/*
    functions.c
    Jeff Ondich, 26 April 2019
    Part of a quick intro to C

    This variant of functions.c is used in our very short intro to lldb.
*/
#include <stdio.h>
#include <string.h>

int fibonacci(int n);
int factorialRecursive(int n);
void squashCharacterInString(char character, char *string);
void makeTrouble();

int main() {
    // Fibonacci
    int n = 10;
    int result = fibonacci(n);
    printf("Fibonacci number %d = %d\n", n, result);

    // Some recursion
    n = 6;
    result = factorialRecursive(n);
    printf("%d! = %d\n", n, result);

    // Some string manipulation
    char word[20];
    strcpy(word, "Mississippi");
    char character = 'i';
    squashCharacterInString(character, word);
    printf("Squashed string: %s\n", word);

    // An opportunity for mischief
    makeTrouble("dog", "cat");

    return 0;
}

// Returns the nth Fibonacci number. Assumes that the Fibonacci
// numbers start at index 0, so fib0 = 1, fib1 = 1, fib2 = 2, etc.
int fibonacci(int n) {
    int previous = 1;
    int current = 1;
    for (int k = 1; k <= n; k++) {
        int new = current + previous;
        previous = current;
        current = new;
    }
    return current;
}

int factorialRecursive(int n) {
    if (n <= 1) {
        return 1;
    }
    int previousFactorial = factorialRecursive(n - 1);
    return previousFactorial * n;
}

// Replaces each occurrence of the specified character with an underscore
// inside the specified string.
void squashCharacterInString(char character, char *s) {
    int n = 0;
    for (int k = 0; s[k] != '\0'; k++) {
        if (s[k] == character) {
            s[k] = '_';
        }
    }
}

void makeTrouble(const char *s1, const char *s2) {
    int a = 5;
    char string1[8];
    int b = 6;
    char string2[8];
    int c = 7;

    strcpy(string1, s1);
    strcpy(string2, s2);

    printf("\n==== makeTrouble ====\n");
    printf("a = %d\n", a);
    printf("string1 = %s\n", string1);
    printf("b = %d\n", b);
    printf("string2 = %s\n", string2);
    printf("c = %d\n", c);
    printf("\n");
}