package instr

import (
	"git.elyanpoujol.fr/elyan/central-arch/pkg/register"
	"git.elyanpoujol.fr/elyan/central-arch/pkg/simstate"
)

type Instr uint32
type InstrFormat uint32

const (
	A InstrFormat = iota
	B
	C
	D1
	D2
	E
)

func (instrf InstrFormat) String() string {
	switch instrf {
	case A:
		return "A"

	case B:
		return "B"

	case C:
		return "C"

	case D1:
		return "D1"

	case D2:
		return "D2"

	case E:
		return "E"
	}

	panic("unknown format")
}

type Cond uint32

const (
	AL  Cond = iota     // Always
	EQ                  // Equal, Z==1
	NEQ                 // Not Equal, Z==0
	UGE                 // Unsigned Greater or Equal, C==1
	CS  Cond = iota - 1 // Carry Set, C==1
	ULT                 // Unsigned Lower Than, C==0
	CC  Cond = iota - 2 // Carry Clear, C==0
	NEG                 // Negative, N==1
	POS                 // Positive, N==0
	VS                  // oVerflow Set, V==1
	VC                  // oVerflow Clear, V==0
	UGT                 // Unsigned Greater Than, C==1 && Z==0
	ULE                 // Unsigned Lower Than, C==0 && Z==1
	SGE                 // Signed Greater or Equal, N==V
	SLT                 // Signed Lower Than, N!=V
	SGT                 // Signed Greater Than, Z==0 && N==V
	SLE                 // Signed Lower or Equal, Z==1 && N!=V
)

type InstrFormatter func(*DecodedInstr) string

type InstrBehavior func(*DecodedInstr, simstate.SimState) error

type InstrDesc struct {
	VariantName string
	Mnemonic    string
	OpCode      uint32
	Format      InstrFormat
	Formatter   InstrFormatter
	Behavior    InstrBehavior
}

type StandardFormatFields struct {
	Condition Cond
	Rd        register.CpuRegister
	Rs1       register.CpuRegister
	Rs2       register.CpuRegister
	Imm       uint32
}

type SubsystemFormatFields struct {
	Reg register.CpuRegister
	Sid uint32
	Sre uint32
	Cmd uint32
}

type DecodedInstr struct {
	Format InstrFormat
	OpCode uint32
	// A, B, C, D1 and D2 formats fields
	StandardFormatFields
	// E format fields
	SubsystemFormatFields
}