// pattern_util_box.hako — Shared utilities for MirBuilder lowers

using selfhost.shared.json.utils.json_frag as JsonFragBox
using selfhost.shared.common.string_helpers as StringHelpers

static box PatternUtilBox {
  map_cmp(sym) { if sym=="<" {return "Lt"} if sym==">" {return "Gt"} if sym=="<=" {return "Le"} if sym==">=" {return "Ge"} if sym=="==" {return "Eq"} if sym=="!=" {return "Ne"} return null }
  // Normalize (op, swapped, limit) → (cmp, limit') where cmp in {Lt, Le, Gt, Ge}
  // swapped=0: i ? L, swapped=1: L ? i
  normalize_cmp_limit(op, swapped, limit_str) {
    local op1 = "" + op
    local ls = "" + limit_str
    if swapped == 0 {
      if op1 == "<" { return "Lt:" + ls }
      if op1 == "<=" { return "Lt:" + StringHelpers.int_to_str(JsonFragBox._str_to_int(ls) + 1) }
      if op1 == ">" { return "Gt:" + ls }
      if op1 == ">=" { return "Ge:" + ls }
      if op1 == "!=" { return "Lt:" + ls } // count(init=0,step=1) 前提の近似
      return null
    } else {
      if op1 == ">" { return "Lt:" + ls }
      if op1 == ">=" { return "Lt:" + StringHelpers.int_to_str(JsonFragBox._str_to_int(ls) + 1) }
      if op1 == "<" { return "Gt:" + ls }
      if op1 == "<=" { return "Ge:" + ls }
      if op1 == "!=" { return "Lt:" + ls } // 安全近似（入替側）
      return null
    }
  }
  // Normalize limit for canonical (i < limit) form.
  // When swapped==0, expects op in {'<','<='}; when swapped==1 (Int on lhs, Var on rhs), expects op in {'>','>='}.
  // Returns adjusted limit string or null if unsupported.
  normalize_limit_for_lt(op, swapped, limit_str) {
    local op1 = "" + op
    local ls = "" + limit_str
    if swapped == 0 {
      if op1 == "<" { return ls }
      if op1 == "<=" { return StringHelpers.int_to_str(JsonFragBox._str_to_int(ls) + 1) }
      if op1 == "!=" { return ls } // safe for count(init=0,step=1)
      return null
    } else {
      if op1 == ">" { return ls }
      if op1 == ">=" { return StringHelpers.int_to_str(JsonFragBox._str_to_int(ls) + 1) }
      return null
    }
  }
  find_local_int_before(s, name, before_pos) {
    local pos=0; local last=-1
    loop(true){ local k=JsonFragBox.index_of_from(s, "\"type\":\"Local\"",pos); if k<0||k>=before_pos{break}; local kn=JsonFragBox.index_of_from(s, "\"name\":\"",k); if kn>=0{ local ii=kn+8; local nn=s.length(); local jj=ii; loop(jj<nn){ if s.substring(jj,jj+1)=="\"" {break} jj=jj+1 } if s.substring(ii,jj)==name { last=k } } pos=k+1 }
    if last<0 { return null }
    // Bound the search between this Local and the next Local/before_pos
    local next = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last + 1)
    if next < 0 || next > before_pos { next = before_pos }
    local ki = s.indexOf("\"type\":\"Int\"", last)
    if ki < 0 || ki >= next { return null }
    local kv = s.indexOf("\"value\":", ki)
    if kv < 0 || kv >= next { return null }
    return JsonFragBox.read_int_after(s, kv+8)
  }
  find_local_bool_before(s, name, before_pos) {
    local pos=0; local last=-1
    loop(true){ local k=JsonFragBox.index_of_from(s, "\"type\":\"Local\"",pos); if k<0||k>=before_pos{break}; local kn=JsonFragBox.index_of_from(s, "\"name\":\"",k); if kn>=0{ local ii=kn+8; local nn=s.length(); local jj=ii; loop(jj<nn){ if s.substring(jj,jj+1)=="\"" {break} jj=jj+1 } if s.substring(ii,jj)==name { last=k } } pos=k+1 }
    if last<0 { return null }
    local next = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last + 1)
    if next < 0 || next > before_pos { next = before_pos }
    local kb = s.indexOf("\"type\":\"Bool\"", last)
    if kb < 0 || kb >= next { return null }
    local kv = s.indexOf("\"value\":", kb)
    if kv < 0 || kv >= next { return null }
    // JSON v0 uses 0/1 for bool values, not true/false literals
    return JsonFragBox.read_int_after(s, kv+8)
  }

  // Find the last Local(Int) before a given position (name-agnostic).
  // Returns string digits or null when not found.
  find_any_local_int_before(s, before_pos) {
    local pos = 0; local last_k = -1; local n = ("" + s).length()
    loop(true) {
      local k = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", pos)
      if k < 0 || k >= before_pos { break }
      last_k = k
      pos = k + 1
    }
    if last_k < 0 { return null }
    // Limit search to the next Local or before_pos
    local next = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last_k + 1)
    if next < 0 || next > before_pos { next = before_pos }
    // Constrain to Local.expr → Int
    local ti = ("" + s).indexOf("\"expr\":{\"type\":\"Int\"", last_k)
    if ti < 0 || ti >= next { return null }
    local kv = ("" + s).indexOf("\"value\":", ti)
    if kv < 0 || kv >= next { return null }
    return JsonFragBox.read_int_after(s, kv + 8)
  }

  // Find the last Local(String) before a given position (name-agnostic).
  // Returns raw string (unquoted) or null when not found.
  find_any_local_string_before(s, before_pos) {
    local pos = 0; local last_k = -1
    loop(true) {
      local k = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", pos)
      if k < 0 || k >= before_pos { break }
      last_k = k
      pos = k + 1
    }
    if last_k < 0 { return null }
    local next = JsonFragBox.index_of_from(s, "\"type\":\"Local\"", last_k + 1)
    if next < 0 || next > before_pos { next = before_pos }
    // Constrain to Local.expr → String
    local ts = ("" + s).indexOf("\"expr\":{\"type\":\"String\"", last_k)
    if ts < 0 || ts >= next { return null }
    local kv = ("" + s).indexOf("\"value\":", ts)
    if kv < 0 || kv >= next { return null }
    return JsonFragBox.read_string_after(s, kv + 8)
  }
}