package clientapi

import (
	"encoding/json"
	"errors"
	"net/http"
	"strings"

	"github.com/dariuszjaniak/warp/server/internal/httputil"
	"github.com/dariuszjaniak/warp/server/internal/pushserver"
	"github.com/dariuszjaniak/warp/server/internal/userapi"
)

// MaxAccountDataSize caps one account data blob. The spec sets no limit, but
// account data is sent down /sync in full on every initial sync, so an
// unbounded blob is an unbounded sync.
const MaxAccountDataSize = 64 * 1024

// typeFullyRead is the account data type the spec reserves: it is set
// through POST /rooms/{roomId}/read_markers, which keeps the read marker and
// the receipt in step, so writing it directly is refused.
const typeFullyRead = "m.fully_read"

// handleGetAccountData implements
// GET /_matrix/client/v3/user/{userId}/account_data/{type}.
func (c *ClientAPI) handleGetAccountData(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	return c.getAccountData(w, r, auth, "")
}

// handleGetRoomAccountData implements the per-room variant.
func (c *ClientAPI) handleGetRoomAccountData(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID := r.PathValue("roomID")
	if err := validateRoomID(roomID); err != nil {
		return err
	}
	return c.getAccountData(w, r, auth, roomID)
}

func (c *ClientAPI) getAccountData(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated, roomID string) error {
	// Account data is private, so even a read is only ever of one's own —
	// an admin reading it would be reading a user's client settings, which
	// the admin API has no business doing either.
	localpart, err := c.requireOwnAccountData(auth, r.PathValue("userID"))
	if err != nil {
		return err
	}
	dataType := r.PathValue("dataType")
	if dataType == "" {
		return httputil.MissingParam("An account data type is required")
	}

	var content []byte
	if roomID == "" && dataType == pushserver.AccountDataType && c.push != nil {
		// The push server's, rendered over the defaults: a user who never
		// changed a rule has nothing stored and still has rules.
		content, err = c.push.Document(r.Context(), localpart, auth.UserID)
	} else {
		content, err = c.users.AccountData(r.Context(), localpart, roomID, dataType)
	}
	switch {
	case errors.Is(err, userapi.ErrNoSuchAccountData):
		return httputil.NotFound("Account data not found")
	case err != nil:
		return err
	}

	// The stored bytes are the client's own JSON and go back out verbatim,
	// so they are written directly rather than round-tripped through a map.
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	if _, err := w.Write(content); err != nil {
		httputil.LoggerFrom(r.Context()).Debug("writing account data failed", "error", err)
	}
	return nil
}

// handlePutAccountData implements
// PUT /_matrix/client/v3/user/{userId}/account_data/{type}.
func (c *ClientAPI) handlePutAccountData(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	return c.putAccountData(w, r, auth, "")
}

// handlePutRoomAccountData implements the per-room variant.
func (c *ClientAPI) handlePutRoomAccountData(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID := r.PathValue("roomID")
	if err := validateRoomID(roomID); err != nil {
		return err
	}
	return c.putAccountData(w, r, auth, roomID)
}

func (c *ClientAPI) putAccountData(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated, roomID string) error {
	localpart, err := c.requireOwnAccountData(auth, r.PathValue("userID"))
	if err != nil {
		return err
	}
	dataType := r.PathValue("dataType")
	if dataType == "" {
		return httputil.MissingParam("An account data type is required")
	}
	if dataType == typeFullyRead {
		return httputil.BadJSON("%s may only be set through /rooms/{roomId}/read_markers", typeFullyRead)
	}
	if dataType == pushserver.AccountDataType {
		return httputil.NewError(http.StatusMethodNotAllowed, httputil.ErrCodeBadJSON,
			"%s may only be changed through the /pushrules endpoints", pushserver.AccountDataType)
	}

	// The content is stored as the client sent it, so it is read as raw
	// JSON and only checked for being a JSON object at all.
	var content json.RawMessage
	if err := httputil.DecodeJSON(w, r, &content); err != nil {
		return err
	}
	if len(content) > MaxAccountDataSize {
		return httputil.NewError(http.StatusBadRequest, httputil.ErrCodeTooLarge,
			"Account data must be at most %d bytes", MaxAccountDataSize)
	}
	if !json.Valid(content) {
		return httputil.NotJSON()
	}
	if trimmed := strings.TrimSpace(string(content)); !strings.HasPrefix(trimmed, "{") {
		return httputil.BadJSON("Account data content must be a JSON object")
	}

	if err := c.users.SetAccountData(r.Context(), localpart, roomID, dataType, content); err != nil {
		return err
	}
	// Account data reaches a client's other devices through /sync, and
	// one of them blocked in a long poll should hear about it now.
	if c.sync != nil {
		c.sync.Notifier().NotifyUser(auth.UserID)
	}
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// requireOwnAccountData resolves the path's user ID and insists it is the
// caller's own. Unlike a profile, account data is not something an admin may
// reach into: it is the user's client configuration.
func (c *ClientAPI) requireOwnAccountData(auth userapi.Authenticated, pathUserID string) (string, error) {
	localpart, err := c.users.ParseLocalUserID(pathUserID)
	switch {
	case errors.Is(err, userapi.ErrForeignServer):
		return "", httputil.Forbidden("Cannot access the account data of another server")
	case err != nil:
		return "", httputil.InvalidParam("%s is not a valid user ID", pathUserID)
	}
	if localpart != auth.Localpart {
		return "", httputil.Forbidden("Cannot access the account data of another user")
	}
	return localpart, nil
}

// validateRoomID checks the shape of a room ID in a path.
//
// Phase 1 has no rooms, so there is nothing to check it against: room
// account data is simply a second key space, and a client may set it for a
// room it has not joined. The full check — that the room exists and the user
// is in it — belongs to the roomserver in Phase 3.
func validateRoomID(roomID string) error {
	switch {
	case roomID == "":
		return httputil.MissingParam("A room ID is required")
	case !strings.HasPrefix(roomID, "!"):
		return httputil.InvalidParam("%s is not a valid room ID", roomID)
	case len(roomID) > 255:
		return httputil.InvalidParam("Room IDs must be at most 255 bytes")
	}
	return nil
}