#include "editor/decl.h"
#include "io/knot.h"
#include "io/sysio.h"
#include "utils/utils.h"

struct GraphemeIterator {
  char *line{nullptr};
  uint32_t len{0};

  GraphemeIterator(char *line, uint32_t len) : line(line), len(len) {}

  char *next(uint32_t *o_len, uint32_t *o_width) {
    if (!line || len == 0)
      return nullptr;
    char *cur = line;
    uint32_t g = grapheme_next_character_break_utf8(cur, len);
    if (o_width)
      *o_width = display_width(cur, g);
    if (o_len)
      *o_len = g;
    line += g;
    len -= g;
    return cur;
  }
};

struct VisualIterator {
  LineIterator *it{nullptr};
  uint32_t line_index{UINT32_MAX};
  uint32_t offset{0};
  uint32_t len{0};
  bool first{true};
  char *line{nullptr};
  uint32_t render_width{io::cols};
  std::stack<std::pair<Coord, Coord>> prev_stack;

  VisualIterator(Knot *root, Coord pos, uint32_t width)
      : it(begin_l_iter(root, pos.row)), line_index(pos.row - 1),
        offset(pos.col), render_width(width) {}

  std::pair<Coord, Coord> prev() {
    if (!it)
      return {{UINT32_MAX, UINT32_MAX}, {UINT32_MAX, UINT32_MAX}};
    if (prev_stack.empty())
      return _prev();
    auto ret = prev_stack.top();
    offset = ret.first.col;
    prev_stack.pop();
    return ret;
  }

  std::pair<Coord, Coord> _prev() {
    if (!it)
      return {{UINT32_MAX, UINT32_MAX}, {UINT32_MAX, UINT32_MAX}};
    line_index--;
    line = prev_line(it, &len);
    if (!line)
      return {{UINT32_MAX, UINT32_MAX}, {UINT32_MAX, UINT32_MAX}};
    if (len > 0 && line[len - 1] == '\n')
      len--;
    offset = first ? offset : 0;
    first = false;
    GraphemeIterator g(line + offset, len - offset);
    uint32_t o_len, o_width, rendered = 0, advance = 0;
    while (g.next(&o_len, &o_width)) {
      if (rendered + o_width > render_width) {
        prev_stack.push({{line_index, offset}, {line_index, offset + advance}});
        offset += advance;
        rendered = 0;
        advance = 0;
      }
      advance += o_len;
      rendered += o_width;
    }
    return {{line_index, offset}, {line_index, offset + advance}};
  }

  std::pair<Coord, Coord> next() {
    if (!it)
      return {{UINT32_MAX, UINT32_MAX}, {UINT32_MAX, UINT32_MAX}};
    if (!line) {
      line_index++;
      line = next_line(it, &len);
      if (!line)
        return {{UINT32_MAX, UINT32_MAX}, {UINT32_MAX, UINT32_MAX}};
      if (len > 0 && line[len - 1] == '\n')
        len--;
      offset = first ? offset : 0;
      first = false;
    }
    GraphemeIterator g(line + offset, len - offset);
    uint32_t o_len, o_width, rendered = 0, advance = 0;
    while (g.next(&o_len, &o_width)) {
      if (rendered + o_width > render_width) {
        offset += advance;
        return {{line_index, offset - advance}, {line_index, offset}};
      }
      advance += o_len;
      rendered += o_width;
    }
    offset += advance;
    if (offset >= len)
      line = nullptr;
    return {{line_index, offset}, {line_index, offset + advance}};
  }

  ~VisualIterator() {
    if (!it)
      return;
    free(it->buffer);
    free(it);
  }
};