FEAT: NEW WORKFLOW ENGINE (#3160)

Co-authored-by: Joel <iamjoel007@gmail.com>
Co-authored-by: Yeuoly <admin@srmxy.cn>
Co-authored-by: JzoNg <jzongcode@gmail.com>
Co-authored-by: StyleZhang <jasonapring2015@outlook.com>
Co-authored-by: jyong <jyong@dify.ai>
Co-authored-by: nite-knite <nkCoding@gmail.com>
Co-authored-by: jyong <718720800@qq.com>

api/core/workflow/utils/variable_template_parser.py

@@ -0,0 +1,58 @@
+import re
+
+from core.workflow.entities.variable_entities import VariableSelector
+
+REGEX = re.compile(r"\{\{(#[a-zA-Z0-9_]{1,50}(\.[a-zA-Z_][a-zA-Z0-9_]{0,29}){1,10}#)\}\}")
+
+
+class VariableTemplateParser:
+    """
+    Rules:
+
+    1. Template variables must be enclosed in `{{}}`.
+    2. The template variable Key can only be: #node_id.var1.var2#.
+    3. The template variable Key cannot contain new lines or spaces, and must comply with rule 2.
+    """
+
+    def __init__(self, template: str):
+        self.template = template
+        self.variable_keys = self.extract()
+
+    def extract(self) -> list:
+        # Regular expression to match the template rules
+        matches = re.findall(REGEX, self.template)
+
+        first_group_matches = [match[0] for match in matches]
+
+        return list(set(first_group_matches))
+
+    def extract_variable_selectors(self) -> list[VariableSelector]:
+        variable_selectors = []
+        for variable_key in self.variable_keys:
+            remove_hash = variable_key.replace('#', '')
+            split_result = remove_hash.split('.')
+            if len(split_result) < 2:
+                continue
+
+            variable_selectors.append(VariableSelector(
+                variable=variable_key,
+                value_selector=split_result
+            ))
+
+        return variable_selectors
+
+    def format(self, inputs: dict, remove_template_variables: bool = True) -> str:
+        def replacer(match):
+            key = match.group(1)
+            value = inputs.get(key, match.group(0))  # return original matched string if key not found
+
+            if remove_template_variables:
+                return VariableTemplateParser.remove_template_variables(value)
+            return value
+
+        prompt = re.sub(REGEX, replacer, self.template)
+        return re.sub(r'<\|.*?\|>', '', prompt)
+
+    @classmethod
+    def remove_template_variables(cls, text: str):
+        return re.sub(REGEX, r'{\1}', text)