package core

import (
	"TsDB2/DB/core/index/btree"
	"TsDB2/DB/core/page"
	"TsDB2/DB/core/types"
	"TsDB2/DB/core/util"
	"unsafe"
)

type TablePage struct {
	hdr    page.PageHdr
	tables []*Table

	handle        page.HandleDb
	hdrSize       uint32 // hdr 的大小
	tableInfoSize uint32 // 表头大小
	lastPageID    uint32 // 最后一页
}

// NewTablePage 创建表页管理器
func NewTablePage(handle page.HandleDb) *TablePage {
	return &TablePage{
		handle:        handle,
		hdrSize:       uint32(unsafe.Sizeof(page.PageHdr{})),
		tableInfoSize: uint32(unsafe.Sizeof(TableInfo{})),
	}
}

// Tables 获取所有表
func (t *TablePage) Tables() []*Table {
	return t.tables
}

// LastPageID 获取最后页ID
func (t *TablePage) LastPageID() uint32 {
	return t.lastPageID
}

// Init 初始化表页：从磁盘读取所有表 + 所有字段（支持跨页存储）
func (t *TablePage) Init(pageID uint32) {
	t.tables = make([]*Table, 0)
	t.hdrSize = uint32(unsafe.Sizeof(page.PageHdr{}))
	t.tableInfoSize = uint32(unsafe.Sizeof(TableInfo{}))
	t.hdr.PageID = pageID
	t.hdr.Type = page.TableIndex
	t.hdr.NextPage = 0
	t.lastPageID = 0

	if pageID == 0 {
		return
	}

	for pageID != 0 {
		t.lastPageID = pageID
		pageBuf := make([]byte, PageSize)
		if err := t.handle.ReadPage(pageID, pageBuf); err != nil {
			break
		}
		pageHdr := (*page.PageHdr)(unsafe.Pointer(&pageBuf[0]))
		offset := t.hdrSize

		for offset+t.tableInfoSize <= pageHdr.UseSize {
			info := (*TableInfo)(unsafe.Pointer(&pageBuf[offset]))
			if util.IsHighBitSet(info.Flag) {
				offset += t.tableInfoSize + uint32(info.FieldAllocateSize)
				continue
			}

			activeVer, masterFields, versions, fieldOffset := readSchema(
				t.handle, pageID, uint16(offset+t.tableInfoSize), info.FieldAllocateSize)
			indexMate := &IndexMetaPage{
				handle: t.handle,
			}
			indexMate.Init(info.FirstIndexID)
			t.tables = append(t.tables, &Table{
				info:             info,
				Field:            masterFields,
				handle:           t.handle,
				indexMeta:        indexMate,
				tablePageID:      pageID,
				tableStartOffset: offset,
				curOffset:        fieldOffset,
				activeVersion:    activeVer,
				versions:         versions,
			})

			offset += t.tableInfoSize + uint32(info.FieldAllocateSize)
		}
		pageID = pageHdr.NextPage
	}
}

// ===========================================================================
// ✅ Create 完整正确（字段数量全是 byte，255上限）
// ===========================================================================
func (t *TablePage) Create(name string, fields []types.FieldInfo) (*Table, error) {
	fieldCount := byte(len(fields))

	if len(name) > TableNameSize {
		return nil, ErrTableNameTooLong
	}
	for _, tb := range t.tables {
		if util.BytesToString(tb.info.Name[:]) == name && !util.IsHighBitSet(tb.info.Flag) {
			return nil, ErrTableExists
		}
	}
	if fieldCount == 0 || int(fieldCount)+1 >= MaxFieldSize {
		return nil, ErrInvalidFieldCount
	}

	realFieldSize := uint32(1) // 字段数量：1字节(byte)
	for _, f := range fields {
		realFieldSize += 2 + uint32(len(f.FieldName))
	}
	allocateSize := realFieldSize * 2
	if allocateSize < MinFieldAllocateSize {
		allocateSize = MinFieldAllocateSize
	}
	if allocateSize > PageSize {
		return nil, ErrFieldAllocateTooLarge
	}

	var pageBuf []byte
	var pageHdr *page.PageHdr

	if t.hdr.PageID == 0 {
		pid := t.handle.NewPage()
		pageBuf, pageHdr = t.InitHeader(pid)
		t.hdr.PageID = pid
		t.lastPageID = pid
	} else {
		pageBuf = make([]byte, PageSize)
		t.handle.ReadPage(t.lastPageID, pageBuf)
		pageHdr = (*page.PageHdr)(unsafe.Pointer(&pageBuf[0]))
	}

	// 当前已经使用了的
	offset := pageHdr.UseSize
	// 这个表总共需要多少空间
	required := t.tableInfoSize + uint32(allocateSize)

	// 表空间不足就创建新的页存表
	if offset+required > PageSize {
		newPID := t.handle.NewPage()
		newBuf, newHdr := t.InitHeader(newPID)
		pageHdr.NextPage = newPID
		t.handle.SavePage(t.lastPageID, pageBuf) // 保存旧页的 NextPage 更新

		t.lastPageID = newPID
		pageBuf = newBuf
		pageHdr = newHdr
		offset = t.hdrSize
	}

	info := (*TableInfo)(unsafe.Pointer(&pageBuf[offset]))
	copy(info.Name[:], name)
	info.Flag = 0
	info.FieldCount = fieldCount
	info.ActiveFieldCount = fieldCount // 初始时实际字段数等于总字段数
	info.RowSize = types.CalcRowSize(fields)
	info.FieldAllocateSize = uint16(allocateSize)
	info.TotalRows = 0

	// 创建数据页
	dataPID := t.handle.NewPage()
	info.FirstData = dataPID
	info.LastData = dataPID
	dataBuf := make([]byte, PageSize)
	dHdr := (*page.PageHdr)(unsafe.Pointer(&dataBuf[0]))
	dHdr.Type = page.DataIndex
	dHdr.PageID = dataPID
	dHdr.UseSize = t.hdrSize
	t.handle.SavePage(dataPID, dataBuf)

	// 创建堆页
	heapPID := t.handle.NewPage()
	info.FirstHeap = heapPID
	info.LastHeap = heapPID
	heapBuf := make([]byte, PageSize)
	hHdr := (*page.PageHdr)(unsafe.Pointer(&heapBuf[0]))
	hHdr.Type = page.HeapIndex
	hHdr.PageID = heapPID
	hHdr.UseSize = t.hdrSize
	t.handle.SavePage(heapPID, heapBuf)

	indexMate := &IndexMetaPage{
		handle: t.handle,
	}
	// 创建索引元数据
	indexPID := t.handle.NewPage()
	indexMate.Init(indexPID)
	indexMate.InitHeader(indexPID)
	info.FirstIndexID = indexPID
	info.LastIndexID = indexPID

	// ==========================
	// 写新版 schema 字段定义链
	// 格式: [activeVer(1B)] [masterCount(1B)] [type+len+name]×N [verCount(1B)] [ver1...]
	// ==========================
	fieldOff := offset + t.tableInfoSize
	wo := fieldOff

	// activeVer = 1
	pageBuf[wo] = 1
	wo++
	// masterCount
	pageBuf[wo] = fieldCount
	wo++
	// master fields
	masterIndices := make([]byte, fieldCount)
	for i, f := range fields {
		pageBuf[wo] = byte(f.FieldType)
		pageBuf[wo+1] = byte(len(f.FieldName))
		wo += 2
		copy(pageBuf[wo:], f.FieldName)
		wo += uint32(len(f.FieldName))
		masterIndices[i] = byte(i)
	}
	// verCount = 1
	pageBuf[wo] = 1
	wo++
	// version 1 definition
	pageBuf[wo] = 1 // verNo
	wo++
	pageBuf[wo] = fieldCount
	wo++
	copy(pageBuf[wo:], masterIndices)
	wo += uint32(len(masterIndices))

	pageHdr.UseSize = offset + required
	t.handle.SavePage(t.lastPageID, pageBuf)

	// 构建初始 SchemaVersion
	initialVersions := []SchemaVersion{{Version: 1, FieldIndices: masterIndices}}

	newTable := Table{
		info:             info,
		Field:            fields,
		handle:           t.handle,
		indexMeta:        indexMate,
		tablePageID:      t.lastPageID,
		tableStartOffset: offset,
		curOffset:        FieldOffset{PageID: t.lastPageID, StartOffset: uint16(fieldOff), EndOffset: uint16(wo - fieldOff)},
		activeVersion:    1,
		versions:         initialVersions,
	}
	t.tables = append(t.tables, &newTable)
	return &newTable, nil
}

// ===========================================================================
// ✅ Drop 删除表并回收所有页
// ===========================================================================
func (t *TablePage) Drop(name string) error {
	pageID := t.hdr.PageID

	for pageID != 0 {
		buf := make([]byte, PageSize)
		if err := t.handle.ReadPage(pageID, buf); err != nil {
			return err
		}

		hdr := (*page.PageHdr)(unsafe.Pointer(&buf[0]))
		offset := t.hdrSize
		for offset+t.tableInfoSize <= hdr.UseSize {
			info := (*TableInfo)(unsafe.Pointer(&buf[offset]))
			if util.BytesToString(info.Name[:]) == name && !util.IsHighBitSet(info.Flag) {
				// 找到该表在内存中的 Table 对象，获取其索引元数据
				var tableEntry *Table
				for _, tb := range t.tables {
					if util.BytesToString(tb.info.Name[:]) == name && !util.IsHighBitSet(tb.info.Flag) {
						tableEntry = tb
						break
					}
				}
				// 回收该表所有页 (用该表自己的 indexMeta.metas，不遍历共享的 IndexMeta 页链)
				t.recycleTablePages(info, tableEntry)
				// 软删除标记
				info.Flag = util.SetHighBit(info.Flag)
				t.handle.SavePage(pageID, buf)
				for i := range t.tables {
					if util.BytesToString(t.tables[i].info.Name[:]) == name {
						t.tables = append(t.tables[:i], t.tables[i+1:]...)
						break
					}
				}
				return nil
			}
			offset += t.tableInfoSize + uint32(info.FieldAllocateSize)
		}
		pageID = hdr.NextPage
	}
	return ErrTableNotFound
}

// recycleTablePages 回收表的所有页 (B+树页、DataPage页、Heap页)
// 注意: IndexMeta 页是所有表共享的，不能释放！
func (t *TablePage) recycleTablePages(info *TableInfo, tableEntry *Table) {
	if t.handle.FreePage == nil {
		return
	}

	var pagesToFree []uint32

	// 1. 用该表自己的 indexMeta.metas 收集 B+ 树页和 DataPage
	//    不遍历共享的 IndexMeta 页链，避免误释放其他表的索引页
	if tableEntry != nil && tableEntry.indexMeta != nil {
		for i := range tableEntry.indexMeta.metas {
			m := &tableEntry.indexMeta.metas[i]
			if m.Flag&0x80 != 0 || m.EntryPage == 0 {
				continue
			}
			// 收集 B+ 树所有节点页 (内部节点+叶子节点)
			btPages := btree.CollectAllPageIDs(t.handle, m.EntryPage)
			pagesToFree = append(pagesToFree, btPages...)
			// 只有主键/时序索引的叶子节点存 DataPage ID
			// 二级索引叶子存的是 PKID(8B)，不是 DataPage ID！
			if m.IndexType == page.IndexTypePrimary || m.IndexType == page.IndexTypeTime {
				dpIDs := btree.GetDataPageIDs(t.handle, m.EntryPage)
				pagesToFree = append(pagesToFree, dpIDs...)
			}
		}
	}

	// 2. 收集 Heap 页链 (溢出页)
	heapID := info.FirstHeap
	for heapID != 0 {
		buf := make([]byte, PageSize)
		if err := t.handle.ReadPage(heapID, buf); err != nil {
			break
		}
		hdr := (*page.PageHdr)(unsafe.Pointer(&buf[0]))
		nextHeap := hdr.NextPage
		pagesToFree = append(pagesToFree, heapID)
		heapID = nextHeap
	}

	// 3. 收集 Overflow 页链
	oflowID := info.FirstOverflow
	for oflowID != 0 {
		buf := make([]byte, PageSize)
		if err := t.handle.ReadPage(oflowID, buf); err != nil {
			break
		}
		hdr := (*page.PageHdr)(unsafe.Pointer(&buf[0]))
		nextOflow := hdr.NextPage
		pagesToFree = append(pagesToFree, oflowID)
		oflowID = nextOflow
	}

	// 4. 统一释放所有页
	for _, pid := range pagesToFree {
		t.handle.FreePage(pid)
	}
}

func (t *TablePage) Find(name string) (*Table, bool) {
	for i := range t.tables {
		tb := t.tables[i]
		if util.BytesToString(tb.info.Name[:]) == name && !util.IsHighBitSet(tb.info.Flag) {
			return tb, true
		}
	}
	return nil, false
}

// InitHeader 初始化头部信息
func (t *TablePage) InitHeader(pageID uint32) ([]byte, *page.PageHdr) {
	newBuf := make([]byte, PageSize)
	newHdr := (*page.PageHdr)(unsafe.Pointer(&newBuf[0]))
	newHdr.Type = page.TableIndex
	newHdr.PageID = pageID
	newHdr.UseSize = uint32(unsafe.Sizeof(*newHdr))
	t.handle.SavePage(pageID, newBuf)
	return newBuf, newHdr
}