// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
// Copyright 2024 WJQSERVER. All rights reserved.
// All rights reserved by WJQSERVER, related rights can be exercised by the infinite-iroha organization.
package webdav

import (
	"context"
	"encoding/xml"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"path"
	"strings"
	"sync"
	"time"

	"github.com/infinite-iroha/touka"
)

// FileSystem defines the interface for a file system to be served by the WebDAV handler.
// It provides methods for file and directory manipulation and information retrieval,
// abstracting the underlying storage from the WebDAV protocol logic.
type FileSystem interface {
	Mkdir(ctx context.Context, name string, perm os.FileMode) error
	OpenFile(c *touka.Context, name string, flag int, perm os.FileMode) (File, error)
	RemoveAll(ctx context.Context, name string) error
	Rename(ctx context.Context, oldName, newName string) error
	Stat(ctx context.Context, name string) (ObjectInfo, error)
}

// File defines the interface for a file-like object in the FileSystem.
// It embeds standard io interfaces for reading, writing, seeking, and closing,
// and adds methods for directory listing and metadata retrieval.
type File interface {
	io.Closer
	io.Reader
	io.Seeker
	io.Writer
	Readdir(count int) ([]ObjectInfo, error)
	Stat() (ObjectInfo, error)
}

// ObjectInfo provides a common interface for file and directory metadata.
// It is designed to be compatible with os.FileInfo to allow for easy integration
// with standard library functions, while providing an abstraction layer.
type ObjectInfo interface {
	Name() string
	Size() int64
	Mode() os.FileMode
	ModTime() time.Time
	IsDir() bool
	Sys() interface{} // Underlying data source (can be nil).
}

// Propfind represents the XML structure of a PROPFIND request body.
// It allows clients to request all properties (`Allprop`), a specific set of
// properties (`Prop`), or just property names (`Propname`).
type Propfind struct {
	XMLName  xml.Name `xml:"DAV: propfind"`
	Allprop  *struct{} `xml:"DAV: allprop"`
	Prop     *Prop     `xml:"DAV: prop"`
	Propname *struct{} `xml:"DAV: propname"`
}

// Prop represents a container for specific properties requested or returned
// in PROPFIND and PROPPATCH methods. Each field corresponds to a DAV property.
type Prop struct {
	XMLName          xml.Name      `xml:"DAV: prop"`
	GetContentLength *string       `xml:"DAV: getcontentlength,omitempty"`
	GetLastModified  *string       `xml:"DAV: getlastmodified,omitempty"`
	GetContentType   *string       `xml:"DAV: getcontenttype,omitempty"`
	ResourceType     *ResourceType `xml:"DAV: resourcetype,omitempty"`
	CreationDate     *string       `xml:"DAV: creationdate,omitempty"`
	DisplayName      *string       `xml:"DAV: displayname,omitempty"`
	SupportedLock    *SupportedLock `xml:"DAV: supportedlock,omitempty"`
	LockDiscovery    *LockDiscovery `xml:"DAV: lockdiscovery,omitempty"`
}

// LockDiscovery contains information about the active locks on a resource.
type LockDiscovery struct {
	XMLName    xml.Name     `xml:"DAV: lockdiscovery"`
	ActiveLock []ActiveLock `xml:"DAV: activelock"`
}

// ActiveLock describes an active lock on a resource.
type ActiveLock struct {
	XMLName   xml.Name  `xml:"DAV: activelock"`
	LockType  LockType  `xml:"DAV: locktype"`
	LockScope LockScope `xml:"DAV: lockscope"`
	Depth     string    `xml:"DAV: depth"`
	Owner     Owner     `xml:"DAV: owner"`
	Timeout   string    `xml:"DAV: timeout"`
	LockToken *LockToken `xml:"DAV: locktoken,omitempty"`
}

// LockToken represents a lock token.
type LockToken struct {
	XMLName xml.Name `xml:"DAV: locktoken"`
	Href    string   `xml:"DAV: href"`
}

// ResourceType indicates the nature of a resource, typically whether it is
// a collection (directory) or a standard resource.
type ResourceType struct {
	XMLName    xml.Name    `xml:"DAV: resourcetype"`
	Collection *struct{}   `xml:"DAV: collection,omitempty"`
}

// SupportedLock defines the types of locks supported by a resource.
type SupportedLock struct {
	XMLName   xml.Name    `xml:"DAV: supportedlock"`
	LockEntry []LockEntry `xml:"DAV: lockentry"`
}

// LockEntry describes a single type of lock that is supported.
type LockEntry struct {
	XMLName   xml.Name  `xml:"DAV: lockentry"`
	LockScope LockScope `xml:"DAV: lockscope"`
	LockType  LockType  `xml:"DAV: locktype"`
}

// LockScope specifies whether a lock is exclusive or shared.
type LockScope struct {
	XMLName   xml.Name    `xml:"DAV: lockscope"`
	Exclusive *struct{}   `xml:"DAV: exclusive,omitempty"`
	Shared    *struct{}   `xml:"DAV: shared,omitempty"`
}

// LockType indicates the type of lock, typically a write lock.
type LockType struct {
	XMLName xml.Name  `xml:"DAV: locktype"`
	Write   *struct{} `xml:"DAV: write,omitempty"`
}

// Multistatus is the root element for responses to PROPFIND and PROPPATCH
// requests, containing multiple individual responses for different resources.
type Multistatus struct {
	XMLName   xml.Name    `xml:"DAV: multistatus"`
	Responses []*Response `xml:"DAV: response"`
}

// Response represents the status and properties of a single resource within
// a Multistatus response.
type Response struct {
	XMLName   xml.Name   `xml:"DAV: response"`
	Href      []string   `xml:"DAV: href"`
	Propstats []Propstat `xml:"DAV: propstat"`
}

var multistatusPool = sync.Pool{
	New: func() interface{} {
		return &Multistatus{
			Responses: make([]*Response, 0),
		}
	},
}

// Propstat groups properties with their corresponding HTTP status in a
// single response, indicating success or failure for those properties.
type Propstat struct {
	XMLName xml.Name `xml:"DAV: propstat"`
	Prop    Prop     `xml:"DAV: prop"`
	Status  string   `xml:"DAV: status"`
}

// LockSystem is the interface for a lock manager.
type LockSystem interface {
	// Create creates a new lock.
	Create(ctx context.Context, path string, lockInfo LockInfo) (string, error)
	// Refresh refreshes an existing lock.
	Refresh(ctx context.Context, token string, timeout time.Duration) error
	// Unlock removes a lock.
	Unlock(ctx context.Context, token string) error
}

// Handler handles WebDAV requests.
type Handler struct {
	// Prefix is the URL prefix that the handler is mounted on.
	Prefix string
	// FileSystem is the file system that is served.
	FileSystem FileSystem
	// LockSystem is the lock system. If nil, locking is disabled.
	LockSystem LockSystem
	// Logger is the logger to use. If nil, logging is disabled.
	Logger Logger
}

// LockInfo contains information about a lock.
type LockInfo struct {
	XMLName   xml.Name  `xml:"DAV: lockinfo"`
	LockScope LockScope `xml:"DAV: lockscope"`
	LockType  LockType  `xml:"DAV: locktype"`
	Owner     Owner     `xml:"DAV: owner"`
	Timeout   time.Duration
}

// Owner represents the owner of a lock.
type Owner struct {
	XMLName xml.Name `xml:"DAV: owner"`
	Href    string   `xml:"DAV: href"`
}

// Logger is a simple logging interface.
type Logger interface {
	Printf(format string, v ...interface{})
}

// NewHandler returns a new Handler.
func NewHandler(prefix string, fs FileSystem, ls LockSystem, logger Logger) *Handler {
	return &Handler{
		Prefix:     prefix,
		FileSystem: fs,
		LockSystem: ls,
		Logger:     logger,
	}
}

// ServeTouka handles a Touka request.
func (h *Handler) ServeTouka(c *touka.Context) {
	path := h.stripPrefix(c.Request.URL.Path)
	c.Set("webdav_path", path)

	switch c.Request.Method {
	case "OPTIONS":
		h.handleOptions(c)
	case "GET", "HEAD":
		h.handleGetHead(c)
	case "DELETE":
		h.handleDelete(c)
	case "PUT":
		h.handlePut(c)
	case "MKCOL":
		h.handleMkcol(c)
	case "COPY":
		h.handleCopy(c)
	case "MOVE":
		h.handleMove(c)
	case "PROPFIND":
		h.handlePropfind(c)
	case "PROPPATCH":
		h.handleProppatch(c)
	case "LOCK":
		h.handleLock(c)
	case "UNLOCK":
		h.handleUnlock(c)
	default:
		c.Status(http.StatusMethodNotAllowed)
	}
}

func (h *Handler) handleOptions(c *touka.Context) {
	allow := "OPTIONS, GET, HEAD, DELETE, PUT, MKCOL, COPY, MOVE, PROPFIND, PROPPATCH"
	dav := "1"
	if h.LockSystem != nil {
		allow += ", LOCK, UNLOCK"
		dav += ", 2"
	}

	c.SetHeader("Allow", allow)
	c.SetHeader("DAV", dav)
	c.Status(http.StatusOK)
}

func (h *Handler) handleGetHead(c *touka.Context) {
	path, _ := c.Get("webdav_path")
	file, err := h.FileSystem.OpenFile(c, path.(string), os.O_RDONLY, 0)
	if err != nil {
		if os.IsNotExist(err) {
			c.Status(http.StatusNotFound)
		} else {
			c.Status(http.StatusInternalServerError)
		}
		return
	}
	defer file.Close()

	info, err := file.Stat()
	if err != nil {
		c.Status(http.StatusInternalServerError)
		return
	}

	if info.IsDir() {
		c.Status(http.StatusForbidden)
		return
	}

	http.ServeContent(c.Writer, c.Request, info.Name(), info.ModTime(), file)
}

func (h *Handler) handleDelete(c *touka.Context) {
	path, _ := c.Get("webdav_path")
	pathStr := path.(string)

	info, err := h.FileSystem.Stat(c.Context(), pathStr)
	if err != nil {
		if os.IsNotExist(err) {
			c.Status(http.StatusNotFound)
		} else {
			c.Status(http.StatusInternalServerError)
		}
		return
	}

	if info.IsDir() {
		file, err := h.FileSystem.OpenFile(c, pathStr, os.O_RDONLY, 0)
		if err != nil {
			c.Status(http.StatusInternalServerError)
			return
		}
		defer file.Close()

		// Check if the directory has any children. Readdir(1) is enough.
		children, err := file.Readdir(1)
		if err != nil && err != io.EOF {
			c.Status(http.StatusInternalServerError)
			return
		}
		if len(children) > 0 {
			c.Status(http.StatusConflict) // 409 Conflict for non-empty collection
			return
		}
	}

	if err := h.FileSystem.RemoveAll(c.Context(), pathStr); err != nil {
		if os.IsNotExist(err) {
			c.Status(http.StatusNotFound)
		} else {
			c.Status(http.StatusInternalServerError)
		}
		return
	}
	c.Status(http.StatusNoContent)
}

func (h *Handler) handlePut(c *touka.Context) {
	path, _ := c.Get("webdav_path")
	file, err := h.FileSystem.OpenFile(c, path.(string), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
	if err != nil {
		c.Status(http.StatusInternalServerError)
		return
	}
	defer file.Close()

	if _, err := io.Copy(file, c.Request.Body); err != nil {
		c.Status(http.StatusInternalServerError)
		return
	}

	c.Status(http.StatusCreated)
}

func (h *Handler) handleMkcol(c *touka.Context) {
	path, _ := c.Get("webdav_path")
	if err := h.FileSystem.Mkdir(c.Context(), path.(string), 0755); err != nil {
		if os.IsExist(err) {
			c.Status(http.StatusMethodNotAllowed)
		} else {
			c.Status(http.StatusInternalServerError)
		}
		return
	}
	c.Status(http.StatusCreated)
}

func (h *Handler) handleCopy(c *touka.Context) {
    srcPath, _ := c.Get("webdav_path")
    destPath := c.GetReqHeader("Destination")
    if destPath == "" {
        c.Status(http.StatusBadRequest)
        return
    }

    // A more complete implementation would parse the full URL.
    // For now, we assume the destination is a simple path.
    destURL, err := url.Parse(destPath)
    if err != nil {
        c.Status(http.StatusBadRequest)
        return
    }
    destPath = h.stripPrefix(destURL.Path)

    overwrite := c.GetReqHeader("Overwrite")
    if overwrite == "" {
        overwrite = "T" // Default is to overwrite
    }

    // Check for existence before the operation to determine status code later.
	_, err = h.FileSystem.Stat(c.Context(), destPath)
	existed := err == nil

    if overwrite == "F" && existed {
        c.Status(http.StatusPreconditionFailed)
        return
    }

    if err := h.copy(c, srcPath.(string), destPath); err != nil {
        c.Status(http.StatusInternalServerError)
        return
    }

	if existed {
		c.Status(http.StatusNoContent)
	} else {
		c.Status(http.StatusCreated)
	}
}

func (h *Handler) handleMove(c *touka.Context) {
    srcPath, _ := c.Get("webdav_path")
    destPath := c.GetReqHeader("Destination")
    if destPath == "" {
        c.Status(http.StatusBadRequest)
        return
    }

    destURL, err := url.Parse(destPath)
    if err != nil {
        c.Status(http.StatusBadRequest)
        return
    }
    destPath = h.stripPrefix(destURL.Path)

    overwrite := c.GetReqHeader("Overwrite")
    if overwrite == "" {
        overwrite = "T" // Default is to overwrite
    }

    // Check for existence before the operation to determine status code later.
	_, err = h.FileSystem.Stat(c.Context(), destPath)
	existed := err == nil

    if overwrite == "F" && existed {
        c.Status(http.StatusPreconditionFailed)
        return
    }

    if err := h.FileSystem.Rename(c.Context(), srcPath.(string), destPath); err != nil {
        c.Status(http.StatusInternalServerError)
        return
    }

	if existed {
		c.Status(http.StatusNoContent)
	} else {
		c.Status(http.StatusCreated)
	}
}

func (h *Handler) copy(c *touka.Context, src, dest string) error {
	info, err := h.FileSystem.Stat(c.Context(), src)
	if err != nil {
		return err
	}

	if info.IsDir() {
		if err := h.FileSystem.Mkdir(c.Context(), dest, info.Mode()); err != nil {
			return err
		}

		srcFile, err := h.FileSystem.OpenFile(c, src, os.O_RDONLY, 0)
		if err != nil {
			return err
		}
		defer srcFile.Close()

		children, err := srcFile.Readdir(0)
		if err != nil {
			return err
		}

		for _, child := range children {
			if err := h.copy(c, path.Join(src, child.Name()), path.Join(dest, child.Name())); err != nil {
				return err
			}
		}
		return nil
	}

	srcFile, err := h.FileSystem.OpenFile(c, src, os.O_RDONLY, 0)
	if err != nil {
		return err
	}
	defer srcFile.Close()

	destFile, err := h.FileSystem.OpenFile(c, dest, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, info.Mode())
	if err != nil {
		return err
	}
	defer destFile.Close()

	_, err = io.Copy(destFile, srcFile)
	return err
}

func (h *Handler) handlePropfind(c *touka.Context) {
	requestPath, _ := c.Get("webdav_path")
	info, err := h.FileSystem.Stat(c.Context(), requestPath.(string))
	if err != nil {
		if os.IsNotExist(err) {
			c.Status(http.StatusNotFound)
		} else {
			c.Status(http.StatusInternalServerError)
		}
		return
	}

	var propfind Propfind
	if c.Request.ContentLength != 0 {
		if err := xml.NewDecoder(c.Request.Body).Decode(&propfind); err != nil {
			c.Status(http.StatusBadRequest)
			return
		}
	}

	ms := multistatusPool.Get().(*Multistatus)
	defer func() {
		ms.Responses = ms.Responses[:0]
		multistatusPool.Put(ms)
	}()

	depth := c.GetReqHeader("Depth")
	if depth == "" {
		depth = "infinity"
	}

	ms.Responses = append(ms.Responses, h.createPropfindResponse(requestPath.(string), info, propfind))

	if info.IsDir() && depth != "0" {
		var walk func(string, int) error
		walk = func(p string, maxDepth int) error {
			if maxDepth == 0 {
				return nil
			}

			file, err := h.FileSystem.OpenFile(c, p, os.O_RDONLY, 0)
			if err != nil {
				return err
			}
			defer file.Close()

			children, err := file.Readdir(0)
			if err != nil {
				return err
			}

			for _, child := range children {
				childPath := path.Join(p, child.Name())
				childInfo, err := h.FileSystem.Stat(c.Context(), childPath)
				if err != nil {
					if h.Logger != nil {
						h.Logger.Printf("PROPFIND walk: failed to stat child %s: %v", childPath, err)
					}
					continue
				}
				ms.Responses = append(ms.Responses, h.createPropfindResponse(childPath, childInfo, propfind))
				if childInfo.IsDir() {
					if err := walk(childPath, maxDepth-1); err != nil {
						return err
					}
				}
			}
			return nil
		}

		walkDepth := -1
		if depth == "1" {
			walkDepth = 1
		}

		if err := walk(requestPath.(string), walkDepth); err != nil {
			if h.Logger != nil {
				h.Logger.Printf("Error during PROPFIND walk: %v", err)
			}
			c.Status(http.StatusInternalServerError)
			return
		}
	}

	c.Writer.Header().Set("Content-Type", "application/xml; charset=utf-8")
	c.Status(http.StatusMultiStatus)
	if err := xml.NewEncoder(c.Writer).Encode(ms); err != nil {
		h.Logger.Printf("Error encoding propfind response: %v", err)
	}
}


func (h *Handler) createPropfindResponse(p string, info ObjectInfo, propfind Propfind) *Response {
	fullPath := path.Join(h.Prefix, p)

	resp := &Response{
		Href:      []string{fullPath},
		Propstats: make([]Propstat, 0),
	}

	prop := Prop{}
	if propfind.Allprop != nil {
		prop.GetContentLength = new(string)
		*prop.GetContentLength = fmt.Sprintf("%d", info.Size())

		prop.GetLastModified = new(string)
		*prop.GetLastModified = info.ModTime().Format(http.TimeFormat)

		prop.ResourceType = &ResourceType{}
		if info.IsDir() {
			prop.ResourceType.Collection = &struct{}{}
		}
	} else if propfind.Prop != nil {
		if propfind.Prop.GetContentLength != nil {
			prop.GetContentLength = new(string)
			*prop.GetContentLength = fmt.Sprintf("%d", info.Size())
		}
		if propfind.Prop.GetLastModified != nil {
			prop.GetLastModified = new(string)
			*prop.GetLastModified = info.ModTime().Format(http.TimeFormat)
		}
		if propfind.Prop.ResourceType != nil {
			prop.ResourceType = &ResourceType{}
			if info.IsDir() {
				prop.ResourceType.Collection = &struct{}{}
			}
		}
	}

	resp.Propstats = append(resp.Propstats, Propstat{
		Prop:   prop,
		Status: "HTTP/1.1 200 OK",
	})

	return resp
}

func (h *Handler) handleProppatch(c *touka.Context) {
	c.Status(http.StatusNotImplemented)
}

func (h *Handler) stripPrefix(p string) string {
	return strings.TrimPrefix(strings.TrimPrefix(p, h.Prefix), "/")
}

func (h *Handler) handleLock(c *touka.Context) {
	if h.LockSystem == nil {
		c.Status(http.StatusMethodNotAllowed)
		return
	}

	path, _ := c.Get("webdav_path")
	tokenHeader := c.GetReqHeader("If")
	var token string
	if tokenHeader != "" {
		// Basic parsing for <opaquelocktoken:c2134f...>
		if strings.HasPrefix(tokenHeader, "(<") && strings.HasSuffix(tokenHeader, ">)") {
			token = strings.TrimPrefix(tokenHeader, "(<")
			token = strings.TrimSuffix(token, ">)")
		}
	}

	// Refresh lock
	if token != "" {
		timeoutStr := c.GetReqHeader("Timeout")
		timeout, err := parseTimeout(timeoutStr)
		if err != nil {
			c.Status(http.StatusBadRequest)
			return
		}

		if err := h.LockSystem.Refresh(c.Context(), token, timeout); err != nil {
			c.Status(http.StatusPreconditionFailed)
			return
		}
	} else {
		// Create lock
		var lockInfo LockInfo
		if err := xml.NewDecoder(c.Request.Body).Decode(&lockInfo); err != nil {
			c.Status(http.StatusBadRequest)
			return
		}

		timeoutStr := c.GetReqHeader("Timeout")
		timeout, err := parseTimeout(timeoutStr)
		if err != nil {
			c.Status(http.StatusBadRequest)
			return
		}
		lockInfo.Timeout = timeout

		token, err = h.LockSystem.Create(c.Context(), path.(string), lockInfo)
		if err != nil {
			c.Status(http.StatusConflict)
			return
		}
	}

	prop := Prop{
		LockDiscovery: &LockDiscovery{
			ActiveLock: []ActiveLock{
				{
					LockToken: &LockToken{Href: token},
				},
			},
		},
	}

	c.Writer.Header().Set("Content-Type", "application/xml; charset=utf-8")
	c.Writer.Header().Set("Lock-Token", token)
	c.Status(http.StatusOK)
	xml.NewEncoder(c.Writer).Encode(prop)
}

func parseTimeout(timeoutStr string) (time.Duration, error) {
	if timeoutStr == "" || strings.ToLower(timeoutStr) == "infinite" {
		// A long timeout, as per RFC 4918.
		return 10 * time.Minute, nil
	}
	// "Second-123"
	parts := strings.Split(timeoutStr, "-")
	if len(parts) == 2 && strings.ToLower(parts[0]) == "second" {
		seconds, err := time.ParseDuration(parts[1] + "s")
		if err == nil {
			return seconds, nil
		}
	}
	return 0, os.ErrInvalid
}

func (h *Handler) handleUnlock(c *touka.Context) {
	if h.LockSystem == nil {
		c.Status(http.StatusMethodNotAllowed)
		return
	}

	tokenHeader := c.GetReqHeader("Lock-Token")
	if tokenHeader == "" {
		c.Status(http.StatusBadRequest)
		return
	}

	// Basic parsing for <urn:uuid:f81d4fae...>
	token := strings.TrimPrefix(tokenHeader, "<")
	token = strings.TrimSuffix(token, ">")

	if err := h.LockSystem.Unlock(c.Context(), token); err != nil {
		c.Status(http.StatusConflict)
		return
	}

	c.Status(http.StatusNoContent)
}