package protocol

import (
	_ "embed"
	"encoding/json"
	"fmt"
	"strings"
)

const (
	DeepSeekHost                 = "chat.deepseek.com"
	DeepSeekLoginURL             = "https://chat.deepseek.com/api/v0/users/login"
	DeepSeekCreateSessionURL     = "https://chat.deepseek.com/api/v0/chat_session/create"
	DeepSeekCreatePowURL         = "https://chat.deepseek.com/api/v0/chat/create_pow_challenge"
	DeepSeekCompletionURL        = "https://chat.deepseek.com/api/v0/chat/completion"
	DeepSeekContinueURL          = "https://chat.deepseek.com/api/v0/chat/continue"
	DeepSeekUploadFileURL        = "https://chat.deepseek.com/api/v0/file/upload_file"
	DeepSeekFetchFilesURL        = "https://chat.deepseek.com/api/v0/file/fetch_files"
	DeepSeekFetchSessionURL      = "https://chat.deepseek.com/api/v0/chat_session/fetch_page"
	DeepSeekDeleteSessionURL     = "https://chat.deepseek.com/api/v0/chat_session/delete"
	DeepSeekDeleteAllSessionsURL = "https://chat.deepseek.com/api/v0/chat_session/delete_all"
	DeepSeekCompletionTargetPath = "/api/v0/chat/completion"
	DeepSeekUploadTargetPath     = "/api/v0/file/upload_file"
)

var defaultStaticBaseHeaders = map[string]string{
	"Host":           "chat.deepseek.com",
	"Accept":         "application/json",
	"Content-Type":   "application/json",
	"accept-charset": "UTF-8",
}

var defaultSkipContainsPatterns = []string{
	"quasi_status",
	"elapsed_secs",
	"token_usage",
	"pending_fragment",
	"conversation_mode",
	"fragments/-1/status",
	"fragments/-2/status",
	"fragments/-3/status",
}

var defaultSkipExactPaths = []string{
	"response/search_status",
}

var ClientVersion string
var currentPlatform = "android"
var currentAndroidAPILevel = "35" // default from normalizeClientConstants
var BaseHeaders = map[string]string{}
var SkipContainsPatterns = cloneStringSlice(defaultSkipContainsPatterns)
var SkipExactPathSet = toStringSet(defaultSkipExactPaths)

type clientConstants struct {
	Name            string `json:"name"`
	Platform        string `json:"platform"`
	Version         string `json:"version"`
	AndroidAPILevel string `json:"android_api_level"`
	Locale          string `json:"locale"`
}

type sharedConstants struct {
	Client              clientConstants   `json:"client"`
	BaseHeaders         map[string]string `json:"base_headers"`
	SkipContainsPattern []string          `json:"skip_contains_patterns"`
	SkipExactPaths      []string          `json:"skip_exact_paths"`
}

//go:embed constants_shared.json
var sharedConstantsJSON []byte

//go:embed constants_web.json
var webConstantsJSON []byte

func init() {
	cfg := sharedConstants{}
	if err := json.Unmarshal(sharedConstantsJSON, &cfg); err != nil {
		panic(fmt.Errorf("load DeepSeek shared constants: %w", err))
	}
	applySharedConstants(cfg)
}

func applySharedConstants(cfg sharedConstants) {
	client := normalizeClientConstants(cfg.Client)
	ClientVersion = client.Version
	if client.Platform == "android" {
		currentAndroidAPILevel = client.AndroidAPILevel
	}
	BaseHeaders = buildBaseHeaders(client, cfg.BaseHeaders)
	SkipContainsPatterns = cloneStringSlice(defaultSkipContainsPatterns)
	if len(cfg.SkipContainsPattern) > 0 {
		SkipContainsPatterns = cloneStringSlice(cfg.SkipContainsPattern)
	}
	SkipExactPathSet = toStringSet(defaultSkipExactPaths)
	if len(cfg.SkipExactPaths) > 0 {
		SkipExactPathSet = toStringSet(cfg.SkipExactPaths)
	}
}

func normalizeClientConstants(in clientConstants) clientConstants {
	if in.Name == "" {
		in.Name = "DeepSeek"
	}
	if in.Platform == "" {
		in.Platform = "android"
	}
	if in.AndroidAPILevel == "" {
		in.AndroidAPILevel = "35"
	}
	if in.Locale == "" {
		in.Locale = "zh_CN"
	}
	return in
}

func buildBaseHeaders(client clientConstants, overrides map[string]string) map[string]string {
	out := cloneStringMap(defaultStaticBaseHeaders)
	for k, v := range overrides {
		if k == "" || v == "" {
			continue
		}
		out[k] = v
	}
	out["User-Agent"] = userAgentForPlatform(client)
	if client.Platform != "" {
		out["x-client-platform"] = client.Platform
	}
	if client.Version != "" {
		out["x-client-version"] = client.Version
	}
	if client.Locale != "" {
		out["x-client-locale"] = client.Locale
	}
	return out
}

const webUserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36"

func userAgentForPlatform(client clientConstants) string {
	if client.Platform == "web" {
		return webUserAgent
	}
	if client.Name != "" && client.Version != "" {
		ua := client.Name + "/" + client.Version
		if client.Platform == "android" && client.AndroidAPILevel != "" {
			ua += " Android/" + client.AndroidAPILevel
		}
		return ua
	}
	return ""
}

// ApplyPlatform reloads constants for the given platform ("android" or "web").
func ApplyPlatform(platform string) {
	p := strings.ToLower(platform)
	var data []byte
	switch p {
	case "web":
		data = webConstantsJSON
	default:
		data = sharedConstantsJSON
		p = "android"
	}
	cfg := sharedConstants{}
	if err := json.Unmarshal(data, &cfg); err != nil {
		panic(fmt.Errorf("load DeepSeek %s constants: %w", p, err))
	}
	currentPlatform = p
	applySharedConstants(cfg)
}

// ApplyVersionOverrides patches ClientVersion and BaseHeaders with
// user-specified version overrides from config. Empty strings mean
// "keep the JSON default".
func ApplyVersionOverrides(androidVersion, webVersion, androidAPILevel string) {
	if currentPlatform == "android" {
		ver := androidVersion
		if ver == "" {
			ver = ClientVersion
		}
		apiLevel := androidAPILevel
		if apiLevel == "" {
			apiLevel = currentAndroidAPILevel
		}
		ClientVersion = ver
		BaseHeaders["x-client-version"] = ver
		BaseHeaders["x-client-platform"] = "android"
		BaseHeaders["User-Agent"] = "DeepSeek/" + ver + " Android/" + apiLevel
	} else if currentPlatform == "web" {
		ver := webVersion
		if ver == "" {
			ver = ClientVersion
		}
		ClientVersion = ver
		BaseHeaders["x-client-version"] = ver
		BaseHeaders["x-app-version"] = ver
	}
}

// IsWebPlatform returns whether the current platform is web.
func IsWebPlatform() bool {
	return currentPlatform == "web"
}

// UserAgent returns the appropriate User-Agent string based on the current platform.
func UserAgent() string {
	if currentPlatform == "web" {
		return webUserAgent
	}
	return "DeepSeek/" + ClientVersion
}

// WebExtraHeaders returns browser-specific headers that are not in the JSON
// config but need to be added dynamically for the web platform.
func WebExtraHeaders() map[string]string {
	return map[string]string{
		"sec-ch-ua":          `"Chromium";v="137", "Not/A)Brand";v="24"`,
		"sec-ch-ua-mobile":   "?0",
		"sec-ch-ua-platform": `"Windows"`,
		"origin":             "https://chat.deepseek.com",
		"referer":            "https://chat.deepseek.com/",
		"sec-fetch-dest":     "empty",
		"sec-fetch-mode":     "cors",
		"sec-fetch-site":     "same-origin",
	}
}

func cloneStringMap(in map[string]string) map[string]string {
	out := make(map[string]string, len(in))
	for k, v := range in {
		out[k] = v
	}
	return out
}

func cloneStringSlice(in []string) []string {
	out := make([]string, len(in))
	copy(out, in)
	return out
}

func toStringSet(in []string) map[string]struct{} {
	out := make(map[string]struct{}, len(in))
	for _, v := range in {
		if v == "" {
			continue
		}
		out[v] = struct{}{}
	}
	return out
}

const (
	KeepAliveTimeout  = 5
	StreamIdleTimeout = 300
	MaxKeepaliveCount = 40
)