package main

import (
	"go/ast"
	"go/importer"
	"go/parser"
	"go/token"
	"go/types"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"gitlab.wow.st/gmp/persist/generate"
)

func trimType(n *string) {
	*n = pkgreg.ReplaceAllString(*n,"")
	*n = treg.ReplaceAllString(*n,"")
}

func (v *visitor) Visit(node ast.Node) ast.Visitor {
	x, ok := node.(*ast.CallExpr); 	if !ok { return v }
	id,ok := x.Fun.(*ast.Ident);	if !ok { return v }

	if !reg.MatchString(id.Name) { return v }

	if len(x.Args) < 2 {
		log.Fatal("Wrong number of arguments in persistT call.")
	}
	var tp string
	switch arg := x.Args[1].(type) {
	case *ast.BasicLit:
		tp = strings.ToLower(arg.Kind.String())
		if tp == "float" {
			tp = "float64"
		}
	case *ast.CompositeLit:
		tp = types.TypeString(v.info.TypeOf(arg),types.RelativeTo(v.pkg))
	case *ast.Ident:
		tp = types.TypeString(v.info.TypeOf(arg),types.RelativeTo(v.pkg))
		trimType(&tp)
		for _, s := range impreg.FindAllStringSubmatchIndex(tp, -1) {
			pkgname := impreg.ExpandString(make([]byte,0), "$1", tp, s)
			v.needImps[string(pkgname)] = true
		}
	default:
	}

	name := reg.ReplaceAllString(id.Name,"$1")
	v.ts[name] = tps{fun: id.Name, name: name, typ: tp}
	return nil
}

type tps struct {
	fun,name,typ string
}

type visitor struct {
	pkg *types.Package
	ts map[string]tps
	imps map[string]string
	needImps map[string]bool
	info *types.Info
}

var (
	fset *token.FileSet
	reg, pkgreg, impreg, treg *regexp.Regexp
)

func newVisitor() *visitor {
	var v = &visitor{}
	v.imps = make(map[string]string)
	v.needImps = make(map[string]bool)
	v.info = &types.Info{
		Types:	make(map[ast.Expr]types.TypeAndValue),
		Defs:	make(map[*ast.Ident]types.Object),
		Uses:	make(map[*ast.Ident]types.Object)}
	v.ts = make(map[string]tps)
	v.needImps = make(map[string]bool)
	return v
}

func chkpkg(p *ast.Package) (map[string]tps, []string) {
	fs := make([]*ast.File,0)
	for _,f := range p.Files {
		fs = append(fs,f)
	}

	conf := types.Config{Error: func(error) {}, Importer: importer.Default()}
	v := newVisitor()
	var err error
	v.pkg, err = conf.Check("main", fset, fs, v.info)
	if err != nil {
		log.Print("Check:",err)
	}
	for _,f := range fs {
		for _,is := range f.Imports {
			name := is.Path.Value
			shortName := pkgreg.ReplaceAllString(name,"")
			v.imps[shortName] = name
		}
		ast.Walk(v,f)
	}
	imps := make([]string,0)
	for shortName := range v.needImps {
		imps = append(imps,v.imps[shortName])
	}
	return v.ts, imps
}

func init() {
	reg = regexp.MustCompile("^persist([a-zA-Z_]+[a-zA-Z_0-9]*)")

	pkgreg = regexp.MustCompile(`[a-zA-Z_]+[a-zA-Z_0-9\.]*/|"`)
	impreg = regexp.MustCompile(`([a-zA-Z_]+[a-zA-Z_0-9]+)\.[a-zA-Z_]+[a-zA-Z_0-9]+`)
	treg = regexp.MustCompile(`untyped `)

	fset = token.NewFileSet()

	// clear out old generated files
	fs,err := filepath.Glob("pgen*.go")
	if err != nil {
		log.Fatal("Glob error")
	}
	for _,f := range(fs) {
		err := os.Remove(f)
		if err != nil && os.IsExist(err) {
			log.Fatal("Removing ",f,err)
		}
	}
}

func main() {
	pkgs, err := parser.ParseDir(fset, ".", nil, 0)
	if err != nil {
		log.Fatal("Parse:",err)
	}
	// run type checker on each package
	for _,pkg := range pkgs {
		log.Print("Processing package ",pkg.Name)
		ts,imps := chkpkg(pkg)
		if len(ts) == 0 {
			continue
		}
		g := generate.NewGenerator(pkg.Name)
		for _,v := range ts {
			g.Add(v.fun, v.name, v.typ)
		}
		g.Import(imps...)
		var of *os.File
		var err error
		if pkg.Name == "main" {
			of, err = os.Create("pgen.go")
		} else {
			oname := strings.Join([]string{"pgen_",pkg.Name,".go"},"")
			of, err = os.Create(oname)
		}
		if err != nil {
			log.Fatal("Cannot open output file: ",err)
		}
		// process template for each type identified and
		// generate output
		g.Save(of)
	}
}