package tmpl

import (
	"html/template"
	"io/fs"
	"path/filepath"
	"strings"
	txttmpl "text/template"
	"unicode/utf8"
)

// Templates for getting a template tree
type Templates struct {
	Suffix string
	Root   string
	Funcs  map[string]interface{}
	fs.FS
}

// HTML returns templates based on a filesystem
func (t Templates) HTML(name string) (*template.Template, error) {
	var ret *template.Template
	parseTemplates := func(name string, body []byte) error {
		var tmpl *template.Template
		if ret == nil {
			tmpl = template.New(name)
			if t.Funcs != nil {
				tmpl = tmpl.Funcs(template.FuncMap(t.Funcs))
			}
		} else {
			tmpl = ret.New(name)
		}
		tmpl, err := tmpl.Parse(string(body))
		if err != nil {
			return err
		}
		ret = tmpl
		return nil
	}
	if err := t.walk(parseTemplates); err != nil {
		return nil, err
	}
	if t := ret.Lookup(name); t != nil {
		return t, nil
	}
	return ret, nil
}

// Text returns templates based on a filesystem
func (t Templates) Text(name string) (*txttmpl.Template, error) {
	var ret *txttmpl.Template
	parseTemplates := func(name string, body []byte) error {
		var tmpl *txttmpl.Template
		if ret == nil {
			tmpl = txttmpl.New(name)
			if t.Funcs != nil {
				tmpl = tmpl.Funcs(txttmpl.FuncMap(t.Funcs))
			}
		} else {
			tmpl = ret.New(name)
		}
		tmpl, err := tmpl.Parse(string(body))
		if err != nil {
			return err
		}
		ret = tmpl
		return nil
	}

	if err := t.walk(parseTemplates); err != nil {
		return nil, err
	}
	if t := ret.Lookup(name); t != nil {
		return t, nil
	}
	return ret, nil
}

// List returns a list of files
func (t Templates) List() ([]string, error) {
	ret := []string{}
	err := t.walk(func(name string, _ []byte) error {
		ret = append(ret, name)
		return nil
	})
	if err != nil {
		return nil, err
	}
	return ret, nil
}

func (t Templates) walk(handle func(string, []byte) error) error {
	return fs.WalkDir(t.FS, t.getRoot(), func(path string, d fs.DirEntry, er error) (err error) {
		if er != nil {
			return er
		}
		if d.IsDir() {
			return nil
		}
		if !strings.HasSuffix(path, t.Suffix) {
			return nil
		}
		body, err := fs.ReadFile(t, path)
		if err != nil {
			return err
		}
		if !utf8.Valid(body) {
			return nil
		}
		return handle(t.trim(path), body)
	})
}

func (t Templates) getRoot() string {
	if t.Root == "" {
		return "."
	}
	return filepath.Clean(t.Root)
}

func (t Templates) trim(path string) string {
	cleaned := strings.TrimPrefix(filepath.Clean(path), filepath.Clean(t.Root))
	cleaned = strings.TrimPrefix(cleaned, "/")
	cleaned = strings.TrimSuffix(cleaned, t.Suffix)
	return strings.TrimSuffix(cleaned, ".")
}