feat(rust-proxy-engine): add a Rust SIP proxy engine with shared SIP and codec libraries

rust/crates/proxy-engine/src/dtmf.rs

@@ -0,0 +1,200 @@
+//! DTMF detection — parses RFC 2833 telephone-event RTP packets.
+//!
+//! Deduplicates repeated packets (same digit sent multiple times with
+//! increasing duration) and fires once per detected digit.
+//!
+//! Ported from ts/call/dtmf-detector.ts.
+
+use crate::ipc::{emit_event, OutTx};
+
+/// RFC 2833 event ID → character mapping.
+const EVENT_CHARS: &[char] = &[
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '*', '#', 'A', 'B', 'C', 'D',
+];
+
+/// Safety timeout: report digit if no End packet arrives within this many ms.
+const SAFETY_TIMEOUT_MS: u64 = 200;
+
+/// DTMF detector for a single RTP stream.
+pub struct DtmfDetector {
+    /// Negotiated telephone-event payload type (default 101).
+    telephone_event_pt: u8,
+    /// Clock rate for duration calculation (default 8000 Hz).
+    clock_rate: u32,
+    /// Call ID for event emission.
+    call_id: String,
+
+    // Deduplication state.
+    current_event_id: Option<u8>,
+    current_event_ts: Option<u32>,
+    current_event_reported: bool,
+    current_event_duration: u16,
+
+    out_tx: OutTx,
+}
+
+impl DtmfDetector {
+    pub fn new(call_id: String, out_tx: OutTx) -> Self {
+        Self {
+            telephone_event_pt: 101,
+            clock_rate: 8000,
+            call_id,
+            current_event_id: None,
+            current_event_ts: None,
+            current_event_reported: false,
+            current_event_duration: 0,
+            out_tx,
+        }
+    }
+
+    /// Feed an RTP packet. Checks PT; ignores non-DTMF packets.
+    /// Returns Some(digit_char) if a digit was detected.
+    pub fn process_rtp(&mut self, data: &[u8]) -> Option<char> {
+        if data.len() < 16 {
+            return None; // 12-byte header + 4-byte telephone-event minimum
+        }
+
+        let pt = data[1] & 0x7F;
+        if pt != self.telephone_event_pt {
+            return None;
+        }
+
+        let marker = (data[1] & 0x80) != 0;
+        let rtp_timestamp = u32::from_be_bytes([data[4], data[5], data[6], data[7]]);
+
+        // Parse telephone-event payload.
+        let event_id = data[12];
+        let end_bit = (data[13] & 0x80) != 0;
+        let duration = u16::from_be_bytes([data[14], data[15]]);
+
+        if event_id as usize >= EVENT_CHARS.len() {
+            return None;
+        }
+
+        // Detect new event.
+        let is_new = marker
+            || self.current_event_id != Some(event_id)
+            || self.current_event_ts != Some(rtp_timestamp);
+
+        if is_new {
+            // Report pending unreported event.
+            let pending = self.report_pending();
+
+            self.current_event_id = Some(event_id);
+            self.current_event_ts = Some(rtp_timestamp);
+            self.current_event_reported = false;
+            self.current_event_duration = duration;
+
+            if pending.is_some() {
+                return pending;
+            }
+        }
+
+        if duration > self.current_event_duration {
+            self.current_event_duration = duration;
+        }
+
+        // Report on End bit (first time only).
+        if end_bit && !self.current_event_reported {
+            self.current_event_reported = true;
+            let digit = EVENT_CHARS[event_id as usize];
+            let duration_ms = (self.current_event_duration as f64 / self.clock_rate as f64) * 1000.0;
+
+            emit_event(
+                &self.out_tx,
+                "dtmf_digit",
+                serde_json::json!({
+                    "call_id": self.call_id,
+                    "digit": digit.to_string(),
+                    "duration_ms": duration_ms.round() as u32,
+                    "source": "rfc2833",
+                }),
+            );
+
+            return Some(digit);
+        }
+
+        None
+    }
+
+    /// Report a pending unreported event.
+    fn report_pending(&mut self) -> Option<char> {
+        if let Some(event_id) = self.current_event_id {
+            if !self.current_event_reported && (event_id as usize) < EVENT_CHARS.len() {
+                self.current_event_reported = true;
+                let digit = EVENT_CHARS[event_id as usize];
+                let duration_ms =
+                    (self.current_event_duration as f64 / self.clock_rate as f64) * 1000.0;
+
+                emit_event(
+                    &self.out_tx,
+                    "dtmf_digit",
+                    serde_json::json!({
+                        "call_id": self.call_id,
+                        "digit": digit.to_string(),
+                        "duration_ms": duration_ms.round() as u32,
+                        "source": "rfc2833",
+                    }),
+                );
+
+                return Some(digit);
+            }
+        }
+        None
+    }
+
+    /// Process a SIP INFO message body for DTMF.
+    pub fn process_sip_info(&mut self, content_type: &str, body: &str) -> Option<char> {
+        let ct = content_type.to_ascii_lowercase();
+
+        if ct.contains("application/dtmf-relay") {
+            // Format: "Signal= 5\r\nDuration= 160\r\n"
+            let signal = body
+                .lines()
+                .find(|l| l.to_ascii_lowercase().starts_with("signal"))
+                .and_then(|l| l.split('=').nth(1))
+                .map(|s| s.trim().to_string())?;
+
+            if signal.len() != 1 {
+                return None;
+            }
+            let digit = signal.chars().next()?.to_ascii_uppercase();
+            if !"0123456789*#ABCD".contains(digit) {
+                return None;
+            }
+
+            emit_event(
+                &self.out_tx,
+                "dtmf_digit",
+                serde_json::json!({
+                    "call_id": self.call_id,
+                    "digit": digit.to_string(),
+                    "source": "sip-info",
+                }),
+            );
+
+            return Some(digit);
+        }
+
+        if ct.contains("application/dtmf") {
+            let digit = body.trim().chars().next()?.to_ascii_uppercase();
+            if !"0123456789*#ABCD".contains(digit) {
+                return None;
+            }
+
+            emit_event(
+                &self.out_tx,
+                "dtmf_digit",
+                serde_json::json!({
+                    "call_id": self.call_id,
+                    "digit": digit.to_string(),
+                    "source": "sip-info",
+                }),
+            );
+
+            return Some(digit);
+        }
+
+        None
+    }
+}