package web

import (
	"errors"
	"html/template"
	"text/template/parse"

	"tug/internal/transport/web/text"
)

func walkPipes(n parse.Node, f func(*parse.PipeNode)) {
	switch n := n.(type) {
	case *parse.ListNode:
		if n == nil {
			return
		}
		for _, c := range n.Nodes {
			walkPipes(c, f)
		}
	case *parse.ActionNode:
		f(n.Pipe)
	case *parse.IfNode:
		f(n.Pipe)
		walkPipes(n.List, f)
		walkPipes(n.ElseList, f)
	case *parse.RangeNode:
		f(n.Pipe)
		walkPipes(n.List, f)
		walkPipes(n.ElseList, f)
	case *parse.WithNode:
		f(n.Pipe)
		walkPipes(n.List, f)
		walkPipes(n.ElseList, f)
	case *parse.TemplateNode:
		f(n.Pipe)
	}
}

func templateKeys(tpl *template.Template) []text.Key {
	var keys []text.Key
	for _, tt := range tpl.Templates() {
		if tt.Tree == nil {
			continue
		}
		walkPipes(tt.Tree.Root, func(p *parse.PipeNode) {
			if p == nil {
				return
			}
			for _, c := range p.Cmds {
				if len(c.Args) < 2 {
					continue
				}
				id, ok := c.Args[0].(*parse.IdentifierNode)
				if !ok || (id.Ident != "t" && id.Ident != "tr" && id.Ident != "trt") {
					continue
				}
				if s, ok := c.Args[1].(*parse.StringNode); ok {
					keys = append(keys, text.Key(s.Text))
				}
			}
		})
	}
	return keys
}

func checkKeys(tpl *template.Template) error {
	for _, k := range templateKeys(tpl) {
		if _, err := lookup(k); err != nil {
			return err
		}
	}
	return nil
}

var errNoPage = errors.New("no such page template")