Policies (Filters)

Guard your methods
Policies gives you the ability to apply arguments check on a function with zero effort.
SugoiJS provides policy which can be use for guarding any method.
The Policies are used by two simple steps:
Decorate your verification method with - @Policy(policyId?:string)
This decorator registers the function as "policy validator", this will later be used as guardian middleware.
policyId?: string - This ID will be used as an alias for calling this function, default is ${class name}.${function name}
Example
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 @Policy() //register this function as policy using the class name and function name, same as use @Policy("myNumberValidation")
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    static myNumberValidation(
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    policyData:{functionArgs: any[], 
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    policyMeta: Array<{argIndexToValidate:number,maxValue:number}>
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    }): true|any{
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​
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        // Those are the meta data values 
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        // which passed into the decorator itself while using @UsePolicy()
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        const argIndexToValidate = policyMeta[0].argIndexToValidate;
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        const maxValue = policyMeta[0].maxValue;
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​
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        if(policyData.functionArgs[argIndexToValidate] < maxValue){
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            return true; //Is valid, continue to the function/next policy or middleware
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        }else{
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            return policyData.functionArgs[argToValidate]; // so we will be able to identify the issue on the exception
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        }
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    }
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2. @UsePolicy(policy: TPolicy|string, failedResponseCode: number = 400, ...policyMeta: any[])
This decorator sets a policy guard on the function it decorates:
policy:TPolicy| string - For setting the referenced policy, use the policy ID from the previous section or anonymous function reference.
failedResponseCode: number - The code will be stored under the exception if the value does not meet the criteria.
policyMeta: any[] - Any further payload data which should pass to the policy.
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​
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/**
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* Apply policy by anonymous function
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* only numbers lower than 5 will log
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**/
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@UsePolicy((myNumber: number)=> myNumber < 5)
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lowerThan5NumberLogger(myNumber){
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    console.log(`number is lower the 5! ${myNumber}`);
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}
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Build your own policies:
Policy can be any function of type TPolicy
TPolicy = (policyData?:{functionArgs: any[], policyMeta: any[]})=>(Promise < (true|any) > | (true|any))
When the result is boolean, true means that the data is valid, all other values will be shown on the exception
Policy full example:
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class Validators{
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​
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    @Policy() //register this function as policy using the class name and function name, same as use @Policy("Validators.myNumberValidation")
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    static myNumberValidation(policyData:{functionArgs: any[], policyMeta: {argIndexToValidate:number,maxValue:number}[]}): true|any{
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        const myMeta = policyMeta[0];
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        //those are the meta data values which passed to the decorator itself while using @UsePolicy()
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        const argIndexToValidate = myMeta.argIndexToValidate;
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        const maxValue = myMeta.maxValue;
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​
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        if(policyData.functionArgs[argIndexToValidate] < maxValue){
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            return true; //Is valid, continue to the function/next policy
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        }else{
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            return policyData.functionArgs[argToValidate]; //so we will be able to identify the issue on the exception
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        }
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    }
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}
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​
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@UsePolicy("Validators.myNumberValidation",{argIndexToValidate:0,maxValue:5})
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lowerThan5NumberLogger(myNumber){
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    console.log(`number is lower the 5! ${myNumber}`);
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}
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Pre-defined polices

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Guard your methods

Decorate your verification method with - @Policy(policyId?:string)