package iskra

import "git.smesh.lol/iskradb/lattice"

// NullLatticeRec mirrors lattice.NullRec for use in iskra without importing lattice everywhere.
const NullLatticeRec = lattice.NullRec

// KindToBranch maps a NodeKind to the iskradb branch it belongs to.
func KindToBranch(kind NodeKind) lattice.Branch {
	if kind.Has(KindFunc | KindMethod) {
		return lattice.Bverb
	}
	if kind.Has(KindType | KindPkg | KindImport | KindConst | KindVar) {
		return lattice.Bnoun
	}
	return lattice.Bmodifier
}

// otherBranches returns the two branches that are not b, in a stable order.
func otherBranches(b lattice.Branch) [2]lattice.Branch {
	switch b {
	case lattice.Bnoun:
		return [2]lattice.Branch{lattice.Bverb, lattice.Bmodifier}
	case lattice.Bverb:
		return [2]lattice.Branch{lattice.Bnoun, lattice.Bmodifier}
	default: // Bmodifier
		return [2]lattice.Branch{lattice.Bnoun, lattice.Bverb}
	}
}

// SetFormOnRecord stores form in rec.Inline (up to 23 bytes) or overflows
// into pool with rec.DataFile=1, rec.DataOff/DataLen pointing into pool.
func SetFormOnRecord(rec *lattice.Record, form string, pool *[]byte) {
	b := []byte(form)
	if len(b) <= 23 {
		copy(rec.Inline[:], b)
		rec.Inline[23] = byte(len(b)) // length in last byte
		rec.DataFile = 0
		rec.DataOff = 0
		rec.DataLen = 0
	} else {
		copy(rec.Inline[:23], b[:23])
		rec.Inline[23] = 0 // overflow marker: length=0 means overflow
		rec.DataFile = 1
		rec.DataOff = uint32(len(*pool))
		rec.DataLen = uint32(len(b))
		*pool = append(*pool, b...)
	}
}

// FormFromRecord retrieves the surface form from rec.
func FormFromRecord(rec *lattice.Record, pool []byte) string {
	if rec.Inline[23] != 0 {
		// inline: length stored in Inline[23]
		n := int(rec.Inline[23])
		return string(rec.Inline[:n])
	}
	if rec.DataFile == 1 && rec.DataLen > 0 {
		end := rec.DataOff + rec.DataLen
		if int(end) <= len(pool) {
			return string(pool[rec.DataOff:end])
		}
	}
	return ""
}