#ifndef _STRING_HEADER
#define _STRING_HEADER 1


#include <assert.h>
#include <ctype.h>

#include "logging.h"


#define HTTP_STR_TO_VIEW(http_str) ((string_view){(char*)http_str.buf, (size_t)http_str.len})


typedef struct string_s {
    char* buf;
    size_t len;
    size_t size;
} *string;

typedef struct string_view_s {
    char* buf;
    size_t len;
} string_view;

const size_t po2s[] = { 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384 };


size_t find_next_size(size_t old_size) {
    if (old_size >= 16384) {
        return (old_size / 16384 + 1) * 16384;
    } else {
        for(size_t i = 0; i < sizeof(po2s)/sizeof(size_t); ++i) {
            if (old_size < po2s[i]) {
                return po2s[i];
            }
        }
        assert(false /*can not reach here */);
    }
}

string string_init(size_t size) {
    size_t actual_size = find_next_size(size);
    string str = malloc(sizeof (struct string_s));
    assert(str != NULL /* str allocation was successful */);
    str->len = 0;
    str->size = actual_size;
    str->buf = malloc(actual_size);
    assert(str->buf != NULL /* str->buf allocation was successful */);
    return str;
}

string string_from(const char * content) {
    size_t length = strlen(content);
    size_t size = find_next_size(length);
    string str = string_init(size);
    memcpy(str->buf, content, length);
    str->len = length;
    return str;
}

void string_free(string str) {
    free(str->buf);
    free(str);
}

void string_grow(string str, size_t amount) {
    size_t new_size = find_next_size(str->size + amount);
    str->buf = realloc(str->buf, new_size);
    assert(str->buf != NULL /* str->buf reallocation was successful */);
    str->size = new_size;
}

void string_append_with_len(string str, const char * content, size_t len) {
    if (str->len + len + 1 > str->size) {
        string_grow(str, len + 1);
    }
    assert(str->len + len <= str->size /* string is large enough to fit appended content */);
    memcpy(str->buf + str->len, content, len);
    str->len += len;
}

void string_append(string str, const char * content) {
    size_t len = strlen(content);
    string_append_with_len(str, content, len);
}

void string_append_char(string str, char ch) {
    string_append_with_len(str, &ch, 1);
}

void string_concat(string str, const string_view *other) {
    string_append_with_len(str, other->buf, other->len);
}

void string_copy(string str, const string_view *other) {
    str->len = 0;
    string_concat(str, other);
}

void string_copy_chars(string str, const char *other) {
    str->len = 0;
    string_append(str, other);
}

void string_null_terminate(string str) {
    if (str->len + 1 > str->size) {
        string_grow(str, 1);
    }
    assert(str->len + 1 <= str->size /* string is large enough to fit null terminator at the end */);
    str->buf[str->len] = '\0';
}

string_view string_get_view(string_view *str, size_t offset, int length) {
    string_view view;
    if (length == -1) {
        length = str->len - offset;
    }
    if (offset < str->len && offset + length - 1 < str->len) {
        view.buf = str->buf + offset;
        view.len = length;
    } else {
        view.buf = str->buf + str->len - 1;
        view.len = 0;
    }
    return view;
}

size_t string_split(string_view *str, char delimiter, string_view **out) {
    const char* strPtr = str->buf;
    size_t remainingLength = str->len;
    const char* newlinePtr;
    
    string_view *lines = malloc(sizeof(string_view));
    assert(lines != NULL /* lines allocation was successful */);
    int nextLineIndex = 0;
    size_t offset, length;
    
    while(NULL != (newlinePtr = memchr(strPtr, delimiter, remainingLength))) {
        offset = strPtr - str->buf;
        length = newlinePtr - strPtr;
        lines[nextLineIndex] = string_get_view(str, offset, length);
        nextLineIndex += 1;
        strPtr = newlinePtr + 1;
        remainingLength -= length + 1;
        lines = realloc(lines, sizeof(string_view) * (nextLineIndex + 1));
        assert(lines != NULL /* lines allocation was successful */);
    }
    offset = strPtr - str->buf;
    lines[nextLineIndex] = string_get_view(str, offset, -1);
    
    *out = lines;
    
    return nextLineIndex + 1;
}

bool string_is_whitespace(string_view *str) {
    for (size_t i = 0; i < str->len; ++i) {
        char ch = str->buf[i];
        if (!isspace(ch)) return false;
    }
    return true;
}


int hex_char_to_num(char ch) {
    if (ch >= '0' && ch <= '9') {
        return ch - '0';
    }
    if (ch >= 'a' && ch <= 'f') {
        return ch - 'a' + 10;
    }
    if (ch >= 'A' && ch <= 'F') {
        return ch - 'A' + 10;
    }
    return -1;
}

int decode_url_hex(const char * input) {
    char ch1 = input[0];
    char ch2 = input[1];
    int n1 = hex_char_to_num(ch1);
    int n2 = hex_char_to_num(ch2);
    if (n1 == -1 || n2 == -1) {
        return -1;
    } else {
        return n1 * 16 + n2;
    }
}
 
string string_urldecode(string_view *str) {
    string result = string_init(str->len);
    
    int c;
    
    for(size_t i = 0; i < str->len; ++i) {
        c = str->buf[i];
        if (c == '+') {
            c = ' ';
        } else if (c == '%') {
            if (i + 2 < str->len) {
                c = decode_url_hex(&(str->buf[i + 1]));
                i += 2;
                if (c == -1) {
                    goto error;
                }
            } else {
                goto error;
            }
        }
        string_append_char(result, (char)c);
    }
    return result;
    
    error:
        string_free(result);
        return NULL;
}



#endif