src/pages/sign/index.tsx

@@ -34,6 +34,7 @@ import {
   CreateSignatureEventContent,
   Meta,
   ProfileMetadata,
+  SignedEventContent,
   User,
   UserRole
 } from '../../types'
@@ -52,7 +53,12 @@ import {
   uploadToFileStorage
 } from '../../utils'
 import styles from './style.module.scss'
-import { Download } from '@mui/icons-material'
+import {
+  Cancel,
+  CheckCircle,
+  Download,
+  HourglassTop
+} from '@mui/icons-material'
 
 enum SignedStatus {
   Fully_Signed,
@@ -350,9 +356,13 @@ export const SignPage = () => {
     setLoadingSpinnerDesc('Generating hashes for files')
 
     setLoadingSpinnerDesc('Signing nostr event')
+
+    const prevSig = getPrevSignersSig(hexToNpub(usersPubkey!))
+    if (!prevSig) return
+
     const signedEvent = await signEventForMetaFile(
       JSON.stringify({
-        fileHashes: currentFileHashes
+        prevSig
       }),
       nostrController,
       setIsLoading
@@ -461,7 +471,7 @@ export const SignPage = () => {
         key,
         npubToHex(nextSigner)!,
         nostrController,
-        false,
+        true,
         setAuthUrl
       )
     }
@@ -488,9 +498,13 @@ export const SignPage = () => {
 
     setIsLoading(true)
     setLoadingSpinnerDesc('Signing nostr event')
+
+    const prevSig = await getLastSignersSig()
+    if (!prevSig) return
+
     const signedEvent = await signEventForMetaFile(
       JSON.stringify({
-        fileHashes: currentFileHashes
+        prevSig
       }),
       nostrController,
       setIsLoading
@@ -535,6 +549,70 @@ export const SignPage = () => {
     navigate(appPrivateRoutes.verify)
   }
 
+  /**
+   * This function accepts an npub of a signer and return the signature of its previous signer.
+   * This prevSig will be used in the content of the provided signer's signedEvent
+   */
+  const getPrevSignersSig = (npub: string) => {
+    if (!meta) return null
+
+    // if user is first signer then use creator's signature
+    if (signers[0] === npub) {
+      try {
+        const createSignatureEvent: Event = JSON.parse(meta.createSignature)
+        return createSignatureEvent.sig
+      } catch (error) {
+        return null
+      }
+    }
+
+    // find the index of signer
+    const currentSignerIndex = signers.findIndex((signer) => signer === npub)
+    // return null if could not found user in signer's list
+    if (currentSignerIndex === -1) return null
+    // find prev signer
+    const prevSigner = signers[currentSignerIndex - 1]
+
+    // get the signature of prev signer
+    try {
+      const prevSignersEvent: Event = JSON.parse(meta.docSignatures[prevSigner])
+      return prevSignersEvent.sig
+    } catch (error) {
+      return null
+    }
+  }
+
+  /**
+   * This function returns the signature of last signer
+   * It will be used in the content of export signature's signedEvent
+   */
+  const getLastSignersSig = () => {
+    if (!meta) return null
+
+    // if there're no signers then use creator's signature
+    if (signers.length === 0) {
+      try {
+        const createSignatureEvent: Event = JSON.parse(meta.createSignature)
+        return createSignatureEvent.sig
+      } catch (error) {
+        return null
+      }
+    }
+
+    // get last signer
+    const lastSigner = signers[signers.length - 1]
+
+    // get the signature of last signer
+    try {
+      const lastSignatureEvent: Event = JSON.parse(
+        meta.docSignatures[lastSigner]
+      )
+      return lastSignatureEvent.sig
+    } catch (error) {
+      return null
+    }
+  }
+
   if (authUrl) {
     return (
       <iframe
@@ -583,9 +661,10 @@ export const SignPage = () => {
           </>
         )}
 
-        {submittedBy && zip && (
+        {submittedBy && zip && meta && (
           <>
             <DisplayMeta
+              meta={meta}
               zip={zip}
               submittedBy={submittedBy}
               signers={signers}
@@ -594,6 +673,7 @@ export const SignPage = () => {
               currentFileHashes={currentFileHashes}
               signedBy={signedBy}
               nextSigner={nextSinger}
+              getPrevSignersSig={getPrevSignersSig}
             />
             {signedStatus === SignedStatus.Fully_Signed && (
               <Box sx={{ mt: 1, display: 'flex', justifyContent: 'center' }}>
@@ -618,6 +698,7 @@ export const SignPage = () => {
 }
 
 type DisplayMetaProps = {
+  meta: Meta
   zip: JSZip
   submittedBy: string
   signers: `npub1${string}`[]
@@ -626,9 +707,11 @@ type DisplayMetaProps = {
   currentFileHashes: { [key: string]: string | null }
   signedBy: `npub1${string}`[]
   nextSigner?: string
+  getPrevSignersSig: (usersNpub: string) => string | null
 }
 
 const DisplayMeta = ({
+  meta,
   zip,
   submittedBy,
   signers,
@@ -636,7 +719,8 @@ const DisplayMeta = ({
   creatorFileHashes,
   currentFileHashes,
   signedBy,
-  nextSigner
+  nextSigner,
+  getPrevSignersSig
 }: DisplayMetaProps) => {
   const theme = useTheme()
 
@@ -784,16 +868,16 @@ const DisplayMeta = ({
                 >
                   {filename}
                 </Typography>
-                <Typography
+                {isValidHash && (
-                  component="label"
+                  <Tooltip title="File integrity check passed" arrow>
-                  sx={{
+                    <CheckCircle sx={{ color: theme.palette.success.light }} />
-                    color: isValidHash
+                  </Tooltip>
-                      ? theme.palette.success.light
+                )}
-                      : theme.palette.error.main
+                {!isValidHash && (
-                  }}
+                  <Tooltip title="File integrity check failed" arrow>
-                >
+                    <Cancel sx={{ color: theme.palette.error.main }} />
-                  {isValidHash ? 'Valid' : 'Invalid'} hash
+                  </Tooltip>
-                </Typography>
+                )}
               </Box>
             )
           })}
@@ -809,25 +893,138 @@ const DisplayMeta = ({
             </TableRow>
           </TableHead>
           <TableBody>
-            {users.map((user, index) => {
+            {users.map((user) => (
+              <DisplayUser
+                key={user.pubkey}
+                meta={meta}
+                user={user}
+                metadata={metadata}
+                signedBy={signedBy}
+                nextSigner={nextSigner}
+                getPrevSignersSig={getPrevSignersSig}
+              />
+            ))}
+          </TableBody>
+        </Table>
+      </ListItem>
+    </List>
+  )
+}
+
+enum PrevSignatureValidationEnum {
+  Pending,
+  Valid,
+  Invalid
+}
+
+enum UserStatus {
+  Viewer = 'Viewer',
+  Awaiting = 'Awaiting Signature',
+  Signed = 'Signed',
+  Pending = 'Pending'
+}
+
+type DisplayUserProps = {
+  meta: Meta
+  user: User
+  metadata: { [key: string]: ProfileMetadata }
+  signedBy: `npub1${string}`[]
+  nextSigner?: string
+  getPrevSignersSig: (usersNpub: string) => string | null
+}
+
+const DisplayUser = ({
+  meta,
+  user,
+  metadata,
+  signedBy,
+  nextSigner,
+  getPrevSignersSig
+}: DisplayUserProps) => {
+  const theme = useTheme()
+
   const userMeta = metadata[user.pubkey]
+  const [userStatus, setUserStatus] = useState<UserStatus>(UserStatus.Pending)
+  const [prevSignatureStatus, setPreviousSignatureStatus] =
+    useState<PrevSignatureValidationEnum>(PrevSignatureValidationEnum.Pending)
 
-              let signedStatus = '-'
+  useEffect(() => {
+    if (user.role === UserRole.viewer) {
+      setUserStatus(UserStatus.Viewer)
+      return
+    }
 
-              if (user.role === UserRole.signer) {
     // check if user has signed the document
     const usersNpub = hexToNpub(user.pubkey)
     if (signedBy.includes(usersNpub)) {
-                  signedStatus = 'Signed'
+      setUserStatus(UserStatus.Signed)
-                }
+      return
-                // check if user is the next signer
-                else if (user.pubkey === nextSigner) {
-                  signedStatus = 'Awaiting Signature'
-                }
     }
 
+    // check if user is the next signer
+    if (user.pubkey === nextSigner) {
+      setUserStatus(UserStatus.Awaiting)
+      return
+    }
+  }, [user, nextSigner, signedBy])
+
+  useEffect(() => {
+    const validatePrevSignature = async () => {
+      const handleNullCase = () => {
+        setPreviousSignatureStatus(PrevSignatureValidationEnum.Invalid)
+        return
+      }
+
+      // get previous signers sig from the content of current signers signed event
+      const npub = hexToNpub(user.pubkey)
+      const signedEvent = await parseJson<Event>(
+        meta.docSignatures[npub]
+      ).catch((err) => {
+        console.log(`err in parsing the singed event for ${npub}:>> `, err)
+        toast.error(
+          err.message ||
+            'error occurred in parsing the signed event signature event'
+        )
+        return null
+      })
+
+      if (!signedEvent) return handleNullCase()
+
+      // now that we have signed event of current signer, we'll extract prevSig from its content
+      const parsedContent = await parseJson<SignedEventContent>(
+        signedEvent.content
+      ).catch((err) => {
+        console.log(
+          `an error occurred in parsing the content of signedEvent of ${npub}`,
+          err
+        )
+        toast.error(
+          err.message ||
+            `an error occurred in parsing the content of signedEvent of ${npub}`
+        )
+        return null
+      })
+
+      if (!parsedContent) return handleNullCase()
+
+      const prevSignersSignature = getPrevSignersSig(npub)
+
+      if (!prevSignersSignature) return handleNullCase()
+
+      setPreviousSignatureStatus(
+        parsedContent.prevSig === prevSignersSignature
+          ? PrevSignatureValidationEnum.Valid
+          : PrevSignatureValidationEnum.Invalid
+      )
+    }
+
+    if (userStatus === UserStatus.Signed) {
+      validatePrevSignature()
+    }
+  }, [userStatus, meta.docSignatures, user.pubkey, getPrevSignersSig])
+
   return (
-                <TableRow key={index}>
+    <TableRow>
       <TableCell className={styles.tableCell}>
         <UserComponent
           pubkey={user.pubkey}
@@ -839,16 +1036,34 @@ const DisplayMeta = ({
           image={userMeta?.picture}
         />
       </TableCell>
-                  <TableCell className={styles.tableCell}>
+      <TableCell className={styles.tableCell}>{user.role}</TableCell>
-                    {user.role}
+      <TableCell>
+        <Box sx={{ display: 'flex', alignItems: 'center', gap: '10px' }}>
+          <Typography component="label">{userStatus}</Typography>
+          {userStatus === UserStatus.Signed && (
+            <>
+              {prevSignatureStatus === PrevSignatureValidationEnum.Valid && (
+                <Tooltip title="Contains valid signature of prev signer" arrow>
+                  <CheckCircle sx={{ color: theme.palette.success.light }} />
+                </Tooltip>
+              )}
+              {prevSignatureStatus === PrevSignatureValidationEnum.Invalid && (
+                <Tooltip
+                  title="Contains invalid signature of prev signer"
+                  arrow
+                >
+                  <Cancel sx={{ color: theme.palette.error.main }} />
+                </Tooltip>
+              )}
+            </>
+          )}
+          {userStatus === UserStatus.Awaiting && (
+            <Tooltip title="Waiting for user's sign" arrow>
+              <HourglassTop />
+            </Tooltip>
+          )}
+        </Box>
       </TableCell>
-                  <TableCell>{signedStatus}</TableCell>
     </TableRow>
   )
-            })}
-          </TableBody>
-        </Table>
-      </ListItem>
-    </List>
-  )
 }

src/pages/verify/index.tsx

@@ -4,6 +4,7 @@ import {
   List,
   ListItem,
   ListSubheader,
+  Tooltip,
   Typography,
   useTheme
 } from '@mui/material'
@@ -15,7 +16,12 @@ import { toast } from 'react-toastify'
 import { LoadingSpinner } from '../../components/LoadingSpinner'
 import { UserComponent } from '../../components/username'
 import { MetadataController } from '../../controllers'
-import { CreateSignatureEventContent, Meta, ProfileMetadata } from '../../types'
+import {
+  CreateSignatureEventContent,
+  Meta,
+  ProfileMetadata,
+  SignedEventContent
+} from '../../types'
 import {
   getHash,
   hexToNpub,
@@ -25,6 +31,7 @@ import {
   shorten
 } from '../../utils'
 import styles from './style.module.scss'
+import { Cancel, CheckCircle } from '@mui/icons-material'
 
 export const VerifyPage = () => {
   const theme = useTheme()
@@ -208,6 +215,35 @@ export const VerifyPage = () => {
     setIsLoading(false)
   }
 
+  const getPrevSignersSig = (npub: string) => {
+    if (!meta) return null
+
+    // if user is first signer then use creator's signature
+    if (signers[0] === npub) {
+      try {
+        const createSignatureEvent: Event = JSON.parse(meta.createSignature)
+        return createSignatureEvent.sig
+      } catch (error) {
+        return null
+      }
+    }
+
+    // find the index of signer
+    const currentSignerIndex = signers.findIndex((signer) => signer === npub)
+    // return null if could not found user in signer's list
+    if (currentSignerIndex === -1) return null
+    // find prev signer
+    const prevSigner = signers[currentSignerIndex - 1]
+
+    // get the signature of prev signer
+    try {
+      const prevSignersEvent: Event = JSON.parse(meta.docSignatures[prevSigner])
+      return prevSignersEvent.sig
+    } catch (error) {
+      return null
+    }
+  }
+
   const displayUser = (pubkey: string, verifySignature = false) => {
     const profile = metadata[pubkey]
 
@@ -219,7 +255,27 @@ export const VerifyPage = () => {
       if (signedEventString) {
         try {
           const signedEvent = JSON.parse(signedEventString)
-          isValidSignature = verifyEvent(signedEvent)
+          const isVerifiedEvent = verifyEvent(signedEvent)
+
+          if (isVerifiedEvent) {
+            // get the actual signature of prev signer
+            const prevSignersSig = getPrevSignersSig(npub)
+
+            // get the signature of prev signer from the content of current signers signedEvent
+
+            try {
+              const obj: SignedEventContent = JSON.parse(signedEvent.content)
+              if (
+                obj.prevSig &&
+                prevSignersSig &&
+                obj.prevSig === prevSignersSig
+              ) {
+                isValidSignature = true
+              }
+            } catch (error) {
+              isValidSignature = false
+            }
+          }
         } catch (error) {
           console.error(
             `An error occurred in parsing and verifying the signature event for ${pubkey}`,
@@ -240,16 +296,19 @@ export const VerifyPage = () => {
         />
 
         {verifySignature && (
-          <Typography
+          <>
-            component="label"
+            {isValidSignature && (
-            sx={{
+              <Tooltip title="Valid signature">
-              color: isValidSignature
+                <CheckCircle sx={{ color: theme.palette.success.light }} />
-                ? theme.palette.success.light
+              </Tooltip>
-                : theme.palette.error.main
+            )}
-            }}
+
-          >
+            {!isValidSignature && (
-            {isValidSignature ? 'Valid' : 'Invalid'} Signature
+              <Tooltip title="Invalid signature">
-          </Typography>
+                <Cancel sx={{ color: theme.palette.error.main }} />
+              </Tooltip>
+            )}
+          </>
         )}
       </>
     )
@@ -425,16 +484,20 @@ export const VerifyPage = () => {
                           >
                             {filename}
                           </Typography>
-                          <Typography
+                          {isValidHash && (
-                            component="label"
+                            <Tooltip title="File integrity check passed" arrow>
-                            sx={{
+                              <CheckCircle
-                              color: isValidHash
+                                sx={{ color: theme.palette.success.light }}
-                                ? theme.palette.success.light
+                              />
-                                : theme.palette.error.main
+                            </Tooltip>
-                            }}
+                          )}
-                          >
+                          {!isValidHash && (
-                            {isValidHash ? 'Valid' : 'Invalid'} hash
+                            <Tooltip title="File integrity check failed" arrow>
-                          </Typography>
+                              <Cancel
+                                sx={{ color: theme.palette.error.main }}
+                              />
+                            </Tooltip>
+                          )}
                         </Box>
                       )
                     }

src/types/core.ts

@@ -19,3 +19,7 @@ export interface CreateSignatureEventContent {
   viewers: `npub1${string}`[]
   fileHashes: { [key: string]: string }
 }
+
+export interface SignedEventContent {
+  prevSig: string
+}