// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

//go:build linux && amd64

package debug

import (
	"fmt"
	"strings"

	"golang.org/x/arch/x86/x86asm"
)

// Disassemble decodes the instruction at the given address in the debuggee's
// memory and returns its text representation and length in bytes.
func (s *Session) Disassemble(addr uint64) (string, int, error) {
	// Read up to 15 bytes (max x86 instruction length).
	mem, err := s.ReadMemory(addr, 15)
	if err != nil {
		// Try a shorter read if we're near a page boundary.
		mem, err = s.ReadMemory(addr, 1)
		if err != nil {
			return "", 0, err
		}
	}
	inst, err := x86asm.Decode(mem, 64)
	if err != nil {
		return "???", 1, nil
	}
	text := x86asm.IntelSyntax(inst, addr, nil)
	return text, inst.Len, nil
}

// DisassembleN decodes up to n instructions starting at addr and returns
// them as a formatted string with addresses and byte offsets.
func (s *Session) DisassembleN(addr uint64, n int) string {
	var result strings.Builder
	pc := addr
	for range n {
		text, length, err := s.Disassemble(pc)
		if err != nil {
			result.WriteString(fmt.Sprintf("  %#08x: <error: %v>\n", pc, err))
			break
		}
		result.WriteString(fmt.Sprintf("  %#08x: %s\n", pc, text))
		if length == 0 {
			length = 1
		}
		pc += uint64(length)
	}
	return result.String()
}