From 723aea0582ff6905c9eebbe8d724d7b1a1d44cf1 Mon Sep 17 00:00:00 2001
From: Adrian Cochrane <adrian@openwork.nz>
Date: Sun, 18 Oct 2020 11:58:58 +1300
Subject: [PATCH] Prepare for navigating links:

Compute levenshtein distances.
Read lines from stdin.
---
 src/main.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 84 insertions(+), 10 deletions(-)

diff --git a/src/main.c b/src/main.c
index b02f35f..1dc3928 100644
--- a/src/main.c
+++ b/src/main.c
@@ -4,6 +4,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <termios.h>
+#include <limits.h>
 
 #include "HsFFI.h"
 #include <espeak-ng/espeak_ng.h>
@@ -135,15 +136,80 @@ void speak(char *ssml, char *mark, char* fallback) {
         espeak_Synth_Mark(ssml, strlen(ssml)+1, fallback, 0, flags, NULL, NULL);
     else espeak_Synth(ssml, strlen(ssml)+1, 0, POS_CHARACTER, 0, flags, NULL, NULL);
 }
+
+/* Utilities */
+#define SWAP(type, a, b) {type temp = a; a = b; b = temp;}
+int min(int a, int b) {return a < b ? a : b;}
+
+/* Keyboard input */
+int levenshtein_distance(const char *a, const char* b) {
+    int a_len = strlen(a);
+    int b_len = strlen(b);
+    if (a_len < b_len) {
+        SWAP(int, a_len, b_len);
+        SWAP(const char*, a, b);
+    }
+    int *v0 = malloc(sizeof(int)*b_len);
+    int *v1 = malloc(sizeof(int)*b_len);
+
+    // Initialize v0 for an edit distance of an empty a
+    for (int i = 0; i < b_len; i++) v0[i] = i;
+
+    // The core algorithm
+    for (int i = 0; i < a_len; i++) {
+        // Edit distance from empty string is delete i characters.
+        v1[0] = i;
+
+        for (int j = 0; j < b_len - 1; j++) {
+            int deletion_cost = v0[j+1] + 1; // above cell + deletion
+            int insertion_cost = v1[j] + 1; // left cell + insertion
+            // top left cell + maybe substitution
+            int substitution_cost = v0[j] + (a[i] == b[j] ? 0 : 1);
+
+            v1[j+1] = min(deletion_cost, min(insertion_cost, substitution_cost));
+        }
+
+        // Progress to next row
+        SWAP(int*, v0, v1);
+    }
+    return v0[b_len-1];
+}
+
+int MAX_DIST = 3; // Is this ideal?
+char *select_link(char **links, char *command) {
+    // Pass 1, min distance
+    int score = INT_MAX;
+    for (int i = 0; strcmp(links[i], " ") != 0; i++)
+        score = min(score, levenshtein_distance(command, links[i]));
+
+    // Pass 2: Is ambiguous?
+    int is_ambiguous = 0;
+    for (int i = 0; strcmp(links[i], " ") != 0; i++)
+        is_ambiguous |= score >= levenshtein_distance(command, links[i]) - MAX_DIST;
+
+    // Pass 3: Retrieve answer
+    for (int i = 0; strcmp(links[i], " ") != 0; i += 3) {
+        if (score < levenshtein_distance(command, links[i]) &&
+            score < levenshtein_distance(command, links[i+1]) &&
+            score < levenshtein_distance(command, links[i+2])) continue;
+        if (!is_ambiguous) return links[i+2];
+
+        // TODO Apply formatting!
+        speak(links[i+2], NULL, NULL); speak(links[i], NULL, NULL); speak(links[i+1], NULL, NULL); 
+    }
+
+    return "";
+}
+
+struct termios stored_settings, no_echo;
 int read_keyboard = 0;
 int speak_finalize(char *ssml) {
     while (read_keyboard) {
-        char c = getc(stdin);
-        if (c == '\033') {
+        if (getc(stdin) == '\033') {
             char mark[200];
             char fallback[200];
             espeak_Cancel();
-            c = getc(stdin);
+            char c = getc(stdin);
             if (c == 0 || c == -1 || c == '\033' || c == 'q') goto close; // skip [
             switch (getc(stdin)) {
             case 'A':
@@ -201,6 +267,15 @@ int speak_finalize(char *ssml) {
                 speak(ssml, paragraph_no > 0 ? mark : NULL, NULL);
                 break;
             }
+        } else {
+            // Read in a line
+            tcsetattr(0, TCSANOW, &stored_settings);
+            char *line = NULL;
+            size_t len = 0;
+            if (getline(&line, &len, stdin) < 0) {
+                fprintf(stderr, "Failed to read stdin line!\n");
+            } else printf("%s\n", line); // TODO Do something with this!
+            tcsetattr(0, TCSANOW, &no_echo);
         }
     }
     espeak_ng_STATUS result = espeak_ng_Synchronize();
@@ -232,7 +307,6 @@ FILE *parse_opt_file() {
     return ret;
 }
 
-struct termios stored_settings;
 int main(int argc, char **argv) {
     int speak_err = 0;
     hs_init(&argc, &argv);
@@ -270,12 +344,12 @@ int main(int argc, char **argv) {
         case 'k':
             read_keyboard = 1;
             // Read input character by character, not line by line.
-            struct termios new_settings = stored_settings;
-            new_settings.c_lflag &= (~ICANON);
-            new_settings.c_lflag &= (~ECHO);
-            new_settings.c_cc[VTIME] = 1;
-            new_settings.c_cc[VMIN] = 0;
-            tcsetattr(0, TCSANOW, &new_settings);
+            no_echo = stored_settings;
+            no_echo.c_lflag &= (~ICANON);
+            no_echo.c_lflag &= (~ECHO);
+            no_echo.c_cc[VTIME] = 1;
+            no_echo.c_cc[VMIN] = 0;
+            tcsetattr(0, TCSANOW, &no_echo);
             break;
         case 'w':
             use_espeak = 1;
-- 
2.30.2