//go:build sqlite_vtable || vtable

package vtab

import (
	"fmt"

	gosqlite3 "github.com/mattn/go-sqlite3"
)

// ─── 桥接层：Module → gosqlite3.Module ──────────────────────

type moduleAdapter struct {
	mod Module
}

func (a *moduleAdapter) Create(c *gosqlite3.SQLiteConn, args []string) (gosqlite3.VTab, error) {
	return a.build(c, args, true)
}

func (a *moduleAdapter) Connect(c *gosqlite3.SQLiteConn, args []string) (gosqlite3.VTab, error) {
	return a.build(c, args, false)
}

func (a *moduleAdapter) DestroyModule() {}

func (a *moduleAdapter) build(c *gosqlite3.SQLiteConn, args []string, isCreate bool) (gosqlite3.VTab, error) {
	declare := func(schema string) error { return c.DeclareVTab(schema) }

	var (
		table Table
		err   error
	)
	if isCreate {
		table, err = a.mod.Create(args, declare)
	} else {
		table, err = a.mod.Connect(args, declare)
	}
	if err != nil {
		return nil, err
	}

	base := &baseVtabAdapter{table: table}
	// if wt, ok := table.(WritableTable); ok {
	// 	return &writableVtabAdapter{baseVtabAdapter: base, wt: wt}, nil
	// }
	return base, nil
}

func NewModuleAdapter(mod Module) gosqlite3.Module {
	return &moduleAdapter{mod}
}

// ─── 桥接层：Table（只读）────────────────────────────────────

type planKey struct {
	idxNum int
	idxStr string
}

type baseVtabAdapter struct {
	table Table
	// plans 保存每个查询计划中 Used=true 的约束（按值传入顺序），
	// BestIndex 写入，Filter 通过 (idxNum, idxStr) 查询后绑定值。
	plans map[planKey][]ConstraintInfo
}

func (v *baseVtabAdapter) BestIndex(csts []gosqlite3.InfoConstraint, obs []gosqlite3.InfoOrderBy) (*gosqlite3.IndexResult, error) {
	ci := make([]ConstraintInfo, len(csts))
	for i, c := range csts {
		ci[i] = ConstraintInfo{Column: c.Column, Op: c.Op, Usable: c.Usable}
	}
	ob := make([]OrderByInfo, len(obs))
	for i, o := range obs {
		ob[i] = OrderByInfo{Column: o.Column, Desc: o.Desc}
	}

	out, err := v.table.BestIndex(ci, ob)
	if err != nil {
		return nil, err
	}

	// 按值传入顺序收集 Used=true 的约束，供 Filter 阶段绑定值。
	var usedCi []ConstraintInfo
	for i, used := range out.Used {
		if used {
			usedCi = append(usedCi, ci[i])
		}
	}
	if v.plans == nil {
		v.plans = make(map[planKey][]ConstraintInfo)
	}
	v.plans[planKey{out.IdxNum, out.IdxStr}] = usedCi

	return &gosqlite3.IndexResult{
		Used:           out.Used,
		IdxNum:         out.IdxNum,
		IdxStr:         out.IdxStr,
		AlreadyOrdered: out.AlreadyOrdered,
		EstimatedCost:  out.EstimatedCost,
		EstimatedRows:  out.EstimatedRows,
	}, nil
}

func (v *baseVtabAdapter) Disconnect() error { return v.table.Disconnect() }
func (v *baseVtabAdapter) Destroy() error    { return v.table.Destroy() }

func (v *baseVtabAdapter) Open() (gosqlite3.VTabCursor, error) {
	c, err := v.table.Open()
	if err != nil {
		return nil, err
	}
	return &cursorAdapter{cursor: c, adapter: v}, nil
}

// ─── 桥接层：WritableTable ────────────────────────────────────

// writableVtabAdapter 内嵌只读适配器并实现 gosqlite3.VTabUpdater，
// go-sqlite3 通过类型断言检测到该接口后会启用 INSERT/UPDATE/DELETE。
type writableVtabAdapter struct {
	*baseVtabAdapter
	wt WritableTable
}

func (v *writableVtabAdapter) Delete(rowid any) error {
	return v.wt.Delete(rowid)
}

func (v *writableVtabAdapter) Insert(rowid any, values []any) (int64, error) {
	// rowid 是 SQLite 建议的值（通常为 nil，由表自行决定）
	return v.wt.Insert(values)
}

func (v *writableVtabAdapter) Update(rowid any, values []any) error {
	return v.wt.Update(rowid, values)
}

// ─── 桥接层：Cursor ───────────────────────────────────────────

type cursorAdapter struct {
	cursor  Cursor
	adapter *baseVtabAdapter
}

func (c *cursorAdapter) Close() error { return c.cursor.Close() }
func (c *cursorAdapter) Next() error  { return c.cursor.Next() }
func (c *cursorAdapter) EOF() bool    { return c.cursor.EOF() }

func (c *cursorAdapter) Filter(idxNum int, idxStr string, vals []any) error {
	ci := c.adapter.plans[planKey{idxNum, idxStr}]
	constraints := make([]ConstraintInfo, len(vals))
	for i, val := range vals {
		constraints[i].Value = val
		if i < len(ci) {
			constraints[i].Column = ci[i].Column
			constraints[i].Op = ci[i].Op
			constraints[i].Usable = true
		}
	}
	return c.cursor.Filter(idxNum, constraints)
}

func (c *cursorAdapter) Rowid() (int64, error) { return c.cursor.Rowid() }

func (c *cursorAdapter) Column(ctx *gosqlite3.SQLiteContext, col int) error {
	val, err := c.cursor.Column(col)
	if err != nil {
		return err
	}
	resultValue(ctx, val)
	return nil
}

// resultValue 将 Go 值写入 SQLite 上下文。
func resultValue(ctx *gosqlite3.SQLiteContext, val any) {
	if val == nil {
		ctx.ResultNull()
		return
	}
	switch v := val.(type) {
	case int:
		ctx.ResultInt(v)
	case int32:
		ctx.ResultInt(int(v))
	case int64:
		ctx.ResultInt64(v)
	case float32:
		ctx.ResultDouble(float64(v))
	case float64:
		ctx.ResultDouble(v)
	case bool:
		if v {
			ctx.ResultInt(1)
		} else {
			ctx.ResultInt(0)
		}
	case string:
		ctx.ResultText(v)
	case []byte:
		ctx.ResultBlob(v)
	default:
		ctx.ResultText(fmt.Sprint(v))
	}
}