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

// Package ast defines the abstract syntax tree of a GAsm source file.  The
// tree is produced by the parser and consumed by the formatter, linter and
// language server.  Operand classification that depends on the target
// architecture (is this bare name a register or a label?) is deliberately left
// to the arch package; the AST records syntax only.
package ast

import "sourcedock.dev/petrbalvin/gasm-devkit/token"

// File is the parsed representation of one .s source file.
type File struct {
	Path    string
	Decls   []Decl
	Orphans []Stmt // labels/instructions seen before any TEXT directive
	// Macros holds the names introduced by #define directives in this file.
	// The linter uses it to avoid flagging macro invocations as unknown
	// instructions (macro expansion itself is out of scope, see the docs).
	Macros map[string]bool
}

// Decl is a top-level declaration.
type Decl interface {
	declNode()
	// Pos returns the position of the declaration's first token.
	Pos() token.Position
}

// Stmt is a statement inside a TEXT body.
type Stmt interface {
	stmtNode()
	Pos() token.Position
}

// Include is a #include "header" line.
type Include struct {
	Hash   token.Token
	Name   token.Token // the directive name, usually "include"
	Header token.Token // the string literal, quotes included
}

func (*Include) declNode()             {}
func (d *Include) Pos() token.Position { return d.Hash.Pos }

// Preproc is any other preprocessor line (#define, #undef, …) captured loosely.
type Preproc struct {
	Hash token.Token
	Raw  string // verbatim text after the '#'
}

func (*Preproc) declNode()             {}
func (d *Preproc) Pos() token.Position { return d.Hash.Pos }

// Text is a TEXT function definition and its body.
type Text struct {
	Keyword token.Token // the TEXT token
	Name    *Symbol     // ·funcName(SB)
	Flags   []string    // NOSPLIT, DUPOK, …
	Frame   *Operand    // $0
	Args    *Operand    // the -65 part; nil when absent
	Body    []Stmt
	Doc     string // preceding comment block (typically the Go signature)
}

func (*Text) declNode()             {}
func (d *Text) Pos() token.Position { return d.Keyword.Pos }

// Globl is a GLOBL symbol declaration.
type Globl struct {
	Keyword token.Token
	Name    *Symbol
	Flags   []string
	Size    *Operand
}

func (*Globl) declNode()             {}
func (d *Globl) Pos() token.Position { return d.Keyword.Pos }

// Data is a DATA symbol initialiser.
type Data struct {
	Keyword token.Token
	Name    *Symbol // includes any +offset
	Width   int     // the /width suffix; 0 when absent
	Value   *Operand
}

func (*Data) declNode()             {}
func (d *Data) Pos() token.Position { return d.Keyword.Pos }

// Label is a local label definition such as vec1:.
type Label struct {
	Name  token.Token
	Colon token.Token
}

func (*Label) stmtNode()             {}
func (s *Label) Pos() token.Position { return s.Name.Pos }

// Instr is a single machine instruction with zero or more operands.
type Instr struct {
	Mnemonic token.Token
	Operands []*Operand
	Comment  string // trailing comment text, without the leading //
}

func (*Instr) stmtNode()             {}
func (s *Instr) Pos() token.Position { return s.Mnemonic.Pos }

// Symbol is a symbol reference: ·name(SB), name<>(SB), name+8(FP), …
type Symbol struct {
	Raw    string // verbatim text
	Pkg    string // package prefix before the middle dot ("" = current package)
	Name   string // identifier without the middle dot or <>
	Static bool   // the <> marker is present
	Pseudo string // FP, SP, SB or PC ("" for a bare name)
	Offset int64
	HasOff bool
	Pos    token.Position
}

// OpKind classifies an operand syntactically.
type OpKind int

const (
	OpImmediate = iota // $value
	OpAddr             // register, memory reference, symbol or label
)

// Operand is one instruction operand.
type Operand struct {
	Raw  string
	Kind OpKind
	Imm  Immediate
	Addr Address
	Pos  token.Position
}

// Immediate is a $ value.
type Immediate struct {
	Neg    bool
	Val    int64
	HasVal bool    // a simple integer immediate was parsed
	Float  string  // non-empty for a floating-point immediate
	Str    string  // non-empty for a string/rune immediate
	Sym    *Symbol // non-nil for $sym(…)
}

// Address is a non-immediate operand: a register, a memory reference, a symbol
// reference or a label.  Fields are populated best-effort from the syntax.
type Address struct {
	Sym    *Symbol // name reference (bare ident, or name+off(pseudo))
	Base   string  // base register, from (base)
	Index  string  // index register, from (index*scale)
	Scale  int     // index scale; 0 when absent
	Offset int64   // leading displacement, from off(base)
	HasOff bool    // a leading displacement is present
	Shift  string  // verbatim arm64 shift suffix, e.g. "<<2"
}