// Copyright (c) The OpenTofu Authors
// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0

package regaddr

import (
	"fmt"
	"strings"

	"github.com/opentofu/svchost"
	"golang.org/x/net/idna"
)

// Provider encapsulates a single provider type. In the future this will be
// extended to include additional fields including Namespace and SourceHost
type Provider struct {
	Type      string
	Namespace string
	Hostname  svchost.Hostname
}

// DefaultProviderRegistryHost is the hostname used for provider addresses that do
// not have an explicit hostname.
const DefaultProviderRegistryHost = svchost.Hostname("registry.opentofu.org")

// TransitionalDefaultProviderRegistryHost is the default registry hostname used
// by OpenTofu's predecessor.
//
// Addresses with this hostname are not typically used directly with OpenTofu,
// but OpenTofu contains some support code to help with automatically migrating
// certain uses of this hostname to use [DefaultProviderRegistryHost] instead.
const TransitionalDefaultProviderRegistryHost = svchost.Hostname("registry.terraform.io")

// BuiltInProviderHost is a hostname currently reserved for potential future
// use to represent built-in providers that are OpenTofu-specific, rather
// than inherited from OpenTofu's predecessor.
//
// To determine whether a particular provider address should be treated as
// built-in, prefer to use [Provider.IsBuiltIn] instead of directly comparing
// to this value, because [TransitionalBuiltInProviderHost] is also a valid
// hostname for certain built-in providers.
const BuiltInProviderHost = svchost.Hostname("opentofu.org")

// TransitionalBuiltInProviderHost is a hostname used for the namespace of
// "built-in" providers inherited from OpenTofu's predecessor.
// Built-in provider addresses must also have their namespace set
// to BuiltInProviderNamespace in order to be considered as built-in.
const TransitionalBuiltInProviderHost = svchost.Hostname("terraform.io")

// BuiltInProviderNamespace is the provider namespace used for "built-in"
// providers. Built-in provider addresses must also have their hostname
// set to BuiltInProviderHost in order to be considered as built-in.
//
// The this namespace is literally named "builtin", in the hope that users
// who see FQNs containing this will be able to infer the way in which they are
// special, even if they haven't encountered the concept formally yet.
const BuiltInProviderNamespace = "builtin"

// UnknownProviderNamespace is the special string used to indicate
// unknown namespace, e.g. in "aws". This is equivalent to
// LegacyProviderNamespace for <0.12 style address. This namespace
// would never be produced by OpenTofu itself explicitly, since it is
// only an internal placeholder.
const UnknownProviderNamespace = "?"

// LegacyProviderNamespace is the special string used in the Namespace field
// of type Provider to mark a legacy provider address. This special namespace
// value would normally be invalid, and can be used only when the hostname is
// DefaultProviderRegistryHost because that host owns the mapping from legacy
// name to FQN. This is produced only by historical versions of OpenTofu's
// predecessor.
const LegacyProviderNamespace = "-"

// String returns an FQN string, indended for use in machine-readable output.
func (pt Provider) String() string {
	if pt.IsZero() {
		panic("called String on zero-value addrs.Provider")
	}
	return pt.Hostname.ForDisplay() + "/" + pt.Namespace + "/" + pt.Type
}

// ForDisplay returns a user-friendly FQN string, simplified for readability. If
// the provider is using the default hostname, the hostname is omitted.
func (pt Provider) ForDisplay() string {
	if pt.IsZero() {
		panic("called ForDisplay on zero-value addrs.Provider")
	}

	if pt.Hostname == DefaultProviderRegistryHost {
		return pt.Namespace + "/" + pt.Type
	}
	return pt.Hostname.ForDisplay() + "/" + pt.Namespace + "/" + pt.Type
}

// NewProvider constructs a provider address from its parts, and normalizes
// the namespace and type parts to lowercase using unicode case folding rules
// so that resulting addrs.Provider values can be compared using standard
// Go equality rules (==).
//
// The hostname is given as a svchost.Hostname, which is required by the
// contract of that type to have already been normalized for equality testing.
//
// This function will panic if the given namespace or type name are not valid.
// When accepting namespace or type values from outside the program, use
// ParseProviderPart first to check that the given value is valid.
func NewProvider(hostname svchost.Hostname, namespace, typeName string) Provider {
	if namespace == LegacyProviderNamespace {
		// Legacy provider addresses must always be created via struct
		panic("attempt to create legacy provider address using NewProvider; use Provider{} instead")
	}
	if namespace == UnknownProviderNamespace {
		// Provider addresses with unknown namespace must always
		// be created via struct
		panic("attempt to create provider address with unknown namespace using NewProvider; use Provider{} instead")
	}
	if namespace == "" {
		// This case is already handled by MustParseProviderPart() below,
		// but we catch it early to provide more helpful message.
		panic("attempt to create provider address with empty namespace")
	}

	return Provider{
		Type:      MustParseProviderPart(typeName),
		Namespace: MustParseProviderPart(namespace),
		Hostname:  hostname,
	}
}

// LegacyString returns the provider type, which is frequently used
// interchangeably with provider name. This function can and should be removed
// when provider type is fully integrated. As a safeguard for future
// refactoring, this function panics if the Provider is not a legacy provider.
func (pt Provider) LegacyString() string {
	if pt.IsZero() {
		panic("called LegacyString on zero-value addrs.Provider")
	}
	if pt.Namespace != LegacyProviderNamespace && pt.Namespace != BuiltInProviderNamespace {
		panic(pt.String() + " cannot be represented as a legacy string")
	}
	return pt.Type
}

// IsZero returns true if the receiver is the zero value of addrs.Provider.
//
// The zero value is not a valid addrs.Provider and calling other methods on
// such a value is likely to either panic or otherwise misbehave.
func (pt Provider) IsZero() bool {
	return pt == Provider{}
}

// HasKnownNamespace returns true if the provider namespace is known
// (also if it is legacy namespace)
func (pt Provider) HasKnownNamespace() bool {
	return pt.Namespace != UnknownProviderNamespace
}

// IsBuiltIn returns true if the receiver is the address of a "built-in"
// provider. That is, a provider under that is included as part of the OpenTofu
// CLI executable itself rather than one to be installed from elsewhere.
//
// These are ignored by the OpenTofu provider installer because they are assumed
// to already be available without any further installation.
func (pt Provider) IsBuiltIn() bool {
	return (pt.Hostname == TransitionalBuiltInProviderHost || pt.Hostname == BuiltInProviderHost) && pt.Namespace == BuiltInProviderNamespace
}

// LessThan returns true if the receiver should sort before the other given
// address in an ordered list of provider addresses.
//
// This ordering is an arbitrary one just to allow deterministic results from
// functions that would otherwise have no natural ordering. It's subject
// to change in the future.
func (pt Provider) LessThan(other Provider) bool {
	switch {
	case pt.Hostname != other.Hostname:
		return pt.Hostname < other.Hostname
	case pt.Namespace != other.Namespace:
		return pt.Namespace < other.Namespace
	default:
		return pt.Type < other.Type
	}
}

// IsLegacy returns true if the provider is a legacy-style provider
func (pt Provider) IsLegacy() bool {
	if pt.IsZero() {
		panic("called IsLegacy() on zero-value addrs.Provider")
	}

	return pt.Hostname == DefaultProviderRegistryHost && pt.Namespace == LegacyProviderNamespace

}

// Equals returns true if the receiver and other provider have the same attributes.
func (pt Provider) Equals(other Provider) bool {
	return pt == other
}

// ParseProviderSource parses the source attribute and returns a provider.
//
// The following are valid source string formats:
//
//	name
//	namespace/name
//	hostname/namespace/name
//
// "name"-only format is parsed as -/name (i.e. legacy namespace)
// requiring further identification of the namespace via Registry API
func ParseProviderSource(str string) (Provider, error) {
	var ret Provider
	parts, err := parseSourceStringParts(str)
	if err != nil {
		return ret, err
	}

	name := parts[len(parts)-1]
	ret.Type = name
	ret.Hostname = DefaultProviderRegistryHost

	if len(parts) == 1 {
		return Provider{
			Hostname:  DefaultProviderRegistryHost,
			Namespace: UnknownProviderNamespace,
			Type:      name,
		}, nil
	}

	if len(parts) >= 2 {
		// the namespace is always the second-to-last part
		givenNamespace := parts[len(parts)-2]
		if givenNamespace == LegacyProviderNamespace {
			// For now we're tolerating legacy provider addresses until we've
			// finished updating the rest of the codebase to no longer use them,
			// or else we'd get errors round-tripping through legacy subsystems.
			ret.Namespace = LegacyProviderNamespace
		} else {
			namespace, err := ParseProviderPart(givenNamespace)
			if err != nil {
				return Provider{}, &ParserError{
					Summary: "Invalid provider namespace",
					Detail:  fmt.Sprintf(`Invalid provider namespace %q in source %q: %s"`, namespace, str, err),
				}
			}
			ret.Namespace = namespace
		}
	}

	// Final Case: 3 parts
	if len(parts) == 3 {
		// the namespace is always the first part in a three-part source string
		hn, err := svchost.ForComparison(parts[0])
		if err != nil {
			return Provider{}, &ParserError{
				Summary: "Invalid provider source hostname",
				Detail:  fmt.Sprintf(`Invalid provider source hostname namespace %q in source %q: %s"`, hn, str, err),
			}
		}
		ret.Hostname = hn
	}

	if ret.Namespace == LegacyProviderNamespace && ret.Hostname != DefaultProviderRegistryHost {
		// Legacy provider addresses must always be on the default registry
		// host, because the default registry host decides what actual FQN
		// each one maps to.
		return Provider{}, &ParserError{
			Summary: "Invalid provider namespace",
			Detail:  "The legacy provider namespace \"-\" can be used only with hostname " + DefaultProviderRegistryHost.ForDisplay() + ".",
		}
	}

	// Due to how plugin executables are named and provider git repositories
	// are conventionally named, it's a reasonable and
	// apparently-somewhat-common user error to incorrectly use the
	// "terraform-provider-" prefix in a provider source address. There is
	// no good reason for a provider to have the prefix "terraform-" anyway,
	// so we've made that invalid from the start both so we can give feedback
	// to provider developers about the terraform- prefix being redundant
	// and give specialized feedback to folks who incorrectly use the full
	// terraform-provider- prefix to help them self-correct.
	const redundantPrefix = "opentofu-"
	const userErrorPrefix = "opentofu-provider-"
	const transitionalRedundantPrefix = "terraform-"
	const transitionalUserErrorPrefix = "terraform-provider-"
	if strings.HasPrefix(ret.Type, transitionalRedundantPrefix) {
		if strings.HasPrefix(ret.Type, transitionalUserErrorPrefix) {
			// Likely user error. We only return this specialized error if
			// whatever is after the prefix would otherwise be a
			// syntactically-valid provider type, so we don't end up advising
			// the user to try something that would be invalid for another
			// reason anyway.
			// (This is mainly just for robustness, because the validation
			// we already did above should've rejected most/all ways for
			// the suggestedType to end up invalid here.)
			suggestedType := ret.Type[len(transitionalUserErrorPrefix):]
			if _, err := ParseProviderPart(suggestedType); err == nil {
				suggestedAddr := ret
				suggestedAddr.Type = suggestedType
				return Provider{}, &ParserError{
					Summary: "Invalid provider type",
					Detail:  fmt.Sprintf("Provider source %q has a type with the prefix %q, which isn't valid. Although that prefix is often used in the names of version control repositories for Terraform providers, provider source strings should not include it.\n\nDid you mean %q?", ret.ForDisplay(), transitionalUserErrorPrefix, suggestedAddr.ForDisplay()),
				}
			}
		}
		// Otherwise, probably instead an incorrectly-named provider, perhaps
		// arising from a similar instinct to what causes there to be
		// thousands of Python packages on PyPI with "python-"-prefixed
		// names.
		return Provider{}, &ParserError{
			Summary: "Invalid provider type",
			Detail:  fmt.Sprintf("Provider source %q has a type with the prefix %q, which isn't allowed because it would be redundant to name a Terraform provider with that prefix. If you are the author of this provider, rename it to not include the prefix.", ret, transitionalRedundantPrefix),
		}
	} else if strings.HasPrefix(ret.Type, redundantPrefix) {
		// This is the same as above but for the OpenTofu-flavored versions
		// of these names.
		if strings.HasPrefix(ret.Type, userErrorPrefix) {
			suggestedType := ret.Type[len(userErrorPrefix):]
			if _, err := ParseProviderPart(suggestedType); err == nil {
				suggestedAddr := ret
				suggestedAddr.Type = suggestedType
				return Provider{}, &ParserError{
					Summary: "Invalid provider type",
					Detail:  fmt.Sprintf("Provider source %q has a type with the prefix %q, which isn't valid. Although that prefix is sometimes used in the names of version control repositories for OpenTofu providers, provider source strings should not include it.\n\nDid you mean %q?", ret.ForDisplay(), userErrorPrefix, suggestedAddr.ForDisplay()),
				}
			}
		}
		return Provider{}, &ParserError{
			Summary: "Invalid provider type",
			Detail:  fmt.Sprintf("Provider source %q has a type with the prefix %q, which isn't allowed because it would be redundant to name an OpenTofu provider with that prefix. If you are the author of this provider, rename it to not include the prefix.", ret, redundantPrefix),
		}
	}

	return ret, nil
}

// MustParseProviderSource is a wrapper around ParseProviderSource that panics if
// it returns an error.
func MustParseProviderSource(raw string) Provider {
	p, err := ParseProviderSource(raw)
	if err != nil {
		panic(err)
	}
	return p
}

// ValidateProviderAddress returns error if the given address is not FQN,
// that is if it is missing any of the three components from
// hostname/namespace/name.
func ValidateProviderAddress(raw string) error {
	parts, err := parseSourceStringParts(raw)
	if err != nil {
		return err
	}

	if len(parts) != 3 {
		return &ParserError{
			Summary: "Invalid provider address format",
			Detail:  `Expected FQN in the format "hostname/namespace/name"`,
		}
	}

	p, err := ParseProviderSource(raw)
	if err != nil {
		return err
	}

	if !p.HasKnownNamespace() {
		return &ParserError{
			Summary: "Unknown provider namespace",
			Detail:  `Expected FQN in the format "hostname/namespace/name"`,
		}
	}

	if !p.IsLegacy() {
		return &ParserError{
			Summary: "Invalid legacy provider namespace",
			Detail:  `Expected FQN in the format "hostname/namespace/name"`,
		}
	}

	return nil
}

func parseSourceStringParts(str string) ([]string, error) {
	// split the source string into individual components
	parts := strings.Split(str, "/")
	if len(parts) == 0 || len(parts) > 3 {
		return nil, &ParserError{
			Summary: "Invalid provider source string",
			Detail:  `The "source" attribute must be in the format "[hostname/][namespace/]name"`,
		}
	}

	// check for an invalid empty string in any part
	for i := range parts {
		if parts[i] == "" {
			return nil, &ParserError{
				Summary: "Invalid provider source string",
				Detail:  `The "source" attribute must be in the format "[hostname/][namespace/]name"`,
			}
		}
	}

	// check the 'name' portion, which is always the last part
	givenName := parts[len(parts)-1]
	name, err := ParseProviderPart(givenName)
	if err != nil {
		return nil, &ParserError{
			Summary: "Invalid provider type",
			Detail:  fmt.Sprintf(`Invalid provider type %q in source %q: %s"`, givenName, str, err),
		}
	}
	parts[len(parts)-1] = name

	return parts, nil
}

// ParseProviderPart processes an addrs.Provider namespace or type string
// provided by an end-user, producing a normalized version if possible or
// an error if the string contains invalid characters.
//
// A provider part is processed in the same way as an individual label in a DNS
// domain name: it is transformed to lowercase per the usual DNS case mapping
// and normalization rules and may contain only letters, digits, and dashes.
// Additionally, dashes may not appear at the start or end of the string.
//
// These restrictions are intended to allow these names to appear in fussy
// contexts such as directory/file names on case-insensitive filesystems,
// repository names on GitHub, etc. We're using the DNS rules in particular,
// rather than some similar rules defined locally, because the hostname part
// of an addrs.Provider is already a hostname and it's ideal to use exactly
// the same case folding and normalization rules for all of the parts.
//
// In practice a provider type string conventionally does not contain dashes
// either. Such names are permitted, but providers with such type names will be
// hard to use because their resource type names will not be able to contain
// the provider type name and thus each resource will need an explicit provider
// address specified. (A real-world example of such a provider is the
// "google-beta" variant of the GCP provider, which has resource types that
// start with the "google_" prefix instead.)
//
// It's valid to pass the result of this function as the argument to a
// subsequent call, in which case the result will be identical.
func ParseProviderPart(given string) (string, error) {
	if len(given) == 0 {
		return "", fmt.Errorf("must have at least one character")
	}

	// We're going to process the given name using the same "IDNA" library we
	// use for the hostname portion, since it already implements the case
	// folding rules we want.
	//
	// The idna library doesn't expose individual label parsing directly, but
	// once we've verified it doesn't contain any dots we can just treat it
	// like a top-level domain for this library's purposes.
	if strings.ContainsRune(given, '.') {
		return "", fmt.Errorf("dots are not allowed")
	}

	// We don't allow names containing multiple consecutive dashes, just as
	// a matter of preference: they look weird, confusing, or incorrect.
	// This also, as a side-effect, prevents the use of the "punycode"
	// indicator prefix "xn--" that would cause the IDNA library to interpret
	// the given name as punycode, because that would be weird and unexpected.
	if strings.Contains(given, "--") {
		return "", fmt.Errorf("cannot use multiple consecutive dashes")
	}

	result, err := idna.Lookup.ToUnicode(given)
	if err != nil {
		return "", fmt.Errorf("must contain only letters, digits, and dashes, and may not use leading or trailing dashes")
	}

	return result, nil
}

// MustParseProviderPart is a wrapper around ParseProviderPart that panics if
// it returns an error.
func MustParseProviderPart(given string) string {
	result, err := ParseProviderPart(given)
	if err != nil {
		panic(err.Error())
	}
	return result
}
