package engine

import (
	"bytes"
	"fmt"
	"reflect"
	"strings"
	"text/template"

	"aiaa-notification-service/internal/display"
)

type Renderer struct{}

func NewRenderer() *Renderer {
	return &Renderer{}
}

func (r *Renderer) Render(tmplContent string, data map[string]interface{}) (string, error) {
	tmpl, err := template.New("notify").
		Option("missingkey=zero").
		Funcs(template.FuncMap{
			"line":    templateLine,
			"case":    templateCase,
			"replace": strings.ReplaceAll,
		}).
		Parse(tmplContent)
	if err != nil {
		return "", fmt.Errorf("parse template: %w", err)
	}
	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, display.WrapMap(data)); err != nil {
		return "", fmt.Errorf("execute template: %w", err)
	}
	return buf.String(), nil
}

// templateLine renders "label：value\n" or empty if value is missing/zero.
func templateLine(label string, v any) string {
	if isEmptyValue(v) {
		return ""
	}
	return strings.TrimRight(label, ":：") + "：" + fmt.Sprint(v) + "\n"
}

func templateCase(value any, pairs ...any) string {
	got := stringify(value)
	n := len(pairs)
	def := got
	if n%2 == 1 {
		def = stringify(pairs[n-1])
		pairs = pairs[:n-1]
	}
	for i := 0; i+1 < len(pairs); i += 2 {
		if caseKeyMatch(got, stringify(pairs[i])) {
			return stringify(pairs[i+1])
		}
	}
	return def
}

func caseKeyMatch(value, key string) bool {
	v := strings.ToLower(strings.TrimSpace(value))
	k := strings.ToLower(strings.TrimSpace(key))
	k = strings.TrimPrefix(k, ".")
	vSeg := v
	if i := strings.LastIndex(v, "."); i >= 0 {
		vSeg = v[i+1:]
	}
	return k == v || k == strings.TrimPrefix(v, ".") || k == vSeg
}

func stringify(v any) string {
	if v == nil {
		return ""
	}
	return fmt.Sprint(v)
}

func isEmptyValue(v any) bool {
	switch t := v.(type) {
	case nil:
		return true
	case string:
		return strings.TrimSpace(t) == ""
	case bool:
		return !t
	default:
		rv := reflect.ValueOf(v)
		switch rv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			return rv.Int() == 0
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			return rv.Uint() == 0
		case reflect.Float32, reflect.Float64:
			return rv.Float() == 0
		default:
			return false
		}
	}
}