package main

import (
	"flag"
	"fmt"
	"maps"
	"os"
	"path/filepath"
	"slices"
	"sort"
	"text/template/parse"
)

var (
	titles  = make(map[string]struct{})
	configs = map[string]int{"Wikipedia": 1}
)

func usage() {
	fmt.Fprintf(os.Stderr, "Usage: %s [flags] template...\n",
		filepath.Base(os.Args[0]))
	flag.PrintDefaults()
}

func main() {
	try(os.Chdir(filepath.Dir(os.Args[0])))

	outpath := flag.String("out", "-", "output file")
	flag.Usage = usage
	flag.Parse()

	if flag.NArg() < 1 {
		flag.Usage()
		os.Exit(1)
	}

	var outfile *os.File
	if *outpath == "-" {
		outfile = os.Stdout
	} else {
		outfile = try2(os.Create(*outpath))
	}

	for _, f := range flag.Args() {
		process(f)
	}

	fmt.Fprint(outfile, `// Code generated by extwiki.  DO NOT EDIT.

package wikipedia

var extractedTitles = [...]string{
`)
	xs := slices.Collect(maps.Keys(titles))
	sort.Strings(xs)
	for _, t := range xs {
		fmt.Fprintf(outfile, "%q,\n", t)
	}
	fmt.Fprint(outfile, "}\n")
}

func process(path string) {
	currentFile := try2(os.ReadFile(path))
	trees := make(map[string]*parse.Tree)
	t := parse.New(path)
	t.Mode |= parse.ParseComments | parse.SkipFuncCheck
	try2(t.Parse(string(currentFile), "", "", trees))
	for _, t := range trees {
		processNode(t.Root)
	}
}

func processNode(node parse.Node) {
	switch n := node.(type) {
	case *parse.ListNode:
		for _, m := range n.Nodes {
			processNode(m)
		}
	case *parse.PipeNode:
		for _, m := range n.Cmds {
			processNode(m)
		}
	case *parse.TemplateNode:
		processNode(n.Pipe)
	case *parse.IfNode:
		processBranch(n.BranchNode)
	case *parse.RangeNode:
		processBranch(n.BranchNode)
	case *parse.WithNode:
		processBranch(n.BranchNode)
	case *parse.BranchNode:
		processBranch(*n)
	case *parse.ActionNode:
		processNode(n.Pipe)
	case *parse.CommandNode:
		if len(n.Args) == 0 {
			break
		}

		var funcname string
		f, ok := n.Args[0].(*parse.FieldNode)
		if !ok || len(f.Ident) == 0 {
			ff, ok := n.Args[0].(*parse.VariableNode)
			if !ok || len(ff.Ident) == 0 {
				fff, ok := n.Args[0].(*parse.IdentifierNode)
				if !ok {
					for _, pipe := range n.Args {
						processNode(pipe)
					}
					break
				}
				funcname = fff.Ident
			} else {
				funcname = ff.Ident[len(ff.Ident)-1]
			}
		} else {
			funcname = f.Ident[len(f.Ident)-1]
		}

		i, ok := configs[funcname]
		if !ok {
			for _, pipe := range n.Args {
				processNode(pipe)
			}
			break
		}

		if sn, ok := n.Args[i].(*parse.StringNode); ok {
			titles[sn.Text] = struct{}{}
		}
	}
}

func processBranch(n parse.BranchNode) {
	processNode(n.List)
	if n.ElseList != nil {
		processNode(n.ElseList)
	}
}

func try(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "%s: %s\n", filepath.Base(os.Args[0]), err)
		os.Exit(1)
	}
}

func try2[T any](val T, err error) T {
	try(err)
	return val
}