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

// Location in the source file
typedef struct Location {
  // Offset in file of the first character
  i32 line;
  // Offset on the line of the first character
  u16 column;
  // Length in bytes
  u16 size;
} Location_t;

typedef struct Token {
  // identifying tag
  enum TokenType {
    t_error,
    t_size,
    t_multiply,
    t_divide,
    t_add,
    t_subtract,
    t_whitespace,
    t_newline,
    t_number,
  } type;

  // Offset(s) in the buffer where the token occurs.
  // If type is t_size, then location is an i64 "size" -- only used to store the
  // number of tokens.
  // If type is t_newline, then location is a Location_t line, where `line`
  // holds the offset into the text buffer where the newline is located, column
  // holds the line number,
  // and size holds the length of the line.
  union {
    Location_t location;
    Location_t line;
    i64 size;
  } location;
} Token_t;

// #define Location_to_i64(location) \
//   (i64)(((i64)location.line << 32) | (location.column << 16) | location.size)
// #define i64_to_Location(long_int) \
//   (Location_t) { \
//     .line = (long_int >> 32), .column = (long_int >> 16) & ((1 << 16) - 1), \
//     .size = long_int & ((1 << 16) - 1), \
//   }

// Should also add helper structure with pointers to each line

static isize f_read(FILE* stream, char** dst);
static i64 f_size(FILE* stream);
static void l_print_token(Token_t token, Location_t** lines, char* text);
static Location_t** l_read(char* text, isize text_length, Token_t** dst);

int
main(int argc, char* argv[]) {
  if (argc == 2) {
    FILE* f              = NULL;
    char* contents       = NULL;
    isize content_length = -1;
    Token_t* tokens      = NULL;
    Location_t** lines   = NULL;

    f                    = fopen(argv[1], "r");
    if (f == NULL) {
      fprintf(stdout, "! Failed to open file: %s\n", argv[1]);
    }

    if (f != NULL) {
      content_length = f_read(f, &contents);
      if (content_length > 0) {
        printf("%s:%ld\n%s\n", argv[1], content_length, contents);
      }
      fclose(f);
    }

    if (content_length > 0) {
      lines = l_read(contents, strlen(contents), &tokens);
    }

    if (lines != NULL) {
      i64 num_tokens = tokens[0].location.size;
      printf("%ld tokens\n", num_tokens);
      for (int t = 0; t < num_tokens; t++) {
        l_print_token(tokens[t], lines, contents);
      }
      free(contents);
    }
  }
  return 0;
}

/* Copies the contents of the file stream to *dst.
 * @param  stream An open file stream.
 * @param  dst** Destination buffer. If *dst is NULL allocates a buffer the size
 * of stream using malloc.
 * @return The number of bytes copied into dst.
 * @error  returns -1 on error.
 */
static isize
f_read(FILE* stream, char** dst) {
  i64 file_sz = f_size(stream);

  if (dst == NULL) {
    fprintf(stderr, "! Got NULL ptr\n");
  }

  if (dst != NULL && *dst == NULL && file_sz > 0) {
    *dst = (char*)malloc(file_sz * sizeof(char));
  }

  if (dst != NULL && *dst == NULL && file_sz > 0) {
    fprintf(stderr, "! Failed to allocate %ld bytes\n", file_sz * sizeof(char));
  }

  isize bytes_read = -1;
  if (dst != NULL && *dst != NULL && file_sz > 0) {
    bytes_read = fread(*dst, sizeof(char), file_sz, stream);
  }

  if (bytes_read < file_sz) {
    fprintf(stderr, "! Failed to read file, read %ld out of %ld bytes\n",
            bytes_read, file_sz);
  }

  return bytes_read;
}

/* Returns the size in bytes and rewinds the stream.
 * @param  stream An open file stream.
 * @return the size of the file in bytes.
 * @error  Returns -1 on error.
 */
static i64
f_size(FILE* stream) {
  // Could ftell and rewind to previous position, but scratch that
  i64 size  = -1;
  i32 error = fseek(stream, 0, SEEK_END);

  if (error) {
    // TODO: handle pipes (check errno == ESPIPE)
    fprintf(stderr, "! Failed to seek file: %s\n", strerror(errno));
  } else {
    size = ftell(stream);
    rewind(stream);
  }
  return size;
}

static void
l_print_token(Token_t token, Location_t* lines[], char* text) {
  fprintf(stdout, "[%d,%d:%d]", token.location.location.line + 1,
          token.location.location.column + 1, token.location.location.size);
  switch (token.type) {
  case t_error:
    fputs(" error ", stdout);
    break;
  case t_size:
    fprintf(stdout, "size");
    break;
  case t_multiply:
    fputs(" * ", stdout);
    break;
  case t_divide:
    fputs(" / ", stdout);
    break;
  case t_add:
    fputs(" + ", stdout);
    break;
  case t_subtract:
    fputs(" - ", stdout);
    break;
  case t_number:
    fputs("number:", stdout);
    Location_t* line = lines[token.location.location.line];
    fwrite(&text[line->line + token.location.location.column],
           token.location.location.size, sizeof(char), stdout);
    break;
  case t_newline:
    fprintf(stdout, "\\n offset:%d line:%d length:%d", token.location.line.line,
            token.location.line.column, token.location.line.size);
    break;
  default:
    break;
  }
  puts("");
}

/* Reads text and parses it into an array of tokens
 * @param  text A buffer holding the input text
 * @return a pointer to dst
 * @error  Returns NULL on error.
 */
static Location_t**
l_read(char* text, isize text_length, Token_t** dst) {
  Location_t** lines = NULL;
  if (dst == NULL) {
    fprintf(stderr, "dst is NULL");
  }
  if (text_length > 0 && dst != NULL && *dst == NULL) {
    *dst = (Token_t*)malloc(text_length * sizeof(Token_t));
  }

  if (text_length > 0 && dst != NULL && *dst == NULL) {
    fprintf(stderr, "! Failed to allocate %ld bytes\n",
            text_length * sizeof(Token_t));
  }

  if (text_length > 0 && dst != NULL && *dst != NULL) {
    // Offset in text (used for Location.line
    isize i                       = 0;
    // Column counter
    u16 c                         = 0;
    // Line offset
    i32 l                         = 0;
    // Token counter
    isize t                       = 2;
    i32 error                     = 0;
    enum TokenType token_previous = t_error;
    enum TokenType token          = t_error;

    (*dst)[1].type                = t_newline;
    Location_t* line_current      = &(*dst)[1].location.line;
    line_current->line            = 0;
    line_current->column          = l;
    line_current->size            = 0;

    // TODO: rewrite to
    // if token != last-token
    //   dst = token,line,col
    //   last-token = token
    //   t++;
    // while (last-token != error)
    do {
      switch (text[i]) {
        //    case t_size:
        // break;
      case '*':
        token = t_multiply;
        break;
      case '/':
        token = t_divide;
        break;
      case t_add:
        token = t_add;
        break;
      case '-':
        token = t_subtract;
        break;

      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
        token = t_number;
        break;
      case '+':
        token = t_add;
        break;

      case ' ':
      case '\t':
        token = t_whitespace;
        break;

      case '\n':
        token = t_newline;
        break;

      default:
        token = t_error;
        error = 1;
        break;
      }

      if (token == t_newline) {
        l++;
        line_current->size             = c;
        (*dst)[t].type                 = token;
        (*dst)[t].location.line.line   = i + 1;
        (*dst)[t].location.line.column = l;
        (*dst)[t].location.line.size   = 0;

        line_current                   = &(*dst)[t].location.line;
        c                              = 0;
        t++;
        token_previous = token;
      } else if (token == token_previous) {
        (*dst)[t - 1].location.location.size++;
        c++;
      } else {
        (*dst)[t].type                     = token;
        (*dst)[t].location.location.line   = l;
        (*dst)[t].location.location.column = c;
        (*dst)[t].location.location.size   = 1;
        c++;
        t++;
        token_previous = token;
      }

      i++;
    } while (!error && i < text_length);

    (*dst)[0].type          = t_size;
    (*dst)[0].location.size = t;

    if ((*dst)[t - 1].type != t_newline) {
      l++;
      line_current->size = c;
    }

    lines = (Location_t**)malloc(sizeof(Location_t*) * l);
    i32 j = 0;
    for (int u = 0; u < t; u++) {
      if ((*dst)[u].type == t_newline) {
        lines[j] = &(*dst)[u].location.line;
        j++;
      }
    }
  }

  return lines;
}