package parser

import (
	"fmt"
	"go/ast"
	"go/token"
	"strconv"

	"github.com/markbates/pkger"
	"github.com/markbates/pkger/here"
	"github.com/markbates/pkger/pkging"
)

type visitor func(node ast.Node) (w ast.Visitor)

func (v visitor) Visit(node ast.Node) ast.Visitor {
	return v(node)
}

// inspired by https://gist.github.com/cryptix/d1b129361cea51a59af2
type file struct {
	fset     *token.FileSet
	astFile  *ast.File
	filename string
	decls    map[string]string
	paths    []pkging.Path
}

func (f *file) walk(fn func(ast.Node) bool) {
	ast.Walk(walker(fn), f.astFile)
}

func (f *file) find() ([]pkging.Path, error) {
	if err := f.findDecals(); err != nil {
		return nil, err
	}
	if err := f.findOpenCalls(); err != nil {
		return nil, err
	}

	if err := f.findWalkCalls(); err != nil {
		return nil, err
	}

	if err := f.findImportCalls(); err != nil {
		return nil, err
	}

	return f.paths, nil
}

func (f *file) findDecals() error {
	// iterate over all declarations
	for _, d := range f.astFile.Decls {

		// log.Printf("#%d Decl: %+v\n", i, d)

		// only interested in generic declarations
		if genDecl, ok := d.(*ast.GenDecl); ok {

			// handle const's and vars
			if genDecl.Tok == token.CONST || genDecl.Tok == token.VAR {

				// there may be multiple
				// i.e. const ( ... )
				for _, cDecl := range genDecl.Specs {

					// havn't find another kind of spec then value but better check
					if vSpec, ok := cDecl.(*ast.ValueSpec); ok {
						// log.Printf("const ValueSpec: %+v\n", vSpec)

						// iterate over Name/Value pair
						for i := 0; i < len(vSpec.Names); i++ {
							// TODO: only basic literals work currently
							if i > len(vSpec.Values) || len(vSpec.Values) == 0 {
								break
							}
							switch v := vSpec.Values[i].(type) {
							case *ast.BasicLit:
								f.decls[vSpec.Names[i].Name] = v.Value
							default:
								// log.Printf("Name: %s - Unsupported ValueSpec: %+v\n", vSpec.Names[i].Name, v)
							}
						}
					}
				}
			}

		}
	}

	return nil
}

func (f *file) findOpenCalls() error {
	var err error
	f.walk(func(node ast.Node) bool {
		ce, ok := node.(*ast.CallExpr)
		if !ok {
			return true
		}

		exists := isPkgDot(ce.Fun, "pkger", "Open")
		if !(exists) || len(ce.Args) != 1 {
			return true
		}

		switch x := ce.Args[0].(type) {

		case *ast.BasicLit:
			s, err := strconv.Unquote(x.Value)
			if err != nil {
				err = nil
				return false
			}
			pt, err := pkger.Parse(s)
			if err != nil {
				err = err
				return false
			}
			f.paths = append(f.paths, pt)
		case *ast.Ident:
			val, ok := f.decls[x.Name]
			if !ok {
				//TODO: Add ERRORs list to file type and return after iteration!
				// log.Printf("Could not find identifier[%s] in decls map\n", x.Name)
				return true
			}
			s, err := strconv.Unquote(val)
			if err != nil {
				err = nil
				return false
			}
			pt, err := pkger.Parse(s)
			if err != nil {
				err = err
				return false
			}
			f.paths = append(f.paths, pt)

		default:
		}

		return true
	})
	return err
}

func (f *file) findWalkCalls() error {
	var err error
	f.walk(func(node ast.Node) bool {
		ce, ok := node.(*ast.CallExpr)
		if !ok {
			return true
		}

		exists := isPkgDot(ce.Fun, "pkger", "Walk")
		if !(exists) || len(ce.Args) != 2 {
			return true
		}

		switch x := ce.Args[0].(type) {

		case *ast.BasicLit:
			s, err := strconv.Unquote(x.Value)
			if err != nil {
				err = nil
				return false
			}
			pt, err := pkger.Parse(s)
			if err != nil {
				err = err
				return false
			}
			f.paths = append(f.paths, pt)
		case *ast.Ident:
			val, ok := f.decls[x.Name]
			if !ok {
				//TODO: Add ERRORs list to file type and return after iteration!
				// log.Printf("Could not find identifier[%s] in decls map\n", x.Name)
				return true
			}
			s, err := strconv.Unquote(val)
			if err != nil {
				err = nil
				return false
			}
			pt, err := pkger.Parse(s)
			if err != nil {
				err = err
				return false
			}
			f.paths = append(f.paths, pt)

		default:
		}

		return true
	})
	return err
}

func (f *file) findImportCalls() error {
	var err error
	f.walk(func(node ast.Node) bool {
		ce, ok := node.(*ast.ImportSpec)
		if !ok {
			return true
		}

		s, err := strconv.Unquote(ce.Path.Value)
		if err != nil {
			return false
		}
		info, err := here.Package(s)
		if err != nil {
			return false
		}
		fmt.Println(">>>TODO parser/visitor.go:216: info ", info)
		res, err := Parse(info)
		if err != nil {
			return false
		}
		fmt.Println(">>>TODO parser/visitor.go:224: res ", res)
		return true
	})
	return err
}

// helpers
// =======
func isPkgDot(expr ast.Expr, pkg, name string) bool {
	sel, ok := expr.(*ast.SelectorExpr)
	return ok && isIdent(sel.X, pkg) && isIdent(sel.Sel, name)
}

func isIdent(expr ast.Expr, ident string) bool {
	id, ok := expr.(*ast.Ident)
	return ok && id.Name == ident
}

// wrap a function to fulfill ast.Visitor interface
type walker func(ast.Node) bool

func (w walker) Visit(node ast.Node) ast.Visitor {
	if w(node) {
		return w
	}
	return nil
}