#include "tstring.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

int GetGlyphByteWidth(const char* glyph);
void TStringCopyGlyph(const char* glyph, int length, TString* string);
int ResizeTStringCapacity(int newTextLength, TString* string);

struct __tstring {
    char* Characters;
    int Length;
    int ByteCount;
    int Capacity;
};

TString* TStringCreate(void) {
    TString* string = malloc(sizeof(TString));

    if (!string) {
        fprintf(stderr, "Failed to malloc space for TString. %s.\n", strerror(errno));

        return NULL;
    }

    string->Characters = calloc(DEFAULT_TSTRING_BYTE_BUFFER, sizeof(char));

    if (!string->Characters) {
        fprintf(stderr, "Failed to malloc space for TString character array. %s.\n", strerror(errno));

        free(string);

        return NULL;
    }

    string->Capacity = DEFAULT_TSTRING_BYTE_BUFFER;
    string->ByteCount = 0;
    string->Length = 0;

    return string;
}

int TStringLength(const TString* string) {
    if (!string) return -1;

    return string->Length;
}

int ResizeTStringCapacity(int newTextLength, TString* string) {
    if (!string) return 0;
    if (string->ByteCount + newTextLength < string->Capacity) return 1;
    
    //TODO: This is a bad assumption considering the additional length could overflow without a check.
    char* buffer = realloc(string->Characters, string->Capacity * 2);

    if (!buffer) {
        fprintf(stderr, "Failed to realloc space for text insertion. %s.\n", strerror(errno));

        return 0;
    }

    string->Characters = buffer;
    string->Capacity *= 2;

    return 1;
}

void TStringRemove(int index, TString* string) {

}

void TStringInsertText(const char* text, int index, TString* string) {
    if (!text || !string) return;

    int textLength = strlen(text);
    int glyphCount = 0;
    int startByte = 0;
    
    if (!ResizeTStringCapacity(textLength, string)) return;

    while(startByte < string->ByteCount) {
        if (glyphCount == index) break;

        startByte += GetGlyphByteWidth(&string->Characters[startByte]);
        
        glyphCount++;
    }
}

void TStringMemSwap(const char* text, int startIndex, int length, TString* string) {
    if (!text || !string) return;

    char buffer[256] = { 0 };
    char intermediate[sizeof buffer] = { 0 };
    const char* inputTextStart = text;
    const char* characterListStart = &string->Characters[startIndex];

    int blockCount = length / sizeof buffer;
    int remainder = length % sizeof buffer;

    for(; blockCount > 0; blockCount--) {
        
    }
}

void TStringAppendText(const char* text, TString* string) {
    if (!text || !string) return;

    int totalLength = strlen(text);
    int glyphLength = GetGlyphByteWidth(text);

    //If the two lengths are the same then that means we have a single character.
    //Simply append it to the list and return.
    if (totalLength == glyphLength) {
        TStringCopyGlyph(text, glyphLength, string);

        return;
    }

    //If we've made it here, than that means we have a full on string of characters.
    for(int i = 0; i < totalLength;) {
        TStringCopyGlyph(&text[i], glyphLength, string);

        i += glyphLength;
        glyphLength = GetGlyphByteWidth(&text[i]);
    }
}

char* TStringGetString(const TString* string) {
    if (!string) return NULL;

    char* text = calloc(string->ByteCount + 1, sizeof(char));

    if (!text) {
        fprintf(stderr, "Failed to calloc memory for TString text. %s.\n", strerror(errno));

        return NULL;
    }

    memcpy(text, string->Characters, string->ByteCount);

    return text;
}

void TStringGetGlyph(int index, char buffer[8], const TString* string) {
    if (!buffer || !string) return;

    memset(buffer, '\0', sizeof *buffer);

    int glyphCount = 0;

    for(int i = 0; i < string->ByteCount;) {
        int glyphWidth = GetGlyphByteWidth(&string->Characters[i]);

        if (glyphCount == index) {
            memcpy(buffer, &string->Characters[i], glyphWidth);
            return;
        }

        glyphCount++;
        i += glyphWidth;
    }
}

void TStringFree(TString* string) {
    if (!string) return;

    if (string->Characters) free(string->Characters);

    free(string);
}

int GetGlyphByteWidth(const char* glyph) {
    if (!glyph) return -1;

    if ((*glyph & 0x80) == 0) {
        return 1;
    }
    else if ((*glyph & 0xE0) == 0xC0) {
        return 2;
    }
    else if ((*glyph & 0xF0) == 0xE0) {
        return 3;
    }
    else if ((*glyph & 0xF8) == 0xF0) {
        return 4;
    }

    return -1;
}

void TStringCopyGlyph(const char* glyph, int length, TString* string) {
    if (!glyph || !string) return;
    if (length < 1) return;

    if (!ResizeTStringCapacity(length, string)) return;

    memcpy(&string->Characters[string->ByteCount], glyph, length);

    string->ByteCount += length;
    string->Length++;
}

void TStringPrintDetails(const TString* string) {
    if (!string) return;

    printf("Length: %d Size: %d byte(s) Capacity: %d bytes\n", string->Length, string->ByteCount, string->Capacity);
    
    if (string->Characters) {
        char* text = TStringGetString(string);
        printf("%s\n", text);
        free(text);
    }
}