// Copyright 2019 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package resource

import (
	"context"

	"github.com/gohugoio/hugo/common/maps"
	"github.com/gohugoio/hugo/common/types"
	"github.com/gohugoio/hugo/langs"
	"github.com/gohugoio/hugo/media"

	"github.com/gohugoio/hugo/common/hugio"
)

var (
	_ ResourceDataProvider = (*resourceError)(nil)
	_ ResourceError        = (*resourceError)(nil)
)

// Cloner is for internal use.
type Cloner interface {
	Clone() Resource
}

// OriginProvider provides the original Resource if this is wrapped.
// This is an internal Hugo interface and not meant for use in the templates.
type OriginProvider interface {
	Origin() Resource
	GetFieldString(pattern string) (string, bool)
}

// NewResourceError creates a new ResourceError.
func NewResourceError(err error, data any) ResourceError {
	return &resourceError{
		error: err,
		data:  data,
	}
}

type resourceError struct {
	error
	data any
}

// The data associated with this error.
func (e *resourceError) Data() any {
	return e.data
}

// ResourceError is the error return from .Err in Resource in error situations.
type ResourceError interface {
	error
	ResourceDataProvider
}

// ErrProvider provides an Err.
type ErrProvider interface {
	// Err returns an error if this resource is in an error state.
	// This will currently only be set for resources obtained from resources.GetRemote.
	Err() ResourceError
}

// Resource represents a linkable resource, i.e. a content page, image etc.
type Resource interface {
	ResourceWithoutMeta
	ResourceMetaProvider
}

type ResourceWithoutMeta interface {
	ResourceTypeProvider
	MediaTypeProvider
	ResourceLinksProvider
	ResourceDataProvider
	ErrProvider
}

type ResourceWrapper interface {
	UnwrappedResource() Resource
	WrapResource(Resource) ResourceWrapper
}

type ResourceTypeProvider interface {
	// ResourceType is the resource type. For most file types, this is the main
	// part of the MIME type, e.g. "image", "application", "text" etc.
	// For content pages, this value is "page".
	ResourceType() string
}

type ResourceTypesProvider interface {
	ResourceTypeProvider
	MediaTypeProvider
}

type MediaTypeProvider interface {
	// MediaType is this resource's MIME type.
	MediaType() media.Type
}

type ResourceLinksProvider interface {
	// Permalink represents the absolute link to this resource.
	Permalink() string

	// RelPermalink represents the host relative link to this resource.
	RelPermalink() string
}

// ResourceMetaProvider provides metadata about a resource.
type ResourceMetaProvider interface {
	ResourceNameTitleProvider
	ResourceParamsProvider
}

type WithResourceMetaProvider interface {
	// WithResourceMeta creates a new Resource with the given metadata.
	// For internal use.
	WithResourceMeta(ResourceMetaProvider) Resource
}

type ResourceNameTitleProvider interface {
	// Name is the logical name of this resource. This can be set in the front matter
	// metadata for this resource. If not set, Hugo will assign a value.
	// This will in most cases be the base filename.
	// So, for the image "/some/path/sunset.jpg" this will be "sunset.jpg".
	// The value returned by this method will be used in the GetByPrefix and ByPrefix methods
	// on Resources.
	Name() string

	// Title returns the title if set in front matter. For content pages, this will be the expected value.
	Title() string
}

type NameNormalizedProvider interface {
	// NameNormalized is the normalized name of this resource.
	// For internal use (for now).
	NameNormalized() string
}

type ResourceParamsProvider interface {
	// Params set in front matter for this resource.
	Params() maps.Params
}

type ResourceDataProvider interface {
	// Resource specific data set by Hugo.
	// One example would be .Data.Integrity for fingerprinted resources.
	Data() any
}

// ResourcesLanguageMerger describes an interface for merging resources from a
// different language.
type ResourcesLanguageMerger interface {
	MergeByLanguage(other Resources) Resources

	// Needed for integration with the tpl package.
	// For internal use.
	MergeByLanguageInterface(other any) (any, error)
}

// Identifier identifies a resource.
type Identifier interface {
	// Key is is mostly for internal use and should be considered opaque.
	// This value may change between Hugo versions.
	Key() string
}

// WeightProvider provides a weight.
type WeightProvider interface {
	Weight() int
}

// Weight0Provider provides a weight that's considered before the WeightProvider in sorting.
// This allows the weight set on a given term to win.
type Weight0Provider interface {
	Weight0() int
}

// ContentResource represents a Resource that provides a way to get to its content.
// Most Resource types in Hugo implements this interface, including Page.
type ContentResource interface {
	MediaType() media.Type
	ContentProvider
}

// ContentProvider provides Content.
// This should be used with care, as it will read the file content into memory, but it
// should be cached as effectively as possible by the implementation.
type ContentProvider interface {
	// Content returns this resource's content. It will be equivalent to reading the content
	// that RelPermalink points to in the published folder.
	// The return type will be contextual, and should be what you would expect:
	// * Page: template.HTML
	// * JSON: String
	// * Etc.
	Content(context.Context) (any, error)
}

// ReadSeekCloserResource is a Resource that supports loading its content.
type ReadSeekCloserResource interface {
	MediaType() media.Type
	hugio.ReadSeekCloserProvider
}

// LengthProvider is a Resource that provides a length
// (typically the length of the content).
type LengthProvider interface {
	Len(context.Context) int
}

// LanguageProvider is a Resource in a language.
type LanguageProvider interface {
	Language() *langs.Language
}

// TranslationKeyProvider connects translations of the same Resource.
type TranslationKeyProvider interface {
	TranslationKey() string
}

// Staler controls stale state of a Resource. A stale resource should be discarded.
type Staler interface {
	StaleMarker
	StaleInfo
}

// StaleMarker marks a Resource as stale.
type StaleMarker interface {
	MarkStale()
}

// StaleInfo tells if a resource is marked as stale.
type StaleInfo interface {
	StaleVersion() uint32
}

// StaleVersion returns the StaleVersion for the given os,
// or 0 if not set.
func StaleVersion(os any) uint32 {
	if s, ok := os.(StaleInfo); ok {
		return s.StaleVersion()
	}
	return 0
}

// StaleVersionSum calculates the sum of the StaleVersionSum for the given oss.
func StaleVersionSum(oss ...any) uint32 {
	var version uint32
	for _, o := range oss {
		if s, ok := o.(StaleInfo); ok && s.StaleVersion() > 0 {
			version += s.StaleVersion()
		}
	}
	return version
}

// MarkStale will mark any of the oses as stale, if possible.
func MarkStale(os ...any) {
	for _, o := range os {
		if types.IsNil(o) {
			continue
		}
		if s, ok := o.(StaleMarker); ok {
			s.MarkStale()
		}
	}
}

// UnmarshableResource represents a Resource that can be unmarshaled to some other format.
type UnmarshableResource interface {
	ReadSeekCloserResource
	Identifier
}

type resourceTypesHolder struct {
	mediaType    media.Type
	resourceType string
}

func (r resourceTypesHolder) MediaType() media.Type {
	return r.mediaType
}

func (r resourceTypesHolder) ResourceType() string {
	return r.resourceType
}

func NewResourceTypesProvider(mediaType media.Type, resourceType string) ResourceTypesProvider {
	return resourceTypesHolder{mediaType: mediaType, resourceType: resourceType}
}