#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>

#include "buf.h"
#include "sb.h"
#include "ll.h"

static char* line(void);
static char* wordset(char* txt);
static void  wsclean(char* txt);

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

static 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

static FILE* in;
static buf* inbuf;

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

static 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;
}

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

#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);
    char* line = memchr(str, chr, lim);
    free(str);
    if (line) return line-str+1;
    for (int c = 0; c != chr && (c = addchr()) != EOF&& len<sz; len++);
    return len;
}

// typesetting config and commands to change.
static int width = 80;
static char nbsp = 0;

static 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;
}
static char* setwidth(char* txt){
    sscanf(txt, "%d", &width);
    return NULL;
}
static char* fillline(char* txt){
    char* str = malloc(sizeof(char)*(width+2));
    str[width] = '\n'; str[width+1] = 0;
    memset(str, txt[0], width);
    return str;
}
static char* token(char* txt, char c) {
    char* end = strchr(txt, c);
    *end = 0;
    return end+1;
}
static char* leader(char* txt){
    char* start = txt;
    char* repeat = token(start, '|');
    char* end = token(repeat, '|');
    char* fin = malloc(sizeof(char)*(width+2));
    fin[width] = '\n'; fin[width+1] = 0;
    strcpy(fin, start);
    size_t max = width-strlen(end); size_t rptln = strlen(repeat);
    strcpy(fin+max, end);
    for (int i=strlen(start); i<width-strlen(end); i++)
        fin[i] = repeat[i % rptln];
    return fin;
}
static bool endgroup = false;
static llnode* freenext(llnode* node){
    llnode* tmp = node->next;
    node->next = tmp->next;
    free(tmp->str);
    free(tmp);
    if (tmp == node) return NULL;
    return node->next;
}
static void multbreak(sb* buffer, size_t start,
 size_t len, llnode** tail, size_t* ct){
    for (size_t i = *ct; i > 0; i--){
        char* str = (*tail)->next->str + start;
        // tail->next is used so it can be gracefully freed
        if (strlen(str) < len){ // if node is smaller than len,
            insstr(buffer, str); // put the whole thing in the buffer
            // and remove the node, switching to next
            *tail = freenext(*tail);
            (*ct)--;
        } else {
            char tmp = str[len];
            str[len] = 0; // truncate str at max length
            insstr(buffer, str); // insert that
            insstr(buffer, "\n");
            str[len] = tmp; // restore string
            *tail = (*tail)->next; // iter
        }
    }
}
static llnode* accumlines(size_t* ct){ // returns tail of linked list
    llnode *head, *tail; head = tail = appendll(NULL, NULL);
    (*ct) = 0;
    while (!endgroup){
        char* ln = line();
        if (!ln[0]) { // ln == ""
            free(ln);
            break;
        }
        char* next; //greater than nl
        while ( (next = strchr(ln, '\n')) ) {
            next++;
            char sub = *next;
            *next = 0;
            tail = appendll(tail, ln);
            (*ct)++;
            *next = sub;
            ln = next;
        }
    }
    tail->next = head->next; // loop linked list
    free(head);
    endgroup = false; // prevents false positive on next run
    return tail;
}
static char* foldlines(llnode* tail, size_t ct){
    sb* buf = newsb(100);

    size_t oldbrk = 0, brk = 0;
    for (size_t i = 0; tail; i++){ // check every column until all rows
                                   // are removed.
        bool valid = true; // if stays true, this is a space
        bool done = true; // if stays true, all strings are complete
        llnode* orig = tail;
        do { // check every string
            if (!tail->end && tail->str[i] == 0) tail->end = true;
            // ignore strings that have already finished
            else if (!tail->end){
                done = false;
                if (tail->str[i] != ' ') valid = false;
                // can't break here because tail needs to return to orig
            }
            tail = tail->next;
        } while (tail != orig);
        if (valid) brk = i;
        if (done || (!valid && i-oldbrk >= width)){
            // either all strings are done
            // or it has hit a non-space column and accum enough space
            multbreak(buf, oldbrk, brk-oldbrk+1, &tail, &ct);
            oldbrk = brk+1; // tells offset from previous cut
        }
    }

    return decompose(buf);
}
static char* lineset(char* txt){
    size_t ct;
    llnode* tail = accumlines(&ct);
    return foldlines(tail, ct);
}
static char* emptalloc(void){ // need a null string so it can be freed later
    char* str = malloc(sizeof(char)); str[0] = 0;
    return str;
}
static char* fingroup(char* txt){
    endgroup = true;
    return emptalloc();
}
static char* vert(char* txt){
    int ln; sscanf(txt, "%d", &ln);
    return chrmult('\n', ln);
}
static char* nbrkspc(char* txt){
    if (txt[0] == '\n') txt[0] = 0;
    if (txt[1] == '\n') txt[1] = 0;
    if (txt[0] != 0 && txt[1] != 0)
        nbsp = txt[1];
    else if (txt[0] != 0)
        nbsp = txt[0];
    else
        nbsp = 0;
    return NULL;
}
static char* merge(char* txt){ // merges until an endgroup
    // gather lines
    size_t ct;
    llnode* head = accumlines(&ct)->next;
    // count total length (for malloc)
    size_t len = 0;
    for (size_t i = 0; i < ct; i++, head = head->next){
        size_t slen = strlen(head->str)-1;
        head->str[slen] = 0; // remove the nl character at the end
        len += slen; // add the (new) length of string
    }
    char *str, *pos;
    pos = str = malloc(sizeof(char)*(len+2));
    str[len] = '\n'; str[len+1] = 0; // str = "***********\n"
    for (size_t i = 0; i < ct; i++){
        wsclean(head->str);
        size_t slen = strlen(head->str);
        memcpy(pos, head->str, slen);
        pos += slen;
        llnode* tmp = head;
        head = head->next;
        free(tmp->str);
        free(tmp);
    }
    return str;
}

static char* cmds[] = // MUST be sorted alphabetically
    {"CT ", "EG", "FIL ", "LD ", "LS", "MRG", "NBSP", "V ", "W "};
static char* (*call[])(char* txt) =
    {center, fingroup, fillline, leader, lineset, merge, nbrkspc,
    vert, setwidth};

static char* cmd(void){
    char* dat = popstrbuf(inbuf, chrfill('\n'));
    size_t low = 0; size_t high = sizeof(cmds)/sizeof(*cmds); //len
    char* proc = NULL;
    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{
            proc = call[mid](dat+strlen(mval));
            break;
        }
    }
    free(dat);
    return proc;
}

// normal typesetting 

void wsclean(char* txt){
    int nl = 0; // count of newlines
    size_t i;
    for (i = strlen(txt); i > 0; i--) { // start at end [i-1] and dec
        if (txt[i-1] == '\n') nl++; // count up newlines
        else if (txt[i-1] != ' ') break; // and break on unpadded text
    }
    memset(txt+i, '\n', nl); // add #nl newlines at [i, i+nl)
    txt[i+nl] = 0; // finish string
}
#define nbspchr (char) 255
static void nbspclean(char* txt){
    for (; *txt != 0; txt++){
        if (*txt == nbspchr) *txt = ' ';
    }
}

char* wordset(char* txt){
    char* orig = txt; // txt will be manipulated
    int ws = 0; // zero means do not cut
    for (int i=0; txt[i] != 0; i++){ // turn into a nested loop
        if (txt[i] == ' ' || txt[i] == '\n') ws = i;
        // nl's (multiline input) and spaces are proper linebreaks
        if (txt[i] == '\n' || (ws && i >= width && ws != i) ){
            txt += ws;
            txt[0] = '\n';
            ws = 0;
            i = 0;
        }
    }

    wsclean(orig); // remove trailing whitespace
    nbspclean(orig);

    return orig;
}


static char* norm(void){
    return popstrbuf(inbuf, chrfill('\n'));
}

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

static void nbspsub(char* txt){
    for (; (*txt) != 0; txt++){
        if (*txt == nbsp) *txt = nbspchr;
    }
}

char* line(void){
    size_t sz;
    if ( (sz = fillbuf(2)) == 0)
        return "";
    char twobytes[3];
    char* peek = peekstrbuf(inbuf, 0, 2); // .., .\n, or ^.?
    memcpy(twobytes, peek, 3); free(peek);
    if (sz == 1 || twobytes[1] == '\n') return norm();
    if (twobytes[0] == '.') popchrbuf(inbuf);
    char* out;
    if (twobytes[0] == '.' && twobytes[1] != '.'){
        char* data = cmd();
        if (data) return data;
        out = line();
    } else {
        out = norm();
    }
    nbspsub(out);
    return out;
}

// orchestration

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