package app

import (
	"encoding/json"
	"os"
	"strings"
)

func resolveAutoloopLocationSpec(locFile, defaultLoc string) autoloopLocationSpec {
	raw := ""
	if data, err := os.ReadFile(locFile); err == nil {
		for _, ln := range strings.Split(string(data), "\n") {
			t := strings.TrimSpace(ln)
			if t != "" && !strings.HasPrefix(t, "#") {
				raw = t
				break
			}
		}
	}
	if raw == "" {
		raw = strings.TrimSpace(defaultLoc)
	}
	raw = strings.TrimSpace(raw)
	primary := raw
	iso := ""
	if p := strings.SplitN(raw, "|", 2); len(p) == 2 {
		primary = strings.TrimSpace(p[0])
		iso = strings.ToUpper(strings.TrimSpace(p[1]))
	}
	if primary == "" {
		primary = strings.TrimSpace(defaultLoc)
	}
	if isISO2(primary) {
		iso = strings.ToUpper(primary)
	}
	if iso == "" {
		if tokens := strings.Fields(primary); len(tokens) > 0 && isISO2(tokens[0]) {
			iso = strings.ToUpper(tokens[0])
		}
	}
	if iso == "" {
		iso = lookupISOFromLocationsCache(primary)
	}
	if iso == "" && isISO2(defaultLoc) {
		iso = strings.ToUpper(strings.TrimSpace(defaultLoc))
	}
	return autoloopLocationSpec{
		Primary: primary,
		ISO:     iso,
	}
}

func isISO2(v string) bool {
	s := strings.TrimSpace(v)
	if len(s) != 2 {
		return false
	}
	for _, ch := range s {
		if (ch < 'A' || ch > 'Z') && (ch < 'a' || ch > 'z') {
			return false
		}
	}
	return true
}

func lookupISOFromLocationsCache(primary string) string {
	want := strings.ToLower(strings.TrimSpace(primary))
	if want == "" {
		return ""
	}

	var disk struct {
		Locations []struct {
			ISO    string `json:"iso"`
			Label  string `json:"label"`
			Target string `json:"target"`
		} `json:"locations"`
	}
	data, err := os.ReadFile(vpnLocationsCachePath)
	if err != nil {
		return ""
	}
	if err := json.Unmarshal(data, &disk); err != nil {
		return ""
	}

	for _, it := range disk.Locations {
		iso := strings.ToUpper(strings.TrimSpace(it.ISO))
		if !isISO2(iso) {
			continue
		}
		target := strings.ToLower(strings.TrimSpace(it.Target))
		if target != "" && target == want {
			return iso
		}
		labelNorm := strings.ToLower(strings.TrimSpace(it.Label))
		if labelNorm != "" {
			if inferVPNLocationTargetFromLabel(it.Label, iso) == primary {
				return iso
			}
			if strings.Contains(labelNorm, want) {
				return iso
			}
		}
	}
	return ""
}