/*++
Copyright (c) 2011 Microsoft Corporation

Module Name:

    zstring.h

Abstract:

    String wrapper for unicode/ascii internal strings as vectors

Author:

    Nikolaj Bjorner (nbjorner) 2021-01-26

--*/
#pragma once

#include <cstdint>
#include <string>
#include "util/buffer.h"
#include "util/rational.h"
#include "util/vector.h"

enum class string_encoding {
  ascii, // exactly 8 bits
  unicode,
  bmp // basic multilingual plane; exactly 16 bits
};

class zstring {
private:
    buffer<uint32_t> m_buffer;
    bool well_formed() const;
    bool is_escape_char(char const *& s, unsigned& result);
public:
    static unsigned unicode_max_char() { return 196607; }
    static unsigned unicode_num_bits() { return 18; }
    static unsigned bmp_max_char() { return 65535; }
    static unsigned bmp_num_bits() { return 16; }
    static unsigned ascii_max_char() { return 255; }
    static unsigned ascii_num_bits() { return 8; }
    static unsigned max_char() {
      switch (get_encoding()) {
      case string_encoding::unicode:
          return unicode_max_char();
      case string_encoding::bmp:
          return bmp_max_char();
      case string_encoding::ascii:
          return ascii_max_char();
      }
      return unicode_max_char();
    }
    static unsigned num_bits() {
      switch (get_encoding()) {
      case string_encoding::unicode:
          return unicode_num_bits();
      case string_encoding::bmp:
          return bmp_num_bits();
      case string_encoding::ascii:
          return ascii_num_bits();
      }
      return unicode_num_bits();
    }
    static string_encoding get_encoding();
    zstring() = default;
    zstring(char const* s);
    zstring(const std::string &str) : zstring(str.c_str()) {}
    zstring(rational const& r): zstring(r.to_string()) {}
    zstring(unsigned sz, unsigned const* s) { m_buffer.append(sz, s); SASSERT(well_formed()); }
    zstring(unsigned ch);
    zstring replace(zstring const& src, zstring const& dst) const;
    zstring reverse() const;
    std::string encode() const;
    unsigned length() const { return m_buffer.size(); }
    unsigned operator[](unsigned i) const { return m_buffer[i]; }
    bool empty() const { return m_buffer.empty(); }
    bool suffixof(zstring const& other) const;
    bool prefixof(zstring const& other) const;
    bool contains(zstring const& other) const;
    int  indexofu(zstring const& other, unsigned offset) const;
    int  last_indexof(zstring const& other) const;
    zstring extract(unsigned offset, unsigned length) const;
    zstring operator+(zstring const& other) const;
    bool operator==(const zstring& other) const;
    bool operator!=(const zstring& other) const;
    unsigned hash() const;

    void reset() { m_buffer.reset(); }
    zstring& operator+=(zstring const& other) { m_buffer.append(other.m_buffer); return *this; }
    uint32_t const* begin() const { return m_buffer.begin(); }
    uint32_t const* end() const { return m_buffer.end(); }

    friend std::ostream& operator<<(std::ostream &os, const zstring &str);
    friend bool operator<(const zstring& lhs, const zstring& rhs);
};

// half-open character interval [lo, hi)
struct char_range {
    unsigned m_lo;
    unsigned m_hi; // exclusive

    char_range(): m_lo(0), m_hi(0) {}
    char_range(unsigned c): m_lo(c), m_hi(c + 1) {}
    char_range(unsigned lo, unsigned hi): m_lo(lo), m_hi(hi) { SASSERT(lo <= hi); }

    bool is_empty() const { return m_lo == m_hi; }
    bool is_unit()  const { return m_hi == m_lo + 1; }
    unsigned length() const { return m_hi - m_lo; }
    bool contains(unsigned c) const { return c >= m_lo && c < m_hi; }

    bool operator==(char_range const& o) const { return m_lo == o.m_lo && m_hi == o.m_hi; }
    bool operator<(char_range const& o) const {
        return m_lo < o.m_lo || (m_lo == o.m_lo && m_hi < o.m_hi);
    }
};

// sorted list of non-overlapping character intervals
class char_set {
    svector<char_range> m_ranges;
public:
    char_set() = default;
    explicit char_set(char_range const& r) { if (!r.is_empty()) m_ranges.push_back(r); }

    static char_set full(unsigned max_char) { return char_set(char_range(0, max_char + 1)); }

    bool is_empty() const { return m_ranges.empty(); }
    bool is_full(unsigned max_char) const {
        return m_ranges.size() == 1 && m_ranges[0].m_lo == 0 && m_ranges[0].m_hi == max_char + 1;
    }
    bool is_unit() const { return m_ranges.size() == 1 && m_ranges[0].is_unit(); }
    unsigned first_char() const { SASSERT(!is_empty()); return m_ranges[0].m_lo; }

    svector<char_range> const& ranges() const { return m_ranges; }

    // total number of characters in the set
    unsigned char_count() const;

    // membership test via binary search
    bool contains(unsigned c) const;

    // add a single character
    void add(unsigned c);

    // union with another char_set
    void add(char_set const& other);

    // intersect with another char_set, returns the result
    char_set intersect_with(char_set const& other) const;

    // complement relative to [0, max_char]
    char_set complement(unsigned max_char) const;

    // check if two sets are disjoint
    bool is_disjoint(char_set const& other) const;

    // check if this set is a subset of other (every char in this is also in other)
    bool is_subset(char_set const& other) const;

    bool operator==(char_set const& other) const { return m_ranges == other.m_ranges; }

    char_set clone() const { char_set r; r.m_ranges = m_ranges; return r; }

    std::ostream& display(std::ostream& out) const;
};