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

//go:build freebsd && riscv64

package debug

import (
	"fmt"
	"strings"

	"sourcedock.dev/petrbalvin/gasm-sdk/arch"
	"sourcedock.dev/petrbalvin/gasm-sdk/disasm"
)

// Disassemble decodes the instruction at the given address in the debuggee's
// memory and returns its text representation and length in bytes.  The read
// shrinks from 4 to 2 bytes when the full word crosses into unmapped memory:
// a compressed instruction at the mapping's end still fits the shorter
// window, and an instruction can never extend past the mapping that holds it.
func (s *Session) Disassemble(addr uint64) (string, int, error) {
	var lastErr error
	for _, n := range []int{4, 2} {
		mem, err := s.ReadMemory(addr, n)
		if err != nil {
			lastErr = err
			continue
		}
		ins, derr := disasm.Decode(arch.RISCV, mem, addr)
		if derr != nil {
			return "", 0, derr
		}
		return ins.Text, ins.Len, nil
	}
	return "", 0, lastErr
}

// 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()
}

// isCallInsn reports whether disassembled text (riscv64asm.GoSyntax) is a
// call.  GoSyntax renders jal and jalr calls as CALL; the native mnemonics
// are accepted too.  The first token must match exactly: a prefix test on
// "bl" would catch branches on other architectures, and jalr as ret prints
// RET, which must not be stepped over.
func isCallInsn(text string) bool {
	m, _, _ := strings.Cut(text, " ")
	switch strings.ToLower(m) {
	case "call", "jal", "jalr":
		return true
	}
	return false
}