package api

import (
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/gorilla/mux"
	"github.com/mattermost/focalboard/server/app"
	"github.com/mattermost/focalboard/server/model"
	"github.com/mattermost/focalboard/server/utils"
)

const (
	HEADER_REQUESTED_WITH     = "X-Requested-With"
	HEADER_REQUESTED_WITH_XML = "XMLHttpRequest"
)

// ----------------------------------------------------------------------------------------------------
// REST APIs

type API struct {
	appBuilder      func() *app.App
	singleUserToken string
}

func NewAPI(appBuilder func() *app.App, singleUserToken string) *API {
	return &API{
		appBuilder:      appBuilder,
		singleUserToken: singleUserToken,
	}
}

func (a *API) app() *app.App {
	return a.appBuilder()
}

func (a *API) RegisterRoutes(r *mux.Router) {
	apiv1 := r.PathPrefix("/api/v1").Subrouter()
	apiv1.Use(a.requireCSRFToken)

	apiv1.HandleFunc("/blocks", a.sessionRequired(a.handleGetBlocks)).Methods("GET")
	apiv1.HandleFunc("/blocks", a.sessionRequired(a.handlePostBlocks)).Methods("POST")
	apiv1.HandleFunc("/blocks/{blockID}", a.sessionRequired(a.handleDeleteBlock)).Methods("DELETE")
	apiv1.HandleFunc("/blocks/{blockID}/subtree", a.attachSession(a.handleGetSubTree, false)).Methods("GET")

	apiv1.HandleFunc("/users/me", a.sessionRequired(a.handleGetMe)).Methods("GET")
	apiv1.HandleFunc("/users/{userID}", a.sessionRequired(a.handleGetUser)).Methods("GET")
	apiv1.HandleFunc("/users/{userID}/changepassword", a.sessionRequired(a.handleChangePassword)).Methods("POST")

	apiv1.HandleFunc("/login", a.handleLogin).Methods("POST")
	apiv1.HandleFunc("/register", a.handleRegister).Methods("POST")

	apiv1.HandleFunc("/files", a.sessionRequired(a.handleUploadFile)).Methods("POST")

	apiv1.HandleFunc("/blocks/export", a.sessionRequired(a.handleExport)).Methods("GET")
	apiv1.HandleFunc("/blocks/import", a.sessionRequired(a.handleImport)).Methods("POST")

	apiv1.HandleFunc("/sharing/{rootID}", a.sessionRequired(a.handlePostSharing)).Methods("POST")
	apiv1.HandleFunc("/sharing/{rootID}", a.sessionRequired(a.handleGetSharing)).Methods("GET")

	apiv1.HandleFunc("/workspace", a.sessionRequired(a.handleGetWorkspace)).Methods("GET")
	apiv1.HandleFunc("/workspace/regenerate_signup_token", a.sessionRequired(a.handlePostWorkspaceRegenerateSignupToken)).Methods("POST")

	// Get Files API

	files := r.PathPrefix("/files").Subrouter()
	files.HandleFunc("/{filename}", a.sessionRequired(a.handleServeFile)).Methods("GET")
}

func (a *API) RegisterAdminRoutes(r *mux.Router) {
	r.HandleFunc("/api/v1/admin/users/{username}/password", a.adminRequired(a.handleAdminSetPassword)).Methods("POST")
}

func (a *API) requireCSRFToken(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !a.checkCSRFToken(r) {
			log.Println("checkCSRFToken FAILED")
			errorResponse(w, http.StatusBadRequest, "", nil)
			return
		}

		next.ServeHTTP(w, r)
	})
}

func (a *API) checkCSRFToken(r *http.Request) bool {
	token := r.Header.Get(HEADER_REQUESTED_WITH)

	if token == HEADER_REQUESTED_WITH_XML {
		return true
	}

	return false
}

func (a *API) handleGetBlocks(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/blocks getBlocks
	//
	// Returns blocks
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: parent_id
	//   in: query
	//   description: ID of parent block, omit to specify all blocks
	//   required: false
	//   type: string
	// - name: type
	//   in: query
	//   description: Type of blocks to return, omit to specify all types
	//   required: false
	//   type: string
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       type: array
	//       items:
	//         "$ref": "#/definitions/Block"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	query := r.URL.Query()
	parentID := query.Get("parent_id")
	blockType := query.Get("type")

	blocks, err := a.app().GetBlocks(parentID, blockType)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	// log.Printf("GetBlocks parentID: %s, type: %s, %d result(s)", parentID, blockType, len(blocks))

	json, err := json.Marshal(blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, json)
}

func stampModifiedByUser(r *http.Request, blocks []model.Block) {
	ctx := r.Context()
	session := ctx.Value("session").(*model.Session)
	userID := session.UserID
	if userID == "single-user" {
		userID = ""
	}

	for i := range blocks {
		blocks[i].ModifiedBy = userID
	}
}

func (a *API) handlePostBlocks(w http.ResponseWriter, r *http.Request) {
	// swagger:operation POST /api/v1/blocks updateBlocks
	//
	// Insert or update blocks
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: Body
	//   in: body
	//   description: array of blocks to insert or update
	//   required: true
	//   schema:
	//     type: array
	//     items:
	//       "$ref": "#/definitions/Block"
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	requestBody, err := ioutil.ReadAll(r.Body)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	var blocks []model.Block

	err = json.Unmarshal(requestBody, &blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	for _, block := range blocks {
		// Error checking
		if len(block.Type) < 1 {
			message := fmt.Sprintf("missing type for block id %s", block.ID)
			errorResponse(w, http.StatusBadRequest, message, nil)
			return
		}

		if block.CreateAt < 1 {
			message := fmt.Sprintf("invalid createAt for block id %s", block.ID)
			errorResponse(w, http.StatusBadRequest, message, nil)
			return
		}

		if block.UpdateAt < 1 {
			message := fmt.Sprintf("invalid UpdateAt for block id %s", block.ID)
			errorResponse(w, http.StatusBadRequest, message, nil)
			return
		}
	}

	stampModifiedByUser(r, blocks)

	err = a.app().InsertBlocks(blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("POST Blocks %d block(s)", len(blocks))
	jsonStringResponse(w, http.StatusOK, "{}")
}

func (a *API) handleGetUser(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/users/{userID} getUser
	//
	// Returns a user
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: userID
	//   in: path
	//   description: User ID
	//   required: true
	//   type: string
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       "$ref": "#/definitions/User"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	vars := mux.Vars(r)
	userID := vars["userID"]

	user, err := a.app().GetUser(userID)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	userData, err := json.Marshal(user)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, userData)
}

func (a *API) handleGetMe(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/users/me getMe
	//
	// Returns the currently logged-in user
	//
	// ---
	// produces:
	// - application/json
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       "$ref": "#/definitions/User"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	ctx := r.Context()
	session := ctx.Value("session").(*model.Session)
	var user *model.User
	var err error

	if session.UserID == "single-user" {
		now := time.Now().Unix()
		user = &model.User{
			ID:       "single-user",
			Username: "single-user",
			Email:    "single-user",
			CreateAt: now,
			UpdateAt: now,
		}
	} else {
		user, err = a.app().GetUser(session.UserID)
		if err != nil {
			errorResponse(w, http.StatusInternalServerError, "", err)
			return
		}
	}

	userData, err := json.Marshal(user)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, userData)
}

func (a *API) handleDeleteBlock(w http.ResponseWriter, r *http.Request) {
	// swagger:operation DELETE /api/v1/blocks/{blockID} deleteBlock
	//
	// Deletes a block
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: blockID
	//   in: path
	//   description: ID of block to delete
	//   required: true
	//   type: string
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	ctx := r.Context()
	session := ctx.Value("session").(*model.Session)
	userID := session.UserID

	vars := mux.Vars(r)
	blockID := vars["blockID"]

	err := a.app().DeleteBlock(blockID, userID)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)

		return
	}

	log.Printf("DELETE Block %s", blockID)
	jsonStringResponse(w, http.StatusOK, "{}")
}

func (a *API) handleGetSubTree(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/blocks/{blockID}/subtree getSubTree
	//
	// Returns the blocks of a subtree
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: blockID
	//   in: path
	//   description: The ID of the root block of the subtree
	//   required: true
	//   type: string
	// - name: l
	//   in: query
	//   description: The number of levels to return. 2 or 3. Defaults to 2.
	//   required: false
	//   type: integer
	//   minimum: 2
	//   maximum: 3
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       type: array
	//       items:
	//         "$ref": "#/definitions/Block"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	vars := mux.Vars(r)
	blockID := vars["blockID"]

	// If not authenticated (no session), check that block is publicly shared
	ctx := r.Context()
	session, _ := ctx.Value("session").(*model.Session)
	if session == nil {
		query := r.URL.Query()
		readToken := query.Get("read_token")

		// Require read token
		if len(readToken) < 1 {
			errorResponse(w, http.StatusBadRequest, "No read_token", nil)
			return
		}

		isValid, err := a.app().IsValidReadToken(blockID, readToken)
		if err != nil {
			errorResponse(w, http.StatusInternalServerError, "", err)
			return
		}

		if !isValid {
			errorResponse(w, http.StatusUnauthorized, "", nil)
			return
		}
	}

	query := r.URL.Query()
	levels, err := strconv.ParseInt(query.Get("l"), 10, 32)
	if err != nil {
		levels = 2
	}

	if levels != 2 && levels != 3 {
		log.Printf(`ERROR Invalid levels: %d`, levels)
		errorResponse(w, http.StatusBadRequest, "invalid levels", nil)
		return
	}

	blocks, err := a.app().GetSubTree(blockID, int(levels))
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("GetSubTree (%v) blockID: %s, %d result(s)", levels, blockID, len(blocks))
	json, err := json.Marshal(blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, json)
}

func (a *API) handleExport(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/blocks/export exportBlocks
	//
	// Returns all blocks
	//
	// ---
	// produces:
	// - application/json
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       type: array
	//       items:
	//         "$ref": "#/definitions/Block"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	blocks, err := a.app().GetAllBlocks()
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("%d raw block(s)", len(blocks))
	blocks = filterOrphanBlocks(blocks)
	log.Printf("EXPORT %d filtered block(s)", len(blocks))

	json, err := json.Marshal(blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, json)
}

func filterOrphanBlocks(blocks []model.Block) (ret []model.Block) {
	queue := make([]model.Block, 0)
	childrenOfBlockWithID := make(map[string]*[]model.Block)

	// Build the trees from nodes
	for _, block := range blocks {
		if len(block.ParentID) == 0 {
			// Queue root blocks to process first
			queue = append(queue, block)
		} else {
			siblings := childrenOfBlockWithID[block.ParentID]
			if siblings != nil {
				*siblings = append(*siblings, block)
			} else {
				siblings := []model.Block{block}
				childrenOfBlockWithID[block.ParentID] = &siblings
			}
		}
	}

	// Map the trees to an array, which skips orphaned nodes
	blocks = make([]model.Block, 0)
	for len(queue) > 0 {
		block := queue[0]
		queue = queue[1:] // dequeue
		blocks = append(blocks, block)
		children := childrenOfBlockWithID[block.ID]
		if children != nil {
			queue = append(queue, (*children)...)
		}
	}

	return blocks
}

func arrayContainsBlockWithID(array []model.Block, blockID string) bool {
	for _, item := range array {
		if item.ID == blockID {
			return true
		}
	}
	return false
}

func (a *API) handleImport(w http.ResponseWriter, r *http.Request) {
	// swagger:operation POST /api/v1/blocks/import importBlocks
	//
	// Import blocks
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: Body
	//   in: body
	//   description: array of blocks to import
	//   required: true
	//   schema:
	//     type: array
	//     items:
	//       "$ref": "#/definitions/Block"
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	requestBody, err := ioutil.ReadAll(r.Body)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	var blocks []model.Block

	err = json.Unmarshal(requestBody, &blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	stampModifiedByUser(r, blocks)

	err = a.app().InsertBlocks(blocks)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("IMPORT Blocks %d block(s)", len(blocks))
	jsonStringResponse(w, http.StatusOK, "{}")
}

// Sharing

func (a *API) handleGetSharing(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/sharing/{rootID} getSharing
	//
	// Returns sharing information for a root block
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: rootID
	//   in: path
	//   description: ID of the root block
	//   required: true
	//   type: string
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       "$ref": "#/definitions/Sharing"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	vars := mux.Vars(r)
	rootID := vars["rootID"]

	sharing, err := a.app().GetSharing(rootID)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	sharingData, err := json.Marshal(sharing)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("GET sharing %s", rootID)
	jsonBytesResponse(w, http.StatusOK, sharingData)
}

func (a *API) handlePostSharing(w http.ResponseWriter, r *http.Request) {
	// swagger:operation POST /api/v1/sharing/{rootID} postSharing
	//
	// Sets sharing information for a root block
	//
	// ---
	// produces:
	// - application/json
	// parameters:
	// - name: rootID
	//   in: path
	//   description: ID of the root block
	//   required: true
	//   type: string
	// - name: Body
	//   in: body
	//   description: sharing information for a root block
	//   required: true
	//   schema:
	//     "$ref": "#/definitions/Sharing"
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	requestBody, err := ioutil.ReadAll(r.Body)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	var sharing model.Sharing

	err = json.Unmarshal(requestBody, &sharing)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	// Stamp ModifiedBy
	ctx := r.Context()
	session := ctx.Value("session").(*model.Session)
	userID := session.UserID
	if userID == "single-user" {
		userID = ""
	}
	sharing.ModifiedBy = userID

	err = a.app().UpsertSharing(sharing)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("POST sharing %s", sharing.ID)
	jsonStringResponse(w, http.StatusOK, "{}")
}

// Workspace

func (a *API) handleGetWorkspace(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /api/v1/workspace getWorkspace
	//
	// Returns information of the root workspace
	//
	// ---
	// produces:
	// - application/json
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       "$ref": "#/definitions/Workspace"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	workspace, err := a.app().GetRootWorkspace()
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	workspaceData, err := json.Marshal(workspace)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, workspaceData)
}

func (a *API) handlePostWorkspaceRegenerateSignupToken(w http.ResponseWriter, r *http.Request) {
	// swagger:operation POST /api/v1/workspace/regenerate_signup_token regenerateSignupToken
	//
	// Regenerates the signup token for the root workspace
	//
	// ---
	// produces:
	// - application/json
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	workspace, err := a.app().GetRootWorkspace()
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	workspace.SignupToken = utils.CreateGUID()

	err = a.app().UpsertWorkspaceSignupToken(*workspace)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonStringResponse(w, http.StatusOK, "{}")
}

// File upload

func (a *API) handleServeFile(w http.ResponseWriter, r *http.Request) {
	// swagger:operation GET /files/{fileID} getFile
	//
	// Returns the contents of an uploaded file
	//
	// ---
	// produces:
	// - application/json
	// - image/jpg
	// - image/png
	// parameters:
	// - name: fileID
	//   in: path
	//   description: ID of the file
	//   required: true
	//   type: string
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	vars := mux.Vars(r)
	filename := vars["filename"]

	contentType := "image/jpg"

	fileExtension := strings.ToLower(filepath.Ext(filename))
	if fileExtension == "png" {
		contentType = "image/png"
	}

	w.Header().Set("Content-Type", contentType)

	filePath := a.app().GetFilePath(filename)
	http.ServeFile(w, r, filePath)
}

// FileUploadResponse is the response to a file upload
// swagger:model
type FileUploadResponse struct {
	// The FileID to retrieve the uploaded file
	// required: true
	FileID string `json:"fileId"`
}

func (a *API) handleUploadFile(w http.ResponseWriter, r *http.Request) {
	// swagger:operation POST /api/v1/files uploadFile
	//
	// Upload a binary file
	//
	// ---
	// consumes:
	// - multipart/form-data
	// produces:
	// - application/json
	// parameters:
	// - name: uploaded file
	//   in: formData
	//   type: file
	//   description: The file to upload
	// security:
	// - BearerAuth: []
	// responses:
	//   '200':
	//     description: success
	//     schema:
	//       "$ref": "#/definitions/FileUploadResponse"
	//   default:
	//     description: internal error
	//     schema:
	//       "$ref": "#/definitions/ErrorResponse"

	file, handle, err := r.FormFile("file")
	if err != nil {
		fmt.Fprintf(w, "%v", err)

		return
	}
	defer file.Close()

	fileId, err := a.app().SaveFile(file, handle.Filename)
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	log.Printf("uploadFile, filename: %s, fileId: %s", handle.Filename, fileId)
	data, err := json.Marshal(FileUploadResponse{FileID: fileId})
	if err != nil {
		errorResponse(w, http.StatusInternalServerError, "", err)
		return
	}

	jsonBytesResponse(w, http.StatusOK, data)
}

// Response helpers

func jsonStringResponse(w http.ResponseWriter, code int, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	fmt.Fprint(w, message)
}

func jsonBytesResponse(w http.ResponseWriter, code int, json []byte) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	w.Write(json)
}

func errorResponse(w http.ResponseWriter, code int, message string, sourceError error) {
	log.Printf("API ERROR %d, err: %v\n", code, sourceError)
	w.Header().Set("Content-Type", "application/json")
	data, err := json.Marshal(model.ErrorResponse{Error: message})
	if err != nil {
		data = []byte("{}")
	}
	w.WriteHeader(code)
	w.Write(data)
}

func addUserID(rw http.ResponseWriter, req *http.Request, next http.Handler) {
	ctx := context.WithValue(req.Context(), "userid", req.Header.Get("userid"))
	req = req.WithContext(ctx)
	next.ServeHTTP(rw, req)
}