/* A Dispatcher is a collection of operations that do run-time
 * dispatch on the types of their arguments. Thus, every individual
 * method is like a typed-function (from the library by that name),
 * but they can depend on one another and on ona another's implementations
 * for specific types (including their own).
 */

// First helper types and functions for the Dispatcher

type TypeName = string
type Parameter = TypeName
type Signature = Parameter[]
type DependenciesType = Record<string, Function>

// A "canned" dependency for a builtin function:
export type typeOfDependency = {typeOf: (x: unknown) => TypeName}

// Utility needed in type definitions
//dummy implementation for now
export function joinTypes(a: TypeName, b: TypeName) {
   if (a === b) return a
   return 'any'
}

// Now types used in the Dispatcher class itself

type TypeSpecification = {
   before?: TypeName[],
   test: ((x: unknown) => boolean)
      | ((d: DependenciesType) => (x: unknown) => boolean),
   from: Record<TypeName, Function>,
   infer?: (d: DependenciesType) => (z: unknown) => TypeName
}

type SpecObject = Record<string, Function | TypeSpecification>
type SpecificationsGroup = Record<string, SpecObject>

export class Dispatcher {
   installSpecification(
      name: string,
      signature: Signature,
      returns: TypeName,
      dependencies: Record<string, Signature>,
      behavior: Function // possible todo: constrain this type based
      // on the signature, return type, and dependencies. Not sure if
      // that's really possible, though.
   ) {
      console.log('Pretending to install', name, signature, '=>', returns)
      //TODO: implement me
   }
   installType(name: TypeName, typespec: TypeSpecification) {
      console.log('Pretending to install type', name, typespec)
      //TODO: implement me
   }
   constructor(collection: SpecificationsGroup) { 
      for (const key in collection) {
         console.log('Working on', key)
         for (const identifier in collection[key]) {
            console.log('Handling', key, ':', identifier)
            const parts = identifier.split('_')
            if (parts[parts.length - 1] === 'type') {
               parts.pop()
               const name = parts.join('_')
               this.installType(
                  name, collection[key][identifier] as TypeSpecification)
            } else {
               const name = parts[0]
               this.installSpecification(
                  name, ['dunno'], 'unsure', {},
                  collection[key][identifier] as Function)
            }
         }
      }
   }
}