Convert Loopback 3 to Loopback 4 model

convert_lb3_to_lb4.py

# Updated function to handle missing `base` property in the model JSON files.
def convert_lb3_to_lb4(lb3_model_content):
    model_name = lb3_model_content['name']
    base_model = lb3_model_content.get('base', 'Entity')
    base_model = 'Entity' if base_model == 'PersistedModel' else base_model
    
    # Start building the TypeScript model
    ts_model = f"import {{Entity, hasMany, hasOne, belongsTo, model, property}} from '@loopback/repository';\n"
    
    # Collect imports for related models
    related_models = set()
    for relation in lb3_model_content.get('relations', {}).values():
        related_models.add(relation['model'])
        if 'through' in relation:
            related_models.add(relation['through'])
    
    for rel_model in related_models:
        ts_model += f"import {{{rel_model}}} from './{rel_model.lower()}.model';\n"
    
    ts_model += "\n"
    
    # Start the class definition
    ts_model += f"@model({{\n"
    ts_model += f"  settings: {{\n"
    
    # Add model settings
    if 'strict' in lb3_model_content.get('settings', {}):
        ts_model += f"    strict: {lb3_model_content['settings']['strict']},\n"
    
    if 'validateUpsert' in lb3_model_content.get('options', {}):
        ts_model += f"    validateUpsert: {str(lb3_model_content['options']['validateUpsert']).lower()},\n"
    
    if 'mongodb' in lb3_model_content.get('settings', {}):
        ts_model += f"    mongodb: {lb3_model_content['settings']['mongodb']},\n"
    
    ts_model += f"  }},\n"
    ts_model += f"}})\n"
    ts_model += f"export class {model_name} extends {base_model} {{\n"
    
    # Add properties
    for prop_name, prop_details in lb3_model_content.get('properties', {}).items():
        if isinstance(prop_details, dict):
            prop_type = prop_details['type']
            required = prop_details.get('required', False)
            ts_model += f"  @property({{\n"
            ts_model += f"    type: '{prop_type}',\n"
            if required:
                ts_model += f"    required: true,\n"
            ts_model += f"  }})\n"
            ts_model += f"  {prop_name}?: {prop_type};\n\n"
    
    # Add relations
    for rel_name, rel_details in lb3_model_content.get('relations', {}).items():
        relation_type = rel_details['type']
        related_model = rel_details['model']
        foreign_key = rel_details.get('foreignKey', None)
        through_model = rel_details.get('through', None)
        
        relation_decorator = ''
        if relation_type == 'hasMany':
            relation_decorator = f"@hasMany(() => {related_model}"
            if through_model and isinstance(through_model, dict):
                relation_decorator += f", {{through: () => {through_model['model']}}}"
            elif foreign_key:
                relation_decorator += f", {{keyTo: '{foreign_key}'}}"
            relation_decorator += ")"
        
        elif relation_type == 'hasOne':
            relation_decorator = f"@hasOne(() => {related_model}"
            if foreign_key:
                relation_decorator += f", {{keyTo: '{foreign_key}'}}"
            relation_decorator += ")"
        
        elif relation_type == 'belongsTo':
            relation_decorator = f"@belongsTo(() => {related_model}"
            if foreign_key:
                relation_decorator += f", {{keyTo: '{foreign_key}'}}"
            relation_decorator += ")"
        
        ts_model += f"  {relation_decorator}\n"
        ts_model += f"  {rel_name}: {related_model}[];\n\n"
    
    ts_model += f"  constructor(data?: Partial<{model_name}>) {{\n"
    ts_model += f"    super(data);\n"
    ts_model += f"  }}\n"
    ts_model += f"}}\n\n"
    
    ts_model += f"export interface {model_name}Relations {{\n"
    ts_model += f"  // describe navigational properties here\n"
    ts_model += f"}}\n"
    
    ts_model += f"export type {model_name}WithRelations = {model_name} & {model_name}Relations;\n"
    
    return ts_model

# Re-run the conversion process
converted_models = {}
for model_file in model_files:
    if model_file.endswith('.json'):
        model_json_path = os.path.join(lb3_models_path, model_file)
        with open(model_json_path, 'r') as f:
            model_content = json.load(f)
        
        converted_models[model_file] = convert_lb3_to_lb4(model_content)

# Save the converted models to files
output_dir = '/mnt/data/LB4_models/'
os.makedirs(output_dir, exist_ok=True)
for model_file, ts_model in converted_models.items():
    model_name = model_file.replace('.json', '.model.ts')
    output_path = os.path.join(output_dir, model_name)
    with open(output_path, 'w') as f:
        f.write(ts_model)

# List the generated files
os.listdir(output_dir)