#include "source.h"
#include "util.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

struct source {
  char* contents;
  const char* file_name;
  size_t size;
};

static source_t *_source_alloc(struct source data) {
  source_t *source = malloc(sizeof (struct source));
  if (source == NULL) {
    die("Out of memory: cannot allocate source struct");
  }
  *source = data;
  return source;
}

static struct source _read_file(const char *file_name) {
    FILE *f = fopen(file_name, "r");
    if (!f) {
      die("Cannot read file %s", file_name);
    }
    size_t capacity = 1024;  // initial buffer size
    size_t length = 0;
    char *buffer = malloc(capacity);
    if (buffer == NULL) {
        die("Out of memory: cannot allocate buffer for %s", file_name);
    }
    int ch;
    while ((ch = fgetc(f)) != EOF) {
        if (length + 1 >= capacity) {
            capacity *= 2;
            char *tmp = realloc(buffer, capacity);
            if (tmp == NULL) {              
                fclose(f);
                die("Out of memory: cannot enlarge buffer for %s", file_name);
            }
            buffer = tmp;
        }
        buffer[length++] = (char)ch;
    }

    buffer[length] = '\0'; // null-terminate
    fclose(f);
    struct source it;
    it.contents = buffer;
    it.size = length;
    it.file_name = file_name;
    return it;
}

source_t *source_alloc_from_file(char* file_name) {
  return _source_alloc(_read_file(file_name));
}

source_t *source_alloc(const char* file_name,  char* contents) {
  struct source it = { .file_name = file_name, .contents = contents, .size = strlen(contents)};
  return _source_alloc(it); 
}

pos_t source_next_pos(source_t *source, pos_t pos) {
  if (source->contents[pos.idx] == '\n') {
    pos.idx++;
    pos.col = 0;
    pos.line++;
  } else {
    pos.idx++;
    pos.col++;
  }
  return pos;
}

void source_print_pos(source_t *source, pos_t pos) {
  fprintf(stderr,"%s:%d:%d", source->file_name,pos.line + 1,pos.col + 1);
}

void source_print_line(source_t *source, pos_t pos, int highlight_len) {
  fprintf(stderr,"%5d | ",pos.line+1);
  for (size_t i = pos.idx - pos.col; 
    i < source->size && source->contents[i] != '\n' && source->contents[i] != '\0'; 
    i++)  fputc(source->contents[i],stderr);
  if (highlight_len <= 0) return;
  fprintf(stderr,"\n      | ");
  for (int i = 0; i < pos.col; i++) fputc(' ',stderr);
  for (int i = 0; i < highlight_len; i++) fputc('^',stderr);
}

const char* source_contents_from(source_t* source, pos_t pos) {
  if (pos.idx >= source->size) {
    return source->contents + source->size;
  } else {
    return source->contents + pos.idx;
  }
}

void source_dealloc(source_t* source) {
  free(source->contents);
}