// Moved from apps/selfhost-compiler/boxes/parser/expr/parser_expr_box.hako
// ParserExprBox — expression parser coordinator
// Responsibility: Parse expressions and delegate to specialized boxes
// API: parse(src, i, ctx) -> JSON (delegates to parse_expr2)

using lang.compiler.parser.scan.parser_number_scan_box
using lang.compiler.parser.expr.parser_peek_box
using lang.compiler.parser.expr.parser_literal_box

static box ParserExprBox {
  parse_number2(src, i, ctx) {
    local pair = ParserNumberScanBox.scan_int(src, i)
    local at = pair.lastIndexOf("@")
    local json = pair.substring(0, at)
    local pos = i
    if at >= 0 { pos = ctx.to_int(pair.substring(at+1, pair.size())) }
    ctx.gpos_set(pos)
    return json
  }

  parse_string2(src, i, ctx) {
    local n = src.size()
    local j = i + 1
    local out = ""
    local guard = 0
    local max = 200000

    loop(j < n) {
      if guard > max { break }
      guard = guard + 1
      local ch = src.substring(j, j+1)

      if ch == "\"" {
        j = j + 1
        ctx.gpos_set(j)
        return "{\"type\":\"Str\",\"value\":\"" + ctx.esc_json(out) + "\"}"
      }

      if ch == "\\" && j + 1 < n {
        local nx = src.substring(j+1, j+2)
        if nx == "\"" { out = out + "\"" j = j + 2 }
        else { if nx == "\\" { out = out + "\\" j = j + 2 }
        else { if nx == "n" { out = out + "\n" j = j + 2 }
        else { if nx == "r" { out = out + "\r" j = j + 2 }
        else { if nx == "t" { out = out + "\t" j = j + 2 }
        else { if nx == "u" && j + 5 < n { out = out + src.substring(j, j+6) j = j + 6 }
        else { out = out + nx j = j + 2 } } } } } }
      } else {
        out = out + ch
        j = j + 1
      }
    }

    ctx.gpos_set(j)
    return "{\"type\":\"Str\",\"value\":\"" + ctx.esc_json(out) + "\"}"
  }

  parse_factor2(src, i, ctx) {
    local j = ctx.skip_ws(src, i)
    if j >= src.size() {
      ctx.gpos_set(j)
      return "{\"type\":\"Int\",\"value\":0}"
    }

    if ctx.starts_with_kw(src, j, "true") == 1 {
      ctx.gpos_set(j + 4)
      return "{\"type\":\"Bool\",\"value\":true}"
    }

    if ctx.starts_with_kw(src, j, "false") == 1 {
      ctx.gpos_set(j + 5)
      return "{\"type\":\"Bool\",\"value\":false}"
    }

    if ctx.starts_with_kw(src, j, "null") == 1 {
      ctx.gpos_set(j + 4)
      return "{\"type\":\"Null\"}"
    }

    // Peek expression: delegate to ParserPeekBox
    if ctx.starts_with_kw(src, j, "peek") == 1 {
      j = j + 4
      return ParserPeekBox.parse(src, j, ctx)
    }

    local ch = src.substring(j, j+1)

    // Parenthesized
    if ch == "(" {
      local inner = me.parse_expr2(src, j + 1, ctx)
      local k = ctx.gpos_get()
      k = ctx.skip_ws(src, k)
      if src.substring(k, k+1) == ")" { k = k + 1 }
      ctx.gpos_set(k)
      return inner
    }

    // String literal
    if ch == "\"" {
      return me.parse_string2(src, j, ctx)
    }

    // Map literal: delegate to ParserLiteralBox
    if ch == "{" {
      return ParserLiteralBox.parse_map(src, j, ctx)
    }

    // Array literal: delegate to ParserLiteralBox
    if ch == "[" {
      return ParserLiteralBox.parse_array(src, j, ctx)
    }

    // new Class(args)
    if ctx.starts_with_kw(src, j, "new") == 1 {
      local p = ctx.skip_ws(src, j + 3)
      local idp = ctx.read_ident2(src, p)
      local at = idp.lastIndexOf("@")
      local cls = idp.substring(0, at)
      local k = ctx.to_int(idp.substring(at+1, idp.size()))
      k = ctx.skip_ws(src, k)
      if src.substring(k, k+1) == "(" { k = k + 1 }
      local args_and_pos = me.parse_args2(src, k, ctx)
      local at2 = args_and_pos.lastIndexOf("@")
      local args_json = args_and_pos.substring(0, at2)
      k = ctx.to_int(args_and_pos.substring(at2+1, args_and_pos.size()))
      k = ctx.skip_ws(src, k)
      if src.substring(k, k+1) == ")" { k = k + 1 }
      ctx.gpos_set(k)
      return "{\"type\":\"New\",\"class\":\"" + cls + "\",\"args\":" + args_json + "}"
    }

    // Identifier / Call / Method chain
    if ctx.is_alpha(ch) {
      local idp = ctx.read_ident2(src, j)
      local at = idp.lastIndexOf("@")
      local name = idp.substring(0, at)
      local k = ctx.to_int(idp.substring(at+1, idp.size()))
      local node = "{\"type\":\"Var\",\"name\":\"" + name + "\"}"
      local cont2 = 1

      loop(cont2 == 1) {
        k = ctx.skip_ws(src, k)
        local tch = src.substring(k, k+1)

        if tch == "(" {
          k = k + 1
          local args_and_pos = me.parse_args2(src, k, ctx)
          local at2 = args_and_pos.lastIndexOf("@")
          local args_json = args_and_pos.substring(0, at2)
          k = ctx.to_int(args_and_pos.substring(at2+1, args_and_pos.size()))
          k = ctx.skip_ws(src, k)
          if src.substring(k, k+1) == ")" { k = k + 1 }
          node = "{\"type\":\"Call\",\"name\":\"" + name + "\",\"args\":" + args_json + "}"
        } else {
          if tch == "." {
            k = k + 1
            k = ctx.skip_ws(src, k)
            local midp = ctx.read_ident2(src, k)
            local at3 = midp.lastIndexOf("@")
            local mname = midp.substring(0, at3)
            k = ctx.to_int(midp.substring(at3+1, midp.size()))
            k = ctx.skip_ws(src, k)
            if src.substring(k, k+1) == "(" { k = k + 1 }
            local args2 = me.parse_args2(src, k, ctx)
            local at4 = args2.lastIndexOf("@")
            local args_json2 = args2.substring(0, at4)
            k = ctx.to_int(args2.substring(at4+1, args2.size()))
            k = ctx.skip_ws(src, k)
            if src.substring(k, k+1) == ")" { k = k + 1 }
            node = "{\"type\":\"Method\",\"recv\":" + node + ",\"method\":\"" + mname + "\",\"args\":" + args_json2 + "}"
          } else if tch == "[" {
            // Index access: node[ index ] → Method(recv=node, method="get", args=[index])
            k = k + 1
            k = ctx.skip_ws(src, k)
            local idx_json = ctx.parse_expr2(src, k)
            k = ctx.gpos_get()
            k = ctx.skip_ws(src, k)
            if src.substring(k, k+1) == "]" { k = k + 1 }
            local args_idx = "[" + idx_json + "]"
            node = "{\\\"type\\\":\\\"Method\\\",\\\"recv\\\":" + node + ",\\\"method\\\":\\\"get\\\",\\\"args\\\":" + args_idx + "}"
          } else {
            cont2 = 0
          }
        }
      }

      ctx.gpos_set(k)
      return node
    }

    // Fallback: number
    return me.parse_number2(src, j, ctx)
  }

  parse_unary2(src, i, ctx) {
    local j = ctx.skip_ws(src, i)
    if src.substring(j, j+1) == "-" {
      local rhs = me.parse_factor2(src, j + 1, ctx)
      j = ctx.gpos_get()
      local zero = "{\"type\":\"Int\",\"value\":0}"
      ctx.gpos_set(j)
      return "{\"type\":\"Binary\",\"op\":\"-\",\"lhs\":" + zero + ",\"rhs\":" + rhs + "}"
    }
    return me.parse_factor2(src, j, ctx)
  }

  parse_term2(src, i, ctx) {
    local lhs = me.parse_unary2(src, i, ctx)
    local j = ctx.gpos_get()
    local cont = 1

    loop(cont == 1) {
      j = ctx.skip_ws(src, j)
      if j >= src.size() {
        cont = 0
      } else {
        local op = src.substring(j, j+1)
        if op != "*" && op != "/" {
          cont = 0
        } else {
          local rhs = me.parse_unary2(src, j+1, ctx)
          j = ctx.gpos_get()
          lhs = "{\"type\":\"Binary\",\"op\":\"" + op + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}"
        }
      }
    }

    ctx.gpos_set(j)
    return lhs
  }

  parse_sum2(src, i, ctx) {
    local lhs = me.parse_term2(src, i, ctx)
    local j = ctx.gpos_get()
    local cont = 1

    loop(cont == 1) {
      j = ctx.skip_ws(src, j)
      if j >= src.size() {
        cont = 0
      } else {
        local op = src.substring(j, j+1)
        if op != "+" && op != "-" {
          cont = 0
        } else {
          local rhs = me.parse_term2(src, j+1, ctx)
          j = ctx.gpos_get()
          lhs = "{\"type\":\"Binary\",\"op\":\"" + op + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}"
        }
      }
    }

    ctx.gpos_set(j)
    return lhs
  }

  parse_compare2(src, i, ctx) {
    local lhs = me.parse_sum2(src, i, ctx)
    local j = ctx.gpos_get()
    j = ctx.skip_ws(src, j)
    local two = src.substring(j, j+2)
    local one = src.substring(j, j+1)
    local op = ""

    if two == "==" || two == "!=" || two == "<=" || two == ">=" {
      op = two
      j = j + 2
    } else {
      if one == "<" || one == ">" {
        op = one
        j = j + 1
      }
    }

    if op == "" {
      ctx.gpos_set(j)
      return lhs
    }

    local rhs = me.parse_sum2(src, j, ctx)
    j = ctx.gpos_get()
    ctx.gpos_set(j)
    return "{\"type\":\"Compare\",\"op\":\"" + op + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}"
  }

  parse_expr2(src, i, ctx) {
    local lhs = me.parse_compare2(src, i, ctx)
    local j = ctx.gpos_get()
    local cont = 1

    loop(cont == 1) {
      j = ctx.skip_ws(src, j)
      local two = src.substring(j, j+2)
      if two != "&&" && two != "||" {
        cont = 0
      } else {
        local rhs = me.parse_compare2(src, j+2, ctx)
        j = ctx.gpos_get()
        lhs = "{\"type\":\"Logical\",\"op\":\"" + two + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}"
      }
    }

    j = ctx.skip_ws(src, j)
    if src.substring(j, j+1) == "?" {
      j = j + 1
      j = ctx.skip_ws(src, j)
      local then_expr = me.parse_expr2(src, j, ctx)
      j = ctx.gpos_get()
      j = ctx.skip_ws(src, j)
      if src.substring(j, j+1) == ":" { j = j + 1 }
      j = ctx.skip_ws(src, j)
      local else_expr = me.parse_expr2(src, j, ctx)
      j = ctx.gpos_get()
      if else_expr.size() == 0 { else_expr = "{\"type\":\"Int\",\"value\":0}" }
      ctx.gpos_set(j)
      return "{\"type\":\"Ternary\",\"cond\":" + lhs + ",\"then\":" + then_expr + ",\"else\":" + else_expr + "}"
    }

    ctx.gpos_set(j)
    return lhs
  }

  parse_args2(src, i, ctx) {
    local j = ctx.skip_ws(src, i)
    local n = src.size()
    local out = "["
    j = ctx.skip_ws(src, j)

    if j < n && src.substring(j, j+1) == ")" {
      return "[]@" + ctx.i2s(j)
    }

    // first argument
    local e = me.parse_expr2(src, j, ctx)
    j = ctx.gpos_get()
    out = out + e

    // subsequent arguments with guard
    local cont_args = 1
    local guard = 0
    local max = 100000

    loop(cont_args == 1) {
      if guard > max { cont_args = 0 } else { guard = guard + 1 }
      local before = j
      j = ctx.skip_ws(src, j)

      if j < n && src.substring(j, j+1) == "," {
        j = j + 1
        j = ctx.skip_ws(src, j)
        e = me.parse_expr2(src, j, ctx)
        j = ctx.gpos_get()
        out = out + "," + e
      } else {
        cont_args = 0
      }

      if j == before { cont_args = 0 }
    }

    out = out + "]"
    return out + "@" + ctx.i2s(j)
  }
}