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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD
#include "typo.h"
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
// Assume QWERTY layout for now
static const int8_t key_coords[UCHAR_MAX + 1][3] = {
['`'] = { 0, 0, 0},
['~'] = { 0, 0, 1},
['1'] = { 3, 0, 0},
['!'] = { 3, 0, 1},
['2'] = { 6, 0, 0},
['@'] = { 6, 0, 1},
['3'] = { 9, 0, 0},
['#'] = { 9, 0, 1},
['4'] = {12, 0, 0},
['$'] = {12, 0, 1},
['5'] = {15, 0, 0},
['%'] = {15, 0, 1},
['6'] = {18, 0, 0},
['^'] = {18, 0, 1},
['7'] = {21, 0, 0},
['&'] = {21, 0, 1},
['8'] = {24, 0, 0},
['*'] = {24, 0, 1},
['9'] = {27, 0, 0},
['('] = {27, 0, 1},
['0'] = {30, 0, 0},
[')'] = {30, 0, 1},
['-'] = {33, 0, 0},
['_'] = {33, 0, 1},
['='] = {36, 0, 0},
['+'] = {36, 0, 1},
['\t'] = { 1, 3, 0},
['q'] = { 4, 3, 0},
['Q'] = { 4, 3, 1},
['w'] = { 7, 3, 0},
['W'] = { 7, 3, 1},
['e'] = {10, 3, 0},
['E'] = {10, 3, 1},
['r'] = {13, 3, 0},
['R'] = {13, 3, 1},
['t'] = {16, 3, 0},
['T'] = {16, 3, 1},
['y'] = {19, 3, 0},
['Y'] = {19, 3, 1},
['u'] = {22, 3, 0},
['U'] = {22, 3, 1},
['i'] = {25, 3, 0},
['I'] = {25, 3, 1},
['o'] = {28, 3, 0},
['O'] = {28, 3, 1},
['p'] = {31, 3, 0},
['P'] = {31, 3, 1},
['['] = {34, 3, 0},
['{'] = {34, 3, 1},
[']'] = {37, 3, 0},
['}'] = {37, 3, 1},
['\\'] = {40, 3, 0},
['|'] = {40, 3, 1},
['a'] = { 5, 6, 0},
['A'] = { 5, 6, 1},
['s'] = { 8, 6, 0},
['S'] = { 8, 6, 1},
['d'] = {11, 6, 0},
['D'] = {11, 6, 1},
['f'] = {14, 6, 0},
['F'] = {14, 6, 1},
['g'] = {17, 6, 0},
['G'] = {17, 6, 1},
['h'] = {20, 6, 0},
['H'] = {20, 6, 1},
['j'] = {23, 6, 0},
['J'] = {23, 6, 1},
['k'] = {26, 6, 0},
['K'] = {26, 6, 1},
['l'] = {29, 6, 0},
['L'] = {29, 6, 1},
[';'] = {32, 6, 0},
[':'] = {32, 6, 1},
['\''] = {35, 6, 0},
['"'] = {35, 6, 1},
['\n'] = {38, 6, 0},
['z'] = { 6, 9, 0},
['Z'] = { 6, 9, 1},
['x'] = { 9, 9, 0},
['X'] = { 9, 9, 1},
['c'] = {12, 9, 0},
['C'] = {12, 9, 1},
['v'] = {15, 9, 0},
['V'] = {15, 9, 1},
['b'] = {18, 9, 0},
['B'] = {18, 9, 1},
['n'] = {21, 9, 0},
['N'] = {21, 9, 1},
['m'] = {24, 9, 0},
['M'] = {24, 9, 1},
[','] = {27, 9, 0},
['<'] = {27, 9, 1},
['.'] = {30, 9, 0},
['>'] = {30, 9, 1},
['/'] = {33, 9, 0},
['?'] = {33, 9, 1},
[' '] = {18, 12, 0},
};
static int char_distance(char a, char b) {
const int8_t *ac = key_coords[(unsigned char)a], *bc = key_coords[(unsigned char)b];
int ret = 0;
for (int i = 0; i < 3; ++i) {
ret += abs(ac[i] - bc[i]);
}
return ret;
}
int typo_distance(const char *actual, const char *expected) {
// This is the Wagner-Fischer algorithm for Levenshtein distance, using
// Manhattan distance on the keyboard for individual characters.
const int insert_cost = 12;
size_t rows = strlen(actual) + 1;
size_t cols = strlen(expected) + 1;
int arr0[cols], arr1[cols];
int *row0 = arr0, *row1 = arr1;
for (size_t j = 0; j < cols; ++j) {
row0[j] = insert_cost * j;
}
for (size_t i = 1; i < rows; ++i) {
row1[0] = row0[0] + insert_cost;
char a = actual[i - 1];
for (size_t j = 1; j < cols; ++j) {
char b = expected[j - 1];
int cost = row0[j - 1] + char_distance(a, b);
int del_cost = row0[j] + insert_cost;
if (del_cost < cost) {
cost = del_cost;
}
int ins_cost = row1[j - 1] + insert_cost;
if (ins_cost < cost) {
cost = ins_cost;
}
row1[j] = cost;
}
int *tmp = row0;
row0 = row1;
row1 = tmp;
}
return row0[cols - 1];
}
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