#include <stdio.h>
#include "buf.h"
#include <string.h>
#include <stdlib.h>

typedef enum {
    false,
    true
} bool;

FILE* getfile(int argc, char** argv){
    if (argc >= 2)
        return fopen(argv[1], "r");
    else
        return stdin;
}

char* chrmult(char c, size_t ct){
    char* str = malloc(sizeof(char)*(ct+1)); str[ct] = 0;
    memset(str, c, ct); 
    return str;
}

// file read & buffer fill helpers

FILE* in;
buf* inbuf;

int addchr(void){
    int c = fgetc(in);
    if (c != EOF) inschrbuf(inbuf, c);
    return c;
}

size_t fillbuf(size_t len){ // returns real len
    int c;
    size_t set;
    for (set = buflen(inbuf); set < len && (c = addchr()) != EOF;set++);
    return set;
}

size_t chrfill(char chr){
    size_t len = buflen(inbuf);
    char* str = peekstrbuf(inbuf, 0, len);
    size_t line;
    for (line = 0; line < len; line++)
        if (str[line] == chr) return line+1;
    for (int c = 0; c != chr && (c = addchr()) != EOF; line++);
    return line;
}

#define min(a,b) a < b ? a : b

size_t chrnfill(char chr, size_t sz){//fills to first of chr or sz
    size_t len = buflen(inbuf);
    size_t lim = min(len,sz);
    char* str = peekstrbuf(inbuf, 0, lim);
    size_t line;
    for (line = 0; line < lim; line++)
        if (str[line] == chr) return line+1;
    free(str);
    for (int c = 0; c != chr && (c = addchr()) != EOF
    && line<sz; line++);
    return line;
}

// typesetting config and commands to change.
int width = 80;
bool brk = false; // not implemented

char* center(char* txt){
    size_t len = strlen(txt);
    int max = width/2 + len/2; // excluding terminator
    int min = max-len+1; // first index of *txt
    char* str = malloc(sizeof(char)*(max + 2));
    memset(str, ' ', min);
    memcpy(str+min, txt, len);
    str[max] = '\n';
    str[max+1] = 0;
    return str;
}
char* setwidth(char* txt){
    sscanf(txt, "%d", &width);
    return NULL;
}

char* cmds[] = {"CT ", "W "};
char* (*call[])(char* txt) = {center, setwidth};

char* cmd(void){
    char* dat = popstrbuf(inbuf, chrfill('\n'));
    size_t low = 0; size_t high = sizeof(cmds)/sizeof(*cmds); //len
    while (high >= low){
        int mid = ((unsigned int)low + (unsigned int)high) >> 1;
        char* mval = cmds[mid];

        int cmp = strncmp(dat, mval, strlen(mval));
        if (cmp < 0) // dat < mval
            high = mid - 1;
        else if (cmp > 0)
            low = mid + 1;
        else
            return call[mid](dat+strlen(mval));
    }
    free(dat);
    return NULL;
}

// normal typesetting 

bool cont_typst = false; // communicates with line() for broken lines.

size_t nextws(size_t start){//searches for \n or [^ \n]-1 in buffer
    //starts at `start` (if not whitespace, returns start-1)
    size_t len = buflen(inbuf);
    char* str = peekstrbuf(inbuf, start, len-start);
    size_t i;
    for (i = 0; i<len-start; i++){
        if (str[i] == '\n') return start+i;
        if (str[i] != ' ') return start+i-1;
    }
    free(str);
    for (int c = 0; c != '\n' && ( c = addchr() ) != EOF && c == ' ';
    len++); // if this is a newline, exit late (len is last, !(len-1)).
    return len;
}

char* typeset(void){ // brk is completely unimplemented
    size_t len = chrnfill('\n', width+1); //+1 for \n on 81-char lines
    char* next = peekstrbuf(inbuf, 0, len);
    size_t wsend = 0;
    if (next[--len] == '\n') wsend = len;
    if (next[len] == ' ') wsend = nextws(len);
    for (; next[len] == ' ' && wsend; len--){
        if (!wsend && next[len] == ' ') wsend = len;
    } // len should be last letter
    if (peekchrbuf(inbuf, wsend) == '\n') cont_typst = false;
    else cont_typst = true;
    free(next);
    char* ln = popstrbuf(inbuf, wsend+1); ln[len] = '\n'; ln[len+1] = 0;
    return ln;
}

// a parser to choose when to typeset and when to run a command

char* line(void){
    size_t sz;
    if ( (sz = fillbuf(2)) == 0)
        return "";
    char* twobytes = peekstrbuf(inbuf, 0, 2); // .., .\n, or ^.?
    if (sz == 1 || twobytes[1] == '\n' || cont_typst) return typeset();
    if (twobytes[0] == '.') popchrbuf(inbuf);
    if (twobytes[0] == '.' && twobytes[1] != '.'){
        char* data = cmd();
        if (data) return data;
        return line();
    } else {
        return typeset();
    }
}

// orchestration

int main(int argc, char** argv){
    int c;
    in = getfile(argc, argv);
    inbuf = newbuf(256);
    if (in == NULL){
        perror(argv[1]);
        return 1;
    }
    char* out;
    while ( (out = line())[0] != '\0'){
        printf("%s",out);
    }
    fclose(in);
    return 0;
}