Preserve visibility of users' votes across page refresh

[voter] / src / main.rs
diff --git a/src/main.rs b/src/main.rs

index 5c4ad9095733785c0f2f0bf936447ffdca5de97e..61875d6de16d412d40ef12c2129524ab438c5a58 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
  use rand::prelude::*;
+use std::collections::{HashMap, HashSet};
  use std::io::prelude::*;
  use std::path::{Path, PathBuf};
  
@@ -44,6 +45,31 @@ fn get_voter(request: &cgi::Request) -> Result<&[u8], cgi::Response> {
      }
  }
  
+fn tally_votes(dir: PathBuf) -> std::io::Result<HashMap<String, HashSet<String>>> {
+    let mut tally: HashMap<String, HashSet<String>> = HashMap::new();
+    let vfile = std::fs::File::open(dir.join("votes"))?;
+    for liner in std::io::BufReader::new(vfile).lines() {
+        let line = liner?;
+        if let Some((voter, datum)) = line.split_once(' ') {
+            if voter.len() == COOKIE_LENGTH {
+                if let Some((vote, candidate)) = datum.split_once(' ') {
+                    if vote == "0" {
+                        if let Some(entry) = tally.get_mut(candidate) {
+                            entry.remove(voter);
+                        }
+                    } else if vote == "1" {
+                        tally
+                            .entry(candidate.to_owned())
+                            .or_default()
+                            .insert(voter.to_owned());
+                    }
+                }
+            }
+        }
+    }
+    Ok(tally)
+}
+
  fn make_random_id() -> [u8; COOKIE_LENGTH] {
      let mut id = [0; COOKIE_LENGTH];
      for i in 0..COOKIE_LENGTH {
@@ -97,6 +123,18 @@ const HTML_HEADER: &str = "<!DOCTYPE html>
                const spin = document.createElement('div')
                spin.appendChild(document.createTextNode('⏳'))
                cb.parentElement.insertBefore(spin, cb)
+
+              const req = new XMLHttpRequest()
+              req.addEventListener('load', function(e) {
+                cb.parentElement.removeChild(cb.previousElementSibling)
+                if (req.status == 200) {
+                    cb.style.display = ''
+                } else {
+                   cb.parentElement.insertBefore(document.createTextNode('❗'), cb)
+                }
+              })
+              req.open('PUT', window.location.href)
+              req.send((cb.checked ? 1 : 0) + ' ' + cb.parentElement.nextElementSibling.innerHTML)
              }
            })(cb))
            cb.disabled = false
@@ -111,8 +149,22 @@ const HTML_FOOTER: &str = "
    </body>
  </html>";
  
+fn supports(tally: &HashMap<String, HashSet<String>>, me: &str, candidate: &str) -> bool {
+    tally
+        .get(candidate)
+        .map(|supporters| supporters.contains(me))
+        .unwrap_or(false)
+}
+
  fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response, cgi::Response> {
      let voter = get_voter(&request);
+    let me = if let Ok(id) = voter {
+        std::str::from_utf8(id).ok()
+    } else {
+        None
+    };
+    let tally =
+        tally_votes(dir.clone()).map_err(|_| cgi::text_response(503, "Couldn't tally votes"))?;
      let cfile = std::fs::File::open(dir.join("candidates"))
          .map_err(|_| cgi::text_response(503, "No candidates"))?;
      let mut response = cgi::html_response(
@@ -120,7 +172,17 @@ fn prompt_for_vote(dir: PathBuf, request: cgi::Request) -> Result<cgi::Response,
          std::iter::once(Ok(HTML_HEADER.to_owned()))
              .chain(std::io::BufReader::new(cfile).lines().map(|rc| {
                  rc.map(|c| {
-                    format!("<tr><td><input type=\"checkbox\" disabled></td><td>{c}</td></tr>")
+                    let checked = if me.map(|me| supports(&tally, me, &c)).unwrap_or(false) {
+                        "checked"
+                    } else {
+                        ""
+                    };
+                    format!(
+                        "<tr>
+                        <td><input type=\"checkbox\" autocomplete=\"off\" {checked} disabled></td>
+                        <td>{c}</td>
+                        </tr>"
+                    )
                  })
              }))
              .chain(std::iter::once(Ok(HTML_FOOTER.to_owned())))