#ifndef TERRACE_DOCUMENT_H
#define TERRACE_DOCUMENT_H

#include "parser.h"
#include <string.h>
#include <stddef.h>

// String view structure for safe, zero-allocation string handling
typedef struct {
  const char* str;
  size_t len;
} terrace_string_view_t;

// Convenience macros for common patterns
#define TERRACE_STRING_VIEW_NULL ((terrace_string_view_t){.str = NULL, .len = 0})
#define TERRACE_STRING_VIEW_FROM_CSTR(cstr) ((terrace_string_view_t){.str = cstr, .len = strlen(cstr)})
#define TERRACE_STRING_VIEW_EQUALS_CSTR(view, cstr) \
  ((view).len == strlen(cstr) && strncmp((view).str, cstr, (view).len) == 0)
#define TERRACE_STRING_VIEW_IS_EMPTY(view) ((view).len == 0)

// Safe string view comparison
static inline int terrace_string_view_equals(terrace_string_view_t a, terrace_string_view_t b) {
  return a.len == b.len && (a.len == 0 || strncmp(a.str, b.str, a.len) == 0);
}

// Enhanced node structure for easier navigation
typedef struct terrace_node_s {
  // Line content and metadata
  const char* _raw_line;
  terrace_linedata_t _line_data;
  unsigned int line_number;

  // Parent document reference
  struct terrace_document_s* document;
} terrace_node_t;

// Tracks state of a document being parsed.
typedef struct terrace_document_s {
  // == Internal State == //
  unsigned int _repeat_current_node;
  terrace_node_t _current_node;
  terrace_node_t _pushed_back_node;
  unsigned int _has_pushed_back_node;
  unsigned int _line_number;

  // Legacy fields for backward compatibility
  char* _currentLine;
  terrace_linedata_t lineData;

  // == External Information == //
  // Custom data passed to the readline function
  void* userData;
  /**
   * Line reader function, provided by the user
   * @param {char**} line First argument is a pointer to line buffer
   * @param {void*} userData Second argument is `userData`
   * @returns {int} The number of characters read, or -1 if no characters were read.
   */
  int (*reader)(char** line, void* userData);
} terrace_document_t;

/**
 * Initialize a Terrace document with indent parameters and the function needed to read lines.
 * @param {char} indent The indent character to use. Generally a single space character.
 * @param {int (*reader)(char** line, void* userData)} A function pointer to a function that reads lines sequentially
 * @param {void*} userData A user-supplied pointer to any state information needed by their reader function.
 * @returns {terrace_document_t} An initialized document that can now be used for further parsing.
 */
terrace_document_t terrace_create_document(const char indent, int (*reader)(char** line, void* userData), void* userData) {
  terrace_document_t document = {
    ._repeat_current_node = 0,
    ._current_node = {0},
    ._pushed_back_node = {0},
    ._has_pushed_back_node = 0,
    ._line_number = 0,
    ._currentLine = NULL,
    .lineData = terrace_create_linedata(indent),
    .reader = reader,
    .userData = userData
  };

  return document;
}

// === NEW NODE-BASED API ===

/**
 * Get a string view of the node's head (first word)
 * @param {terrace_node_t*} node Pointer to the node
 * @returns {terrace_string_view_t} String view of the head portion
 */
terrace_string_view_t terrace_node_head(terrace_node_t* node) {
  terrace_string_view_t view = {
    .str = node->_raw_line + node->_line_data.offsetHead,
    .len = node->_line_data.offsetTail - node->_line_data.offsetHead
  };
  return view;
}

/**
 * Get a string view of the node's tail (everything after first word)
 * @param {terrace_node_t*} node Pointer to the node
 * @returns {terrace_string_view_t} String view of the tail portion
 */
terrace_string_view_t terrace_node_tail(terrace_node_t* node) {
  if (node->_line_data.offsetTail >= strlen(node->_raw_line) ||
      node->_raw_line[node->_line_data.offsetTail] != ' ') {
    return TERRACE_STRING_VIEW_NULL;
  }

  const char* tail_start = node->_raw_line + node->_line_data.offsetTail + 1;
  terrace_string_view_t view = {
    .str = tail_start,
    .len = strlen(tail_start)
  };
  return view;
}

/**
 * Get a string view of the node's content (line without indentation)
 * @param {terrace_node_t*} node Pointer to the node
 * @returns {terrace_string_view_t} String view of the content
 */
terrace_string_view_t terrace_node_content(terrace_node_t* node) {
  const char* content_start = node->_raw_line + node->_line_data.offsetHead;
  terrace_string_view_t view = {
    .str = content_start,
    .len = strlen(content_start)
  };
  return view;
}

/**
 * Get a string view of the node's raw content with custom offset
 * @param {terrace_node_t*} node Pointer to the node
 * @param {int} offset Offset from start of line (0 = include all indentation)
 * @returns {terrace_string_view_t} String view from the specified offset
 */
terrace_string_view_t terrace_node_raw(terrace_node_t* node, int offset) {
  if (offset < 0) offset = node->_line_data.offsetHead; // Default to content

  const char* start = node->_raw_line + offset;
  terrace_string_view_t view = {
    .str = start,
    .len = strlen(start)
  };
  return view;
}

/**
 * Get the indentation level of a node
 * @param {terrace_node_t*} node Pointer to the node
 * @returns {unsigned int} Indentation level
 */
unsigned int terrace_node_level(terrace_node_t* node) {
  return node->_line_data.level;
}

/**
 * Get the line number of a node
 * @param {terrace_node_t*} node Pointer to the node
 * @returns {unsigned int} Line number
 */
unsigned int terrace_node_line_number(terrace_node_t* node) {
  return node->line_number;
}

/**
 * Check if the node's head matches a given string
 * @param {terrace_node_t*} node Pointer to the node
 * @param {const char*} match_str String to match against
 * @returns {int} 1 if matches, 0 if not
 */
int terrace_node_is(terrace_node_t* node, const char* match_str) {
  terrace_string_view_t head = terrace_node_head(node);
  return TERRACE_STRING_VIEW_EQUALS_CSTR(head, match_str);
}

/**
 * Check if the node is empty (blank line)
 * @param {terrace_node_t*} node Pointer to the node
 * @returns {int} 1 if empty, 0 if not
 */
int terrace_node_is_empty(terrace_node_t* node) {
  terrace_string_view_t content = terrace_node_content(node);
  for (size_t i = 0; i < content.len; i++) {
    if (content.str[i] != ' ' && content.str[i] != '\t') {
      return 0;
    }
  }
  return 1;
}

// === ENHANCED DOCUMENT ITERATION ===

/**
 * Get the next node from the document
 * @param {terrace_document_t*} doc Pointer to the document
 * @param {terrace_node_t*} node Pointer to store the next node
 * @returns {int} 1 if node was retrieved, 0 if end of document
 */
int terrace_next_node(terrace_document_t* doc, terrace_node_t* node) {
  // Check for pushed back node first
  if (doc->_has_pushed_back_node) {
    *node = doc->_pushed_back_node;
    doc->_has_pushed_back_node = 0;
    return 1;
  }

  // Read next line
  int chars_read = doc->reader(&doc->_currentLine, doc->userData);
  if (chars_read == -1) return 0;

  // Parse the line
  terrace_parse_line(doc->_currentLine, &doc->lineData);

  // Populate node
  node->_raw_line = doc->_currentLine;
  node->_line_data = doc->lineData;
  node->line_number = doc->_line_number++;
  node->document = doc;

  return 1;
}

/**
 * Push back a node to be returned by the next call to terrace_next_node
 * @param {terrace_document_t*} doc Pointer to the document
 * @param {terrace_node_t*} node Pointer to the node to push back
 */
void terrace_push_back_node(terrace_document_t* doc, terrace_node_t* node) {
  doc->_pushed_back_node = *node;
  doc->_has_pushed_back_node = 1;
}

// === ENHANCED MACROS FOR ITERATION ===

/**
 * Iterate through all nodes in a document
 * Usage: TERRACE_FOR_EACH_NODE(doc, node) { ... }
 */
#define TERRACE_FOR_EACH_NODE(doc, node) \
  terrace_node_t node; \
  while (terrace_next_node(doc, &node))

/**
 * Iterate through child nodes of a given parent level (supports arbitrary nesting)
 * Usage: TERRACE_FOR_CHILD_NODES(doc, parent_level, node) { ... }
 */
#define TERRACE_FOR_CHILD_NODES(doc, parent_level, node) \
  terrace_node_t node; \
  while (terrace_next_node(doc, &node) && terrace_node_level(&node) > parent_level)

/**
 * Check if a node matches a string (shorthand for terrace_node_is)
 */
#define TERRACE_NODE_MATCHES(node, str) terrace_node_is(&node, str)

// === LEGACY API FOR BACKWARD COMPATIBILITY ===

/**
 * Returns the number of indent characters of the current line
 * @param {terrace_document_t*} doc A pointer to the Terrace document being parsed
 * @returns {unsigned int} The indent level of the current line
 */
unsigned int terrace_level(terrace_document_t* doc) {
  return doc->lineData.level;
}

/**
 * Get a string with the current line contents (legacy API)
 * @param {terrace_document_t*} doc A pointer to the Terrace document being parsed
 * @param {int} startOffset How many indent characters to skip before outputting the line contents.
 * @returns {char*} The line contents starting from `startOffset`
 */
char* terrace_line(terrace_document_t* doc, int startOffset) {
  if (startOffset == -1) startOffset = doc->lineData.level;
  return doc->_currentLine + startOffset;
}

// === NEW STRING VIEW API ===

/**
 * Get string view of current line head (legacy compatibility)
 * @param {terrace_document_t*} doc Pointer to document
 * @returns {terrace_string_view_t} String view of head
 */
terrace_string_view_t terrace_head_view(terrace_document_t* doc) {
  terrace_string_view_t view = {
    .str = doc->_currentLine + doc->lineData.offsetHead,
    .len = doc->lineData.offsetTail - doc->lineData.offsetHead
  };
  return view;
}

/**
 * Get string view of current line tail (legacy compatibility)
 * @param {terrace_document_t*} doc Pointer to document
 * @returns {terrace_string_view_t} String view of tail
 */
terrace_string_view_t terrace_tail_view(terrace_document_t* doc) {
  if (doc->lineData.offsetTail >= strlen(doc->_currentLine) ||
      doc->_currentLine[doc->lineData.offsetTail] != ' ') {
    return TERRACE_STRING_VIEW_NULL;
  }

  const char* tail_start = doc->_currentLine + doc->lineData.offsetTail + 1;
  terrace_string_view_t view = {
    .str = tail_start,
    .len = strlen(tail_start)
  };
  return view;
}

/**
 * Get string view of current line content (legacy compatibility)
 * @param {terrace_document_t*} doc Pointer to document
 * @param {int} offset Offset from start of line
 * @returns {terrace_string_view_t} String view from offset
 */
terrace_string_view_t terrace_line_view(terrace_document_t* doc, int offset) {
  if (offset == -1) offset = doc->lineData.level;

  const char* start = doc->_currentLine + offset;
  terrace_string_view_t view = {
    .str = start,
    .len = strlen(start)
  };
  return view;
}

/**
 * Enhanced match function using string views
 * @param {terrace_document_t*} doc Pointer to document
 * @param {const char*} match_str String to match
 * @returns {int} 1 if matches, 0 if not
 */
int terrace_match_view(terrace_document_t* doc, const char* match_str) {
  terrace_string_view_t head = terrace_head_view(doc);
  return TERRACE_STRING_VIEW_EQUALS_CSTR(head, match_str);
}

// Enhanced legacy macro
#define TERRACE_MATCH(doc, str) terrace_match_view(doc, str)

/**
 * Get the *length* of the first "word" of a line (legacy API)
 * @param {terrace_document_t*} doc A pointer to the current document state struct.
 * @returns {int} The length of the `head` portion (first word) of a line
 */
unsigned int terrace_head_length(terrace_document_t* doc) {
  return doc->lineData.offsetTail - doc->lineData.offsetHead;
}

/**
 * Get a char pointer to everything following the first "word" of a line (legacy API)
 * @param {terrace_document_t*} doc A pointer to the current document state struct.
 * @returns {char*} The remainder of the line following the `head` portion, with no leading space.
 */
char* terrace_tail(terrace_document_t* doc) {
  return doc->_currentLine + doc->lineData.offsetTail + 1;
}

/**
 * Quickly check if the current line head matches a specified value (legacy API)
 * @param {terrace_document_t*} doc A pointer to the current document state struct.
 * @param {const char*} matchHead A string to check against the line `head` for equality.
 * @returns {char} A byte set to 0 if the head does not match, or 1 if it does match.
 */
char terrace_match(terrace_document_t* doc, const char* matchHead) {
  return terrace_match_view(doc, matchHead);
}

/**
 * Advances the current position in the terrace document (legacy API)
 * @param {terrace_document_t*} doc A pointer to the current document state struct.
 * @param {int} levelScope If set above -1, will return `0` when it encounters a line at or below `levelScope`
 * @returns {char} Returns `1` after parsing a line, or `0` if the document has ended
 */
char terrace_next(terrace_document_t* doc, int levelScope) {
  // Legacy implementation using new node-based system
  terrace_node_t node;
  if (!terrace_next_node(doc, &node)) return 0;

  // Update legacy fields for backward compatibility
  doc->lineData = node._line_data;
  doc->_currentLine = (char*)node._raw_line;

  // Check level scope
  if (levelScope != -1 && (int)terrace_node_level(&node) <= levelScope) {
    terrace_push_back_node(doc, &node);
    return 0;
  }

  return 1;
}

#endif