sourceafIoc::DependencyProviderSource.fan

**
** Contribute `DependencyProvider`s to provide your own dependencies for fields annotated with the 
** '@Inject' facet. Typically you would augment '@Inject' with your own facet to provide injection 
** meta. See [@ServiceId]`ServiceId` and [@Autobuild]`Autobuild` for builtin examples. 
** 
** pre>
** @Contribute
** static Void contributeDependencyProviderSource(OrderedConfig config) {
**   serviceIdProvider := config.autobuild(ServiceIdProvider#)
**   config.addUnordered(serviceIdProvider)
** }
** <pre
** 
const mixin DependencyProviderSource {
    
    internal abstract Obj? provideDependency(ProviderCtx proCtx, Type dependencyType)
    
}

internal const class DependencyProviderSourceImpl : DependencyProviderSource {
    private const DependencyProvider[] dependencyProviders

    new make(DependencyProvider[] dependencyProviders) {
        this.dependencyProviders = dependencyProviders.toImmutable
    }

    override Obj? provideDependency(ProviderCtx proCtx, Type dependencyType) {
        dps := dependencyProviders.findAll { it.canProvide(proCtx, dependencyType) }

        if (dps.isEmpty)
            return null
        
        if (dps.size > 1)
            throw IocErr(ServiceMessages.onlyOneDependencyProviderAllowed(dependencyType, dps.map { it.typeof }))
        
        dependency := dps[0].provide(proCtx, dependencyType)
        
        if (!dependency.typeof.fits(dependencyType))
            throw IocErr(ServiceMessages.dependencyDoesNotFit(dependency.typeof, dependencyType))

        return dependency
    }
}