package api

import (
	"encoding/json"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"strings"
)

// RewriteServerInfoAddressables rewrites AddressablesCatalogUrlRoot values so
// clients fetch resources from publicBaseURL while leaving business API URLs
// untouched.
func RewriteServerInfoAddressables(raw []byte, publicBaseURL string) ([]byte, error) {
	var doc map[string]any
	if err := json.Unmarshal(raw, &doc); err != nil {
		return nil, fmt.Errorf("parse server-info: %w", err)
	}
	groups, _ := doc["ConnectionGroups"].([]any)
	for _, g := range groups {
		group, ok := g.(map[string]any)
		if !ok {
			continue
		}
		rewriteGroupAddressables(group, publicBaseURL)
		if overrides, ok := group["OverrideConnectionGroups"].([]any); ok {
			for _, o := range overrides {
				if og, ok := o.(map[string]any); ok {
					rewriteGroupAddressables(og, publicBaseURL)
				}
			}
		}
	}
	return json.Marshal(doc)
}

func rewriteGroupAddressables(group map[string]any, publicBaseURL string) {
	raw, _ := group["AddressablesCatalogUrlRoot"].(string)
	if raw == "" {
		return
	}
	if rewritten, ok := rewriteAddressablesRoot(raw, publicBaseURL); ok {
		group["AddressablesCatalogUrlRoot"] = rewritten
	}
}

func rewriteAddressablesRoot(original, publicBaseURL string) (string, bool) {
	original = strings.TrimRight(original, "/")
	publicBaseURL = strings.TrimRight(publicBaseURL, "/")
	// Already rewritten to this base.
	if strings.HasPrefix(original, publicBaseURL+"/"+ClientPatchHost) ||
		strings.HasPrefix(original, publicBaseURL+"/"+ServerInfoHost) {
		return original, true
	}
	u, err := url.Parse(original)
	if err != nil || u.Host == "" {
		return "", false
	}
	// Keep host/path so CDN path mapping stays 1:1 with destination_for_url.
	path := strings.TrimPrefix(u.Path, "/")
	if path == "" {
		return publicBaseURL + "/" + u.Host, true
	}
	return publicBaseURL + "/" + u.Host + "/" + path, true
}

// LoadServerInfoBytes loads server-info from an explicit file, or from the
// release tree under yostar-serverinfo host, or synthesizes a minimal document
// from the release snapshot addressables root.
func LoadServerInfoBytes(cfg Config, idx *ReleaseIndex, requestName string) ([]byte, error) {
	if cfg.ServerInfoFile != "" {
		return os.ReadFile(cfg.ServerInfoFile)
	}
	if idx != nil && idx.ResourceRoot != "" {
		name := requestName
		if name == "" {
			name = "server-info.json"
		}
		// Official path layout.
		candidates := []string{
			filepath.Join(idx.ResourceRoot, ServerInfoHost, name),
			filepath.Join(idx.ResourceRoot, ServerInfoHost, requestName),
		}
		for _, c := range candidates {
			if c == "" {
				continue
			}
			if data, err := os.ReadFile(c); err == nil {
				return data, nil
			}
		}
		// Any single json under server-info host.
		dir := filepath.Join(idx.ResourceRoot, ServerInfoHost)
		if entries, err := os.ReadDir(dir); err == nil {
			for _, e := range entries {
				if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") {
					continue
				}
				return os.ReadFile(filepath.Join(dir, e.Name()))
			}
		}
	}
	if idx != nil && idx.Snapshot != nil && idx.Snapshot.AddressablesRoot != "" {
		doc := map[string]any{
			"ConnectionGroups": []any{
				map[string]any{
					"Name":                       defaultString(idx.Snapshot.ConnectionGroupName, "Prod"),
					"AddressablesCatalogUrlRoot": idx.Snapshot.AddressablesRoot,
					"BundleVersion":              idx.Snapshot.BundleVersion,
					"IsLivePublished":            true,
				},
			},
		}
		return json.Marshal(doc)
	}
	return nil, fmt.Errorf("server-info source not found")
}

func defaultString(v, fallback string) string {
	if v == "" {
		return fallback
	}
	return v
}