five/hbrdd/driver.go

// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// RDD (Replaceable Database Driver) interface definitions for Five.
//
// Design: Harbour's 101-method RDDFUNCS vtable → Go interface composition.
// Each interface is small and focused (Go philosophy).
// Drivers implement only what they need; BaseArea provides defaults.
//
// Inheritance via Go embedding:
//   BaseArea (WAAREA) → DBFArea → NTXArea / CDXArea
//
// Reference:
//   /mnt/d/harbour-core/include/hbapirdd.h (lines 640-816)
//   docs/rdd-architecture-spec.md
package hbrdd

import (
	"five/hbrt"
	"fmt"
	"strings"
	"sync"
)

// --- Driver registry ---

var (
	driversMu sync.RWMutex
	drivers   = map[string]Driver{}
)

// RegisterDriver registers an RDD driver by name.
func RegisterDriver(d Driver) {
	driversMu.Lock()
	drivers[strings.ToUpper(d.Name())] = d
	driversMu.Unlock()
}

// GetDriver returns a registered driver by name.
func GetDriver(name string) (Driver, error) {
	driversMu.RLock()
	d, ok := drivers[strings.ToUpper(name)]
	driversMu.RUnlock()
	if !ok {
		return nil, fmt.Errorf("unknown RDD driver: %s", name)
	}
	return d, nil
}

// --- Core interfaces ---

// Driver creates and opens work areas.
// Harbour: RDD node with RDDFUNCS table.
type Driver interface {
	Name() string
	Open(params OpenParams) (Area, error)
	Create(params CreateParams) (Area, error)
}

// OpenParams for opening an existing table.
type OpenParams struct {
	Path      string // file path (without extension)
	Alias     string // workarea alias
	Shared    bool   // shared access mode
	ReadOnly  bool   // read-only mode
	CodePage  string // code page name
}

// CreateParams for creating a new table.
type CreateParams struct {
	Path      string
	Alias     string
	Fields    []FieldInfo
	CodePage  string
}

// FieldInfo describes a database field.
// Harbour: DBFFIELD (32 bytes in file, this is the runtime representation)
type FieldInfo struct {
	Name     string // up to 10 chars (Harbour limit)
	Type     byte   // 'C', 'N', 'L', 'D', 'M', 'I', 'B', '@', '+', '=', '^', 'Y', etc.
	Len      int    // field length
	Dec      int    // decimal places
	Flags    byte   // 0x01=system, 0x02=nullable, 0x04=binary
}

// --- Area interface (WAAREA + DBF core) ---

// Area is the primary interface for accessing a database table.
// Harbour: AREAP with SELF_* macro dispatch.
type Area interface {
	// Identity
	Driver() Driver
	Alias() string
	SetAlias(string)

	// Lifecycle
	Close() error
	Flush() error

	// Movement — Harbour: hb_waBof, hb_waEof, hb_waFound, hb_waGoTo, etc.
	BOF() bool
	EOF() bool
	Found() bool
	GoTo(recNo uint32) error
	GoTop() error
	GoBottom() error
	Skip(count int64) error

	// Record info
	RecNo() uint32
	RecCount() (uint32, error)
	Deleted() bool

	// Field access — Harbour: SELF_FIELDCOUNT, SELF_GETVALUE, SELF_PUTVALUE
	FieldCount() int
	GetFieldInfo(index int) FieldInfo
	GetValue(fieldIndex int) (hbrt.Value, error)
	PutValue(fieldIndex int, val hbrt.Value) error

	// Record operations — Harbour: SELF_APPEND, SELF_DELETE, SELF_RECALL
	Append() error
	Delete() error
	Recall() error

	// Bulk operations
	Pack() error
	Zap() error

	// State — Harbour: hb_waSetFound, locate support
	SetFound(b bool)
	SetLocate(expr string, block func(*hbrt.Thread) bool)
	LocateBlock() func(*hbrt.Thread) bool

	// Filter
	SetFilter(expr string, block func(*hbrt.Thread) bool) error
	ClearFilter() error
	HasFilter() bool
}

// --- Optional interfaces (drivers implement as needed) ---

// Indexer provides index management and key-based seeking.
// Harbour: order* methods in RDDFUNCS (9 methods).
// Only DBFNTX and DBFCDX implement this.
type Indexer interface {
	// Order management
	OrderCreate(params OrderCreateParams) error
	OrderListAdd(path string) error
	OrderListClear() error
	OrderListFocus(tagName string) error
	OrderListRebuild() error
	OrderDestroy(tagName string) error
	OrderInfo(ordNo int) (*OrderInfo, error)

	// Key-based seeking — Harbour: SELF_SEEK
	Seek(key hbrt.Value, softSeek bool, findLast bool) (bool, error)
}

// OrderCreateParams for INDEX ON.
type OrderCreateParams struct {
	TagName    string // index tag name
	KeyExpr    string // key expression (e.g., "UPPER(lastname+firstname)")
	ForExpr    string // FOR condition (e.g., "active = .T.")
	FilePath   string // index file path
	Unique     bool
	Descending bool

	// KeyFunc is an optional compiled key evaluator. When non-nil, the
	// indexer calls it directly instead of going through MacroEval on the
	// KeyExpr string. gengo emits this as an inline Go closure that
	// mirrors the AST of the key expression — zero string parsing at
	// runtime, symbol lookups hoisted out of the loop.
	//
	// Contract: caller must position the workarea (GoTo) before calling.
	// Returns the key value for the current record.
	KeyFunc func() hbrt.Value
}

// OrderInfo holds information about an index order.
type OrderInfo struct {
	Name       string
	KeyExpr    string
	ForExpr    string
	Unique     bool
	Descending bool
	KeyCount   uint32
	Custom     bool
}

// Locker provides record and file locking.
// Harbour: SELF_LOCK, SELF_UNLOCK, SELF_RAWLOCK
type Locker interface {
	LockRecord(recNo uint32) (bool, error)
	UnlockRecord(recNo uint32) error
	LockFile() (bool, error)
	UnlockFile() error
	IsLocked(recNo uint32) bool
}

// Relater provides SET RELATION support.
// Harbour: SELF_SETREL, SELF_CLEARREL, SELF_FORCEREL
type Relater interface {
	SetRelation(child Area, keyExpr func(*hbrt.Thread) hbrt.Value, scoped bool) error
	ClearRelation() error
	ForceRel() error
	SyncChildren() error
}

// MemoHandler provides memo field read/write.
// Harbour: SELF_OPENMEMFILE, SELF_CLOSEMEMFILE, SELF_GETVALUEFILE, SELF_PUTVALUEFILE
type MemoHandler interface {
	OpenMemo(path string) error
	CloseMemo() error
	ReadMemo(blockNo uint32) ([]byte, error)
	WriteMemo(data []byte) (uint32, error)
}

// Scoper provides SET SCOPE support for index-based range queries.
type Scoper interface {
	SetScope(top, bottom hbrt.Value) error
	ClearScope() error
}