//go:build ignore

package main

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"os"
)

var output bytes.Buffer

func fprintf(format string, args ...interface{}) {
	_, _ = fmt.Fprintf(&output, format, args...)
}

func main() {
	f, _ := parser.ParseFile(token.NewFileSet(), "./../database.go", nil, 0)
	fprintf("// Code generated by mkrw.go; DO NOT EDIT.\n\n")
	fprintf("package leveldb\n\n")
	fprintf("import \"github.com/Mrs4s/go-cqhttp/db\"\n\n")
	ast.Inspect(f, func(node ast.Node) bool {
		switch node := node.(type) {
		case *ast.FuncDecl:
			return false
		case *ast.TypeSpec:
			if !node.Name.IsExported() {
				return false
			}
			x, ok := node.Type.(*ast.StructType)
			if !ok {
				return false
			}
			if x.Fields != nil && x.Fields.List != nil {
				mkWrite(node)
				mkRead(node)
			}
		}
		return true
	})
	out, err := format.Source(output.Bytes())
	if err != nil {
		fmt.Println(string(output.Bytes()))
		panic(err)
	}
	os.WriteFile("database_gen.go", out, 0o644)
}

func typeName(typ ast.Expr) string {
	switch typ := typ.(type) {
	case *ast.Ident:
		return typ.Name
	case *ast.ArrayType:
		if typ.Len != nil {
			panic("unexpected array type")
		}
		return "[]" + typeName(typ.Elt)
	case *ast.SelectorExpr:
		return typeName(typ.X) + "." + typ.Sel.Name
	}
	panic("unexpected type")
}

func mkWrite(node *ast.TypeSpec) {
	typename := node.Name.String()
	structType := node.Type.(*ast.StructType)
	fprintf("func (w *writer) write%s(x *db.%s) {\n", typename, typename)
	fprintf("if x == nil {\n")
	fprintf("w.nil()\n")
	fprintf("return\n")
	fprintf("}\n")
	fprintf("w.coder(coderStruct)\n")
	for _, field := range structType.Fields.List {
		switch typ := field.Type.(type) {
		case *ast.Ident:
			for _, name := range field.Names {
				fprintf("w.%s(x.%s)\n", typ.Name, name.Name)
			}
		case *ast.ArrayType:
			if typeName(typ) != "[]global.MSG" {
				panic("unexpected array type")
			}
			for _, name := range field.Names {
				fprintf("w.arrayMsg(x.%s)\n", name.Name)
			}
		case *ast.StarExpr:
			for _, name := range field.Names {
				fprintf("w.write%s(x.%s)\n", typeName(typ.X), name.Name)
			}
		}
	}
	fprintf("}\n\n")
}

func mkRead(node *ast.TypeSpec) {
	typename := node.Name.String()
	structType := node.Type.(*ast.StructType)
	fprintf(`func (r *reader) read%s() *db.%s {
	coder := r.coder()
	if coder == coderNil {
		return nil
	}`+"\n", typename, typename)
	fprintf("x := &db.%s{}\n", typename)
	for _, field := range structType.Fields.List {
		switch typ := field.Type.(type) {
		case *ast.Ident:
			for _, name := range field.Names {
				fprintf("x.%s = r.%s()\n", name.Name, typ.Name)
			}
		case *ast.ArrayType:
			if typeName(typ) != "[]global.MSG" {
				panic("unexpected array type")
			}
			for _, name := range field.Names {
				fprintf("x.%s = r.arrayMsg()\n", name.Name)
			}
		case *ast.StarExpr:
			for _, name := range field.Names {
				fprintf("x.%s = r.read%s()\n", name.Name, typeName(typ.X))
			}
		}
	}
	fprintf("return x\n")
	fprintf("}\n\n")
}