// Copyright 2017 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package markup

import (
	"bytes"
	"io"
	"path"
	"strings"

	"code.gitea.io/gitea/modules/setting"
)

// Renderer defines an interface for rendering markup file to HTML
type Renderer interface {
	Name() string // markup format name
	Extensions() []string
	SanitizerRules() []setting.MarkupSanitizerRule
	Render(ctx *RenderContext, input io.Reader, output io.Writer) error
}

// PostProcessRenderer defines an interface for renderers who need post process
type PostProcessRenderer interface {
	NeedPostProcess() bool
}

// ExternalRenderer defines an interface for external renderers
type ExternalRenderer interface {
	// SanitizerDisabled disabled sanitize if return true
	SanitizerDisabled() bool

	// DisplayInIFrame represents whether render the content with an iframe
	DisplayInIFrame() bool
}

// RendererContentDetector detects if the content can be rendered
// by specified renderer
type RendererContentDetector interface {
	CanRender(filename string, input io.Reader) bool
}

var (
	extRenderers = make(map[string]Renderer)
	renderers    = make(map[string]Renderer)
)

// RegisterRenderer registers a new markup file renderer
func RegisterRenderer(renderer Renderer) {
	renderers[renderer.Name()] = renderer
	for _, ext := range renderer.Extensions() {
		extRenderers[strings.ToLower(ext)] = renderer
	}
}

// GetRendererByFileName get renderer by filename
func GetRendererByFileName(filename string) Renderer {
	extension := strings.ToLower(path.Ext(filename))
	return extRenderers[extension]
}

// DetectRendererType detects the markup type of the content
func DetectRendererType(filename string, input io.Reader) string {
	buf, err := io.ReadAll(input)
	if err != nil {
		return ""
	}
	for _, renderer := range renderers {
		if detector, ok := renderer.(RendererContentDetector); ok && detector.CanRender(filename, bytes.NewReader(buf)) {
			return renderer.Name()
		}
	}
	return ""
}

// DetectMarkupTypeByFileName returns the possible markup format type via the filename
func DetectMarkupTypeByFileName(filename string) string {
	if parser := GetRendererByFileName(filename); parser != nil {
		return parser.Name()
	}
	return ""
}

func PreviewableExtensions() []string {
	extensions := make([]string, 0, len(extRenderers))
	for extension := range extRenderers {
		extensions = append(extensions, extension)
	}
	return extensions
}