Created IAC reverse generator
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p2913020
203
src/iac_reverse/generator/variable_extractor.py
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203
src/iac_reverse/generator/variable_extractor.py
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"""Variable extraction logic for Terraform code generation.
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Identifies attribute values that appear in 2+ resources and extracts them
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into Terraform variables with appropriate type expressions and defaults.
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"""
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import logging
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from collections import defaultdict
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from iac_reverse.models import DiscoveredResource, ExtractedVariable
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logger = logging.getLogger(__name__)
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def _infer_type_expr(value: object) -> str:
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"""Infer a Terraform type expression from a Python value.
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Args:
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value: The Python value to infer a type for.
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Returns:
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A Terraform type expression string (e.g., "string", "number", "bool").
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"""
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if isinstance(value, bool):
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return "bool"
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elif isinstance(value, int) or isinstance(value, float):
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return "number"
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elif isinstance(value, str):
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return "string"
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elif isinstance(value, list):
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return "list(string)"
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elif isinstance(value, dict):
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return "map(string)"
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else:
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return "string"
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def _format_default_value(value: object) -> str:
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"""Format a Python value as a Terraform default value literal.
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Args:
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value: The Python value to format.
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Returns:
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A string representation suitable for a Terraform variable default.
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"""
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if isinstance(value, bool):
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return "true" if value else "false"
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elif isinstance(value, int) or isinstance(value, float):
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return str(value)
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elif isinstance(value, str):
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return f'"{value}"'
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elif isinstance(value, list):
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items = ", ".join(f'"{item}"' if isinstance(item, str) else str(item) for item in value)
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return f"[{items}]"
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elif isinstance(value, dict):
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entries = ", ".join(f'"{k}" = "{v}"' for k, v in value.items())
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return "{" + entries + "}"
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else:
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return f'"{value}"'
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def _make_hashable(value: object) -> object:
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"""Convert a value to a hashable representation for counting.
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Args:
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value: Any Python value from resource attributes.
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Returns:
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A hashable version of the value.
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"""
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if isinstance(value, dict):
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return tuple(sorted(value.items()))
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elif isinstance(value, list):
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return tuple(value)
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else:
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return value
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class VariableExtractor:
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"""Extracts shared attribute values into Terraform variables.
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Scans a list of DiscoveredResource objects, identifies attribute values
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that appear in 2 or more resources, and creates ExtractedVariable instances
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for each shared value.
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"""
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def extract_variables(
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self, resources: list[DiscoveredResource]
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) -> list[ExtractedVariable]:
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"""Identify shared attribute values and extract them as variables.
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For each attribute key, collects all values across all resources.
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If a value appears in 2+ resources for the same attribute key,
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it becomes a variable with the most common value as the default.
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Args:
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resources: List of discovered resources to analyze.
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Returns:
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List of ExtractedVariable instances for shared values.
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"""
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if len(resources) < 2:
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return []
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# Collect attribute values grouped by attribute key
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# key -> {hashable_value -> [list of (resource_unique_id, original_value)]}
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attr_values: dict[str, dict[object, list[tuple[str, object]]]] = defaultdict(
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lambda: defaultdict(list)
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)
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for resource in resources:
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for attr_key, attr_value in resource.attributes.items():
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# Skip complex nested structures (dicts/lists) for variable extraction
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# as they are less likely to be meaningfully shared
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if isinstance(attr_value, (dict, list)):
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continue
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hashable = _make_hashable(attr_value)
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attr_values[attr_key][hashable].append(
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(resource.unique_id, attr_value)
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)
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# Build extracted variables for values appearing in 2+ resources
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variables: list[ExtractedVariable] = []
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for attr_key, value_groups in sorted(attr_values.items()):
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# Find all values that appear in 2+ resources for this key
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shared_values = [
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(hv, entries)
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for hv, entries in value_groups.items()
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if len(entries) >= 2
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]
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if not shared_values:
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continue
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# If only one shared value exists for this key, use the key as the var name
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# If multiple shared values exist, disambiguate with a suffix
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for idx, (hashable_value, resource_entries) in enumerate(shared_values):
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original_value = resource_entries[0][1]
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used_by = [entry[0] for entry in resource_entries]
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# Determine the most common value among the shared values for this key
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# The default is set to the most common value overall
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most_common_entries = max(shared_values, key=lambda x: len(x[1]))
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most_common_value = most_common_entries[1][0][1]
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# Use the most common value as default for the primary variable,
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# but each variable's default is its own value
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default_value = _format_default_value(original_value)
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if len(shared_values) == 1:
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var_name = f"var_{attr_key}"
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else:
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# Disambiguate when multiple shared values exist for same key
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var_name = f"var_{attr_key}_{idx}"
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type_expr = _infer_type_expr(original_value)
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description = (
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f"Shared {attr_key} value extracted from "
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f"{len(resource_entries)} resources"
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)
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variables.append(
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ExtractedVariable(
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name=var_name,
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type_expr=type_expr,
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default_value=default_value,
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description=description,
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used_by=used_by,
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)
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)
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return variables
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def generate_variables_tf(
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self, variables: list[ExtractedVariable]
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) -> str:
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"""Generate Terraform variables.tf file content.
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Produces variable blocks with type, description, and default values.
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Args:
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variables: List of extracted variables to render.
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Returns:
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String content for a variables.tf file.
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"""
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if not variables:
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return ""
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blocks: list[str] = []
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for var in variables:
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block = (
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f'variable "{var.name}" {{\n'
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f' type = {var.type_expr}\n'
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f' description = "{var.description}"\n'
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f' default = {var.default_value}\n'
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f'}}'
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)
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blocks.append(block)
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return "\n\n".join(blocks) + "\n"
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