if (val_len >= MAX_VALUE_LEN) {
+        val_len = MAX_VALUE_LEN - 1;
+      }
+      strncpy(cond.compare_value, value_start, val_len);
+      cond.compare_value[val_len] = '\0';
+    }
+
+    cond.type = CONDITION_NOT_EQUAL;
+  } else if (strncmp(condition_str, "exists ", 7) == 0) {
+    const char *var_start = condition_str + 7;
+    while (*var_start == ' ' || *var_start == '\t') {
+      var_start++;
+    }
+    size_t var_len = strlen(var_start);
+    if (var_len >= MAX_KEY_LEN) {
+      var_len = MAX_KEY_LEN - 1;
+    }
+    strncpy(cond.var_name, var_start, var_len);
+    cond.var_name[var_len] = '\0';
+    cond.type = CONDITION_EXISTS;
+  } else if (strncmp(condition_str, "not exists ", 11) == 0) {
+    const char *var_start = condition_str + 11;
+    while (*var_start == ' ' || *var_start == '\t') {
+      var_start++;
+    }
+    size_t var_len = strlen(var_start);
+    if (var_len >= MAX_KEY_LEN) {
+      var_len = MAX_KEY_LEN - 1;
+    }
+    strncpy(cond.var_name, var_start, var_len);
+    cond.var_name[var_len] = '\0';
+    cond.type = CONDITION_EXISTS;
+    cond.negate = true;
+  } else {
+    size_t var_len = strlen(condition_str);
+    if (var_len >= MAX_KEY_LEN) {
+      var_len = MAX_KEY_LEN - 1;
+    }
+    strncpy(cond.var_name, condition_str, var_len);
+    cond.var_name[var_len] = '\0';
+    cond.type = CONDITION_TRUTHY;
+  }
+
+  char *p = cond.var_name;
+  char *end = cond.var_name + strlen(cond.var_name) - 1;
+  while (p < end && (*end == ' ' || *end == '\t')) {
+    *end = '\0';
+    end--;
+  }
+
+  return cond;
+}
+
 static char *render_template_segment(const char *template_segment,
                                      TemplateContext *ctx) {
   size_t initial_max_len = BUFFER_SIZE;
@@ -738,6 +930,185 @@ static char *render_template_segment(const char *template_segment,
                       "matching '{{for}}'. Appending endfor tag as-is.\n");
     }
 
+    else if (strncmp(trimmed_tag_content, "if ", 3) == 0) {
+      const char *condition_str = trimmed_tag_content + 3;
+      Condition cond = parse_condition(condition_str);
+
+      const char *else_tag = NULL;
+      const char *elif_tag = NULL;
+      const char *endif_tag = NULL;
+
+      int if_depth = 1;
+      const char *search_pos = end_tag + 2;
+      while (*search_pos != '\0' && if_depth > 0) {
+        const char *next_if = strstr(search_pos, "{{if ");
+        const char *next_else = strstr(search_pos, "{{else}}");
+        const char *next_elif = strstr(search_pos, "{{elif ");
+        const char *next_endif = strstr(search_pos, "{{endif}}");
+
+        const char *candidates[4] = {next_if, next_else, next_elif, next_endif};
+        const char *earliest = NULL;
+        int earliest_idx = -1;
+        
+        for (int i = 0; i < 4; i++) {
+          if (candidates[i] != NULL) {
+            if (earliest == NULL || candidates[i] < earliest) {
+              earliest = candidates[i];
+              earliest_idx = i;
+            }
+          }
+        }
+
+        if (earliest == NULL) {
+          break;
+        }
+
+        if (earliest_idx == 0) {
+          if_depth++;
+          search_pos = earliest + strlen("{{if ");
+          continue;
+        } else if (earliest_idx == 1) {
+          else_tag = earliest;
+          search_pos = earliest + strlen("{{else}}");
+          continue;
+        } else if (earliest_idx == 2) {
+          if (elif_tag == NULL) {
+            elif_tag = earliest;
+          }
+          search_pos = earliest + strlen("{{elif ");
+          const char *elif_end = strstr(search_pos, "}}");
+          if (elif_end != NULL) {
+            search_pos = elif_end + 2;
+          }
+          continue;
+        } else {
+          if_depth--;
+          if (if_depth == 0) {
+            endif_tag = earliest;
+          }
+          search_pos = earliest + strlen("{{endif}}");
+          continue;
+        }
+      }
+
+      if (endif_tag == NULL) {
+        fprintf(stderr,
+                "[ERROR] render_template_segment: Unclosed '{{if}}' tag. "
+                "Skipping if block.\n");
+        current_pos = end_tag + 2;
+        free(tag_content_raw);
+        continue;
+      }
+
+      if (endif_tag == NULL) {
+        fprintf(stderr,
+                "[ERROR] render_template_segment: Unclosed '{{if}}' tag. "
+                "Skipping if block.\n");
+        current_pos = end_tag + 2;
+        free(tag_content_raw);
+        continue;
+      }
+
+      bool condition_met = evaluate_condition(&cond, ctx);
+
+      const char *block_start = end_tag + 2;
+      const char *block_end = NULL;
+
+      if (condition_met) {
+        if (elif_tag != NULL && elif_tag < endif_tag) {
+          block_end = elif_tag;
+        } else if (else_tag != NULL) {
+          block_end = else_tag;
+        } else {
+          block_end = endif_tag;
+        }
+      } else {
+        bool elif_matched = false;
+        if (elif_tag != NULL && elif_tag < endif_tag) {
+          const char *test_elif = elif_tag;
+          while (test_elif != NULL && test_elif < endif_tag) {
+            const char *elif_cond_start = test_elif + strlen("{{elif ");
+            const char *elif_cond_end = strstr(elif_cond_start, "}}");
+            if (elif_cond_end == NULL || elif_cond_end >= endif_tag) {
+              break;
+            }
+
+            size_t elif_cond_len = elif_cond_end - elif_cond_start;
+            char *elif_cond_str = (char *)malloc(elif_cond_len + 1);
+            if (elif_cond_str != NULL) {
+              strncpy(elif_cond_str, elif_cond_start, elif_cond_len);
+              elif_cond_str[elif_cond_len] = '\0';
+
+              Condition elif_cond = parse_condition(elif_cond_str);
+              if (evaluate_condition(&elif_cond, ctx)) {
+                block_start = test_elif + strlen("{{elif ");
+                const char *elif_end = strstr(block_start, "}}");
+                if (elif_end != NULL) {
+                  block_start = elif_end + 2;
+                }
+                block_end = else_tag ? else_tag : endif_tag;
+                elif_matched = true;
+                free(elif_cond_str);
+                break;
+              }
+              free(elif_cond_str);
+            }
+
+            test_elif = strstr(test_elif + strlen("{{elif "), "{{elif ");
+            if (test_elif == NULL || test_elif >= endif_tag) {
+              break;
+            }
+          }
+        }
+
+        if (!elif_matched) {
+          if (else_tag && else_tag < endif_tag) {
+            block_start = else_tag + strlen("{{else}}");
+            block_end = endif_tag;
+          } else {
+            block_end = endif_tag;
+          }
+        }
+      }
+
+      size_t block_len = block_end - block_start;
+      if (block_len > 0) {
+        char *block_template = (char *)malloc(block_len + 1);
+        if (block_template != NULL) {
+          strncpy(block_template, block_start, block_len);
+          block_template[block_len] = '\0';
+
+          char *rendered_block = render_template_segment(block_template, ctx);
+          if (rendered_block != NULL) {
+            append_to_buffer(&rendered_buffer, &current_len, &max_len,
+                             rendered_block);
+            free(rendered_block);
+          }
+          free(block_template);
+        }
+      }
+
+      current_pos = endif_tag + strlen("{{endif}}");
+      free(tag_content_raw);
+      continue;
+    }
+
+    else if (strcmp(trimmed_tag_content, "elif ") == 0 ||
+             strcmp(trimmed_tag_content, "elif") == 0) {
+      fprintf(stderr, "[WARNING] render_template_segment: '{{elif}}' without "
+                      "matching '{{if}}'. Appending elif tag as-is.\n");
+    }
+
+    else if (strcmp(trimmed_tag_content, "else") == 0) {
+      fprintf(stderr, "[WARNING] render_template_segment: '{{else}}' without "
+                      "matching '{{if}}'. Appending else tag as-is.\n");
+    }
+
+    else if (strcmp(trimmed_tag_content, "endif") == 0) {
+      fprintf(stderr, "[WARNING] render_template_segment: '{{endif}}' without "
+                      "matching '{{if}}'. Appending endif tag as-is.\n");
+    }
+
     else if (strncmp(trimmed_tag_content, "include ", 8) == 0) {
       const char *filename_start = trimmed_tag_content + strlen("include ");
       if (*filename_start == '"') {