// SPDX-FileCopyrightText: Copyright 2015-2025 go-swagger maintainers
// SPDX-License-Identifier: Apache-2.0

package security

import (
	"context"
	"net/http"
	"strings"

	"github.com/go-openapi/errors"

	"github.com/go-openapi/runtime"
)

const (
	query            = "query"
	header           = "header"
	accessTokenParam = "access_token"
)

// HTTPAuthenticator is a function that authenticates a HTTP request.
func HTTPAuthenticator(handler func(*http.Request) (bool, any, error)) runtime.Authenticator {
	return runtime.AuthenticatorFunc(func(params any) (bool, any, error) {
		if request, ok := params.(*http.Request); ok {
			return handler(request)
		}
		if scoped, ok := params.(*ScopedAuthRequest); ok {
			return handler(scoped.Request)
		}
		return false, nil, nil
	})
}

// HttpAuthenticator aliases [HTTPAuthenticator] for backward-compatibility.
//
// Deprecated: use [HTTPAuthenticator] instead.
func HttpAuthenticator(handler func(*http.Request) (bool, any, error)) runtime.Authenticator { //nolint:revive
	return HTTPAuthenticator(handler)
}

// ScopedAuthenticator is a function that authenticates an [http.Request] against a list of valid scopes.
func ScopedAuthenticator(handler func(*ScopedAuthRequest) (bool, any, error)) runtime.Authenticator {
	return runtime.AuthenticatorFunc(func(params any) (bool, any, error) {
		if request, ok := params.(*ScopedAuthRequest); ok {
			return handler(request)
		}
		return false, nil, nil
	})
}

// UserPassAuthentication validates a basic-auth credential.
//
// Implementations comparing the password (or any derived secret) against a
// known value MUST use [crypto/subtle.ConstantTimeCompare]: the runtime
// extracts the credential from the request and delegates the comparison
// here, and does not enforce a constant-time posture on the caller's behalf.
type UserPassAuthentication func(string, string) (any, error)

// UserPassAuthenticationCtx is the [context.Context]-aware variant of
// [UserPassAuthentication]. The same constant-time-comparison guidance
// applies.
type UserPassAuthenticationCtx func(context.Context, string, string) (context.Context, any, error)

// TokenAuthentication validates an API-key token.
//
// Implementations comparing the token against a known value MUST use
// [crypto/subtle.ConstantTimeCompare]; the runtime delegates the comparison
// here and does not enforce a constant-time posture on the caller's behalf.
type TokenAuthentication func(string) (any, error)

// TokenAuthenticationCtx is the [context.Context]-aware variant of
// [TokenAuthentication]. The same constant-time-comparison guidance
// applies.
type TokenAuthenticationCtx func(context.Context, string) (context.Context, any, error)

// ScopedTokenAuthentication validates a bearer/OAuth2 token along with the
// scopes required for the operation.
//
// Implementations comparing the token against a known value MUST use
// [crypto/subtle.ConstantTimeCompare]; the runtime delegates the comparison
// here and does not enforce a constant-time posture on the caller's behalf.
type ScopedTokenAuthentication func(string, []string) (any, error)

// ScopedTokenAuthenticationCtx is the [context.Context]-aware variant of
// [ScopedTokenAuthentication]. The same constant-time-comparison guidance
// applies.
type ScopedTokenAuthenticationCtx func(context.Context, string, []string) (context.Context, any, error)

var DefaultRealmName = "API"

type secCtxKey uint8

const (
	failedBasicAuth secCtxKey = iota
	oauth2SchemeName
)

func FailedBasicAuth(r *http.Request) string {
	return FailedBasicAuthCtx(r.Context())
}

func FailedBasicAuthCtx(ctx context.Context) string {
	v, ok := ctx.Value(failedBasicAuth).(string)
	if !ok {
		return ""
	}
	return v
}

func OAuth2SchemeName(r *http.Request) string {
	return OAuth2SchemeNameCtx(r.Context())
}

func OAuth2SchemeNameCtx(ctx context.Context) string {
	v, ok := ctx.Value(oauth2SchemeName).(string)
	if !ok {
		return ""
	}
	return v
}

// BasicAuth creates a basic auth authenticator with the provided authentication function.
func BasicAuth(authenticate UserPassAuthentication) runtime.Authenticator {
	return BasicAuthRealm(DefaultRealmName, authenticate)
}

// BasicAuthRealm creates a basic auth authenticator with the provided authentication function and realm name.
func BasicAuthRealm(realm string, authenticate UserPassAuthentication) runtime.Authenticator {
	if realm == "" {
		realm = DefaultRealmName
	}

	return HttpAuthenticator(func(r *http.Request) (bool, any, error) {
		if usr, pass, ok := r.BasicAuth(); ok {
			p, err := authenticate(usr, pass)
			if err != nil {
				*r = *r.WithContext(context.WithValue(r.Context(), failedBasicAuth, realm))
			}
			return true, p, err
		}
		*r = *r.WithContext(context.WithValue(r.Context(), failedBasicAuth, realm))
		return false, nil, nil
	})
}

// BasicAuthCtx creates a basic auth authenticator with the provided authentication function with support for [context.Context].
func BasicAuthCtx(authenticate UserPassAuthenticationCtx) runtime.Authenticator {
	return BasicAuthRealmCtx(DefaultRealmName, authenticate)
}

// BasicAuthRealmCtx creates a basic auth authenticator with the provided authentication function and realm name with support for [context.Context].
func BasicAuthRealmCtx(realm string, authenticate UserPassAuthenticationCtx) runtime.Authenticator {
	if realm == "" {
		realm = DefaultRealmName
	}

	return HttpAuthenticator(func(r *http.Request) (bool, any, error) {
		if usr, pass, ok := r.BasicAuth(); ok {
			ctx, p, err := authenticate(r.Context(), usr, pass)
			if err != nil {
				ctx = context.WithValue(ctx, failedBasicAuth, realm)
			}
			*r = *r.WithContext(ctx)
			return true, p, err
		}
		*r = *r.WithContext(context.WithValue(r.Context(), failedBasicAuth, realm))
		return false, nil, nil
	})
}

// APIKeyAuth creates an authenticator that uses a token for authorization.
// This token can be obtained from either a header or a query string.
func APIKeyAuth(name, in string, authenticate TokenAuthentication) runtime.Authenticator {
	inl := strings.ToLower(in)
	if inl != query && inl != header {
		// panic because this is most likely a typo
		panic(errors.New(http.StatusInternalServerError, "api key auth: in value needs to be either \"query\" or \"header\""))
	}

	var getToken func(*http.Request) string
	switch inl {
	case header:
		getToken = func(r *http.Request) string { return r.Header.Get(name) }
	case query:
		getToken = func(r *http.Request) string { return r.URL.Query().Get(name) }
	}

	return HttpAuthenticator(func(r *http.Request) (bool, any, error) {
		token := getToken(r)
		if token == "" {
			return false, nil, nil
		}

		p, err := authenticate(token)
		return true, p, err
	})
}

// APIKeyAuthCtx creates an authenticator that uses a token for authorization with support for [context.Context].
// This token can be obtained from either a header or a query string.
func APIKeyAuthCtx(name, in string, authenticate TokenAuthenticationCtx) runtime.Authenticator {
	inl := strings.ToLower(in)
	if inl != query && inl != header {
		// panic because this is most likely a typo
		panic(errors.New(http.StatusInternalServerError, "api key auth: in value needs to be either \"query\" or \"header\""))
	}

	var getToken func(*http.Request) string
	switch inl {
	case header:
		getToken = func(r *http.Request) string { return r.Header.Get(name) }
	case query:
		getToken = func(r *http.Request) string { return r.URL.Query().Get(name) }
	}

	return HttpAuthenticator(func(r *http.Request) (bool, any, error) {
		token := getToken(r)
		if token == "" {
			return false, nil, nil
		}

		ctx, p, err := authenticate(r.Context(), token)
		*r = *r.WithContext(ctx)
		return true, p, err
	})
}

// ScopedAuthRequest contains both the [http.Request] and the required scopes for a particular operation.
type ScopedAuthRequest struct {
	Request        *http.Request
	RequiredScopes []string
}

// BearerAuth for use with oauth2 flows.
func BearerAuth(name string, authenticate ScopedTokenAuthentication) runtime.Authenticator {
	const prefix = "Bearer "
	return ScopedAuthenticator(func(r *ScopedAuthRequest) (bool, any, error) {
		var token string
		hdr := r.Request.Header.Get(runtime.HeaderAuthorization)
		if after, ok := strings.CutPrefix(hdr, prefix); ok {
			token = after
		}
		if token == "" {
			qs := r.Request.URL.Query()
			token = qs.Get(accessTokenParam)
		}
		//#nosec
		ct, _, _ := runtime.ContentType(r.Request.Header)
		if token == "" && (ct == "application/x-www-form-urlencoded" || ct == "multipart/form-data") {
			token = r.Request.FormValue(accessTokenParam)
		}

		if token == "" {
			return false, nil, nil
		}

		rctx := context.WithValue(r.Request.Context(), oauth2SchemeName, name)
		*r.Request = *r.Request.WithContext(rctx)
		p, err := authenticate(token, r.RequiredScopes)
		return true, p, err
	})
}

// BearerAuthCtx for use with oauth2 flows with support for [context.Context].
func BearerAuthCtx(name string, authenticate ScopedTokenAuthenticationCtx) runtime.Authenticator {
	const prefix = "Bearer "
	return ScopedAuthenticator(func(r *ScopedAuthRequest) (bool, any, error) {
		var token string
		hdr := r.Request.Header.Get(runtime.HeaderAuthorization)
		if after, ok := strings.CutPrefix(hdr, prefix); ok {
			token = after
		}
		if token == "" {
			qs := r.Request.URL.Query()
			token = qs.Get(accessTokenParam)
		}
		//#nosec
		ct, _, _ := runtime.ContentType(r.Request.Header)
		if token == "" && (ct == "application/x-www-form-urlencoded" || ct == "multipart/form-data") {
			token = r.Request.FormValue(accessTokenParam)
		}

		if token == "" {
			return false, nil, nil
		}

		rctx := context.WithValue(r.Request.Context(), oauth2SchemeName, name)
		ctx, p, err := authenticate(rctx, token, r.RequiredScopes)
		*r.Request = *r.Request.WithContext(ctx)
		return true, p, err
	})
}