package getproviders

import (
	"fmt"

	svchost "github.com/hashicorp/terraform-svchost"
	disco "github.com/hashicorp/terraform-svchost/disco"

	"github.com/hashicorp/terraform/addrs"
)

// RegistrySource is a Source that knows how to find and install providers from
// their originating provider registries.
type RegistrySource struct {
	services *disco.Disco
}

// NewRegistrySource creates and returns a new source that will install
// providers from their originating provider registries.
func NewRegistrySource(services *disco.Disco) *RegistrySource {
	return &RegistrySource{
		services: services,
	}
}

// AvailableVersions returns all of the versions available for the provider
// with the given address, or an error if that result cannot be determined.
//
// If the request fails, the returned error might be an value of
// ErrHostNoProviders, ErrHostUnreachable, ErrUnauthenticated,
// ErrProviderNotKnown, or ErrQueryFailed. Callers must be defensive and
// expect errors of other types too, to allow for future expansion.
func (s *RegistrySource) AvailableVersions(provider addrs.Provider) (VersionList, error) {
	client, err := s.registryClient(provider.Hostname)
	if err != nil {
		return nil, err
	}

	versionStrs, err := client.ProviderVersions(provider)
	if err != nil {
		return nil, err
	}

	if len(versionStrs) == 0 {
		return nil, nil
	}

	ret := make(VersionList, len(versionStrs))
	for i, str := range versionStrs {
		v, err := ParseVersion(str)
		if err != nil {
			return nil, ErrQueryFailed{
				Provider: provider,
				Wrapped:  fmt.Errorf("registry response includes invalid version string %q: %s", str, err),
			}
		}
		ret[i] = v
	}
	ret.Sort() // lowest precedence first, preserving order when equal precedence
	return ret, nil
}

// DownloadLocation returns metadata about the location and capabilities of
// a distribution package for a particular provider at a particular version
// targeting a particular platform.
//
// Callers of DownloadLocation should first call AvailableVersions and pass
// one of the resulting versions to this function. This function cannot
// distinguish between a version that is not available and an unsupported
// target platform, so if it encounters either case it will return an error
// suggesting that the target platform isn't supported under the assumption
// that the caller already checked that the version is available at all.
//
// To find a package suitable for the platform where the provider installation
// process is running, set the "target" argument to
// findproviders.CurrentPlatform.
//
// If the request fails, the returned error might be an value of
// ErrHostNoProviders, ErrHostUnreachable, ErrUnauthenticated,
// ErrPlatformNotSupported, or ErrQueryFailed. Callers must be defensive and
// expect errors of other types too, to allow for future expansion.
func (s *RegistrySource) DownloadLocation(provider addrs.Provider, version Version, target Platform) (PackageMeta, error) {
	client, err := s.registryClient(provider.Hostname)
	if err != nil {
		return PackageMeta{}, err
	}

	return client.PackageMeta(provider, version, target)
}

func (s *RegistrySource) registryClient(hostname svchost.Hostname) (*registryClient, error) {
	host, err := s.services.Discover(hostname)
	if err != nil {
		return nil, ErrHostUnreachable{
			Hostname: hostname,
			Wrapped:  err,
		}
	}

	url, err := host.ServiceURL("providers.v1")
	switch err := err.(type) {
	case nil:
		// okay! We'll fall through and return below.
	case *disco.ErrServiceNotProvided:
		return nil, ErrHostNoProviders{
			Hostname: hostname,
		}
	case *disco.ErrVersionNotSupported:
		return nil, ErrHostNoProviders{
			Hostname:        hostname,
			HasOtherVersion: true,
		}
	default:
		return nil, ErrHostUnreachable{
			Hostname: hostname,
			Wrapped:  err,
		}
	}

	// Check if we have credentials configured for this hostname.
	creds, err := s.services.CredentialsForHost(hostname)
	if err != nil {
		// This indicates that a credentials helper failed, which means we
		// can't do anything better than just pass through the helper's
		// own error message.
		return nil, fmt.Errorf("failed to retrieve credentials for %s: %s", hostname, err)
	}

	return newRegistryClient(url, creds), nil
}