#include "types.h"

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

static char next_char(FILE* file) {
    char c;
    if (fread(&c, 1, 1, file) != 1) {
        return EOF;
    } else {
        return c;
    }
}

static Symbol next_symbol(FILE* file) {
    char c = next_char(file); 
retest:
    switch (c) {
        case '<':
            return MoveLeft;
        case '>':
            return MoveRight;
        case '+':
            return Increment;
        case '-':
            return Decrement;
        case '[':
            return StartLoop;
        case ']':
            return EndLoop;
        case '.':
            return PutChar;
        case ',':
            return GetChar;
        case '*':
            return Allocate;
        case '!':
            return Free;
        case '(':
            return EnterTape;
        case ')':
            return LeaveTape;
        case '`':
            return PutString;
        case '~':
            return GetString;
        case '%':
            return Clear;
        case '\n':
        case '\t':
        case ' ':
            while(c = next_char(file), c == '\n' || c == '\t' || c == ' ');
            goto retest;
        case '/':
            while(c = next_char(file), c != '\n' && c != EOF);
            goto retest;
        case EOF:
            return Eof;
        default:
            c = next_char(file);
            goto retest;
    }
}

void program_init(Program* program, FILE* file) {
    uint32_t capacity = 8;

    program->data = malloc(capacity * sizeof(struct instruction));
    program->len = 0;
    program->index = 0;

    Stack stack;
    stack_init(&stack, 8);

    Symbol s;
    while(true) {
        s = next_symbol(file);
        
        if (program->len == capacity) {
            capacity *= 2;
            program->data = realloc(program->data, capacity * sizeof(struct instruction));
        }

        program->data[program->len].s = s;
        program->data[program->len].j = 0;

        if (s == StartLoop) {
            stack_pushi(&stack, program->len);
        } else if (s == EndLoop) {
            uint32_t i = stack_popi(&stack);
            program->data[program->len].j = i;
            if (i != 0 || program->data[i].j == 0) {
                program->data[i].j = program->len;
            }
        }

        program->len++;

        if (s == Eof) break;
    }
    stack_free(&stack);
    fclose(file);
}

void program_get(Program* program, Symbol* symbol) {
    if (program->index >= program->len) {
        *symbol = Eof;
        return;
    }
    *symbol = program->data[program->index].s;
}

uint32_t program_get_jump(Program* program) {
    if (program->index >= program->len) {
        return 0;
    }
    return program->data[program->index].j;
}

void program_next(Program* program) {
    program->index++;
}

void program_seek(Program* program, uint32_t index) {
    program->index = index;
}

void program_free(Program* program) {
    free(program->data);
}