#ifndef TERRACE_PARSER_H
#define TERRACE_PARSER_H

// Holds the parsed information from each line.
typedef struct terrace_linedata_s {
  // Which character is being used for indentation. Avoids having to specify it on each terrace_parse_line call.
  char indent;
  // How many indent characters are present in the current line before the first non-indent character.
  unsigned int level;
  // The number of characters before the start of the line's "head" section.
  // (Normally the same as `level`)
  unsigned int offsetHead;
  // The number of characters before the start of the line's "tail" section.
  unsigned int offsetTail;
} terrace_linedata_t;

terrace_linedata_t terrace_create_line_data(const char indent) {
  terrace_linedata_t line_data = { .indent = indent, .level = 0, .offsetHead = 0, .offsetTail = 0 };
  return line_data;
}

/**
 * Core Terrace parser function, sets level, offsetHead, and offsetTail in a lineData struct based on the current line.
 * @param char* line A pointer to the line to parse as a C-style string. Shouldn't end with a newline.
 * @param terrace_linedata_t* lineData A pointer to the terrace_linedata_t struct to store information about the current line in.
 */
void terrace_parse_line(const char *line, terrace_linedata_t *lineData) {
  // Empty lines are nullptr/0 as they have no characters. (The newline character should be stripped off.)
  // Special case handling for these allows them to be parsed extra quickly.
  if (!line) {
    // Empty lines are treated as having the same level as the previous line, so lineData->line is not updated.
    lineData->offsetHead = 0;
    lineData->offsetTail = 0;
  } else {
    // Count the number of indent characters in the current line.
    unsigned int level = 0;
    while (line[level] == lineData->indent) ++level;
    lineData->level = level;

    // Set offsetHead and offsetTail to level to start with.
    // offsetHead should always be equal to level, and offsetTail will always be equal to or greater than level.
    lineData->offsetHead = level;
    lineData->offsetTail = level;

    // Increment offsetTail until we encounter a space character (start of tail) or reach EOL (no tail present).
    while (line[lineData->offsetTail] && line[lineData->offsetTail] != ' ') ++lineData->offsetTail;
  }
}

#endif