package api

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"regexp"
	"strings"

	"github.com/sipeed/picoclaw/pkg/config"
	"github.com/sipeed/picoclaw/pkg/logger"
)

// registerConfigRoutes binds configuration management endpoints to the ServeMux.
func (h *Handler) registerConfigRoutes(mux *http.ServeMux) {
	mux.HandleFunc("GET /api/config", h.handleGetConfig)
	mux.HandleFunc("PUT /api/config", h.handleUpdateConfig)
	mux.HandleFunc("PATCH /api/config", h.handlePatchConfig)
	mux.HandleFunc("POST /api/config/test-command-patterns", h.handleTestCommandPatterns)
}

func (h *Handler) applyRuntimeLogLevel() {
	if h.debug {
		logger.SetLevel(logger.DEBUG)
		return
	}
	logger.SetLevelFromString(config.ResolveGatewayLogLevel(h.configPath))
}

// handleGetConfig returns the complete system configuration.
//
//	GET /api/config
func (h *Handler) handleGetConfig(w http.ResponseWriter, r *http.Request) {
	cfg, err := config.LoadConfig(h.configPath)
	if err != nil {
		http.Error(w, fmt.Sprintf("Failed to load config: %v", err), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(cfg); err != nil {
		http.Error(w, "Failed to encode response", http.StatusInternalServerError)
	}
}

// handleUpdateConfig updates the complete system configuration.
//
//	PUT /api/config
func (h *Handler) handleUpdateConfig(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
	if err != nil {
		http.Error(w, "Failed to read request body", http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	var cfg config.Config
	if err = json.Unmarshal(body, &cfg); err != nil {
		http.Error(w, fmt.Sprintf("Invalid JSON: %v", err), http.StatusBadRequest)
		return
	}
	var raw map[string]any
	if err = json.Unmarshal(body, &raw); err != nil {
		http.Error(w, fmt.Sprintf("Invalid JSON: %v", err), http.StatusBadRequest)
		return
	}
	if execAllowRemoteOmitted(body) {
		cfg.Tools.Exec.AllowRemote = config.DefaultConfig().Tools.Exec.AllowRemote
	}

	// Load existing config and copy security credentials before validation,
	// so that security-managed fields (e.g. pico token) are available.
	err = cfg.SecurityCopyFrom(h.configPath)
	if err != nil {
		http.Error(w, fmt.Sprintf("Failed to apply security config: %v", err), http.StatusInternalServerError)
		return
	}
	applyConfigSecretsFromMap(&cfg, raw)

	if errs := validateConfig(&cfg); len(errs) > 0 {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusBadRequest)
		json.NewEncoder(w).Encode(map[string]any{
			"status": "validation_error",
			"errors": errs,
		})
		return
	}

	if err := config.SaveConfig(h.configPath, &cfg); err != nil {
		http.Error(w, fmt.Sprintf("Failed to save config: %v", err), http.StatusInternalServerError)
		return
	}

	// Refresh cached pico token in case user changed it.
	refreshPicoToken(&cfg)
	h.applyRuntimeLogLevel()
	logger.Infof("configuration updated successfully")

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
}

func execAllowRemoteOmitted(body []byte) bool {
	var raw struct {
		Tools *struct {
			Exec *struct {
				AllowRemote *bool `json:"allow_remote"`
			} `json:"exec"`
		} `json:"tools"`
	}
	if err := json.Unmarshal(body, &raw); err != nil {
		return false
	}
	return raw.Tools == nil || raw.Tools.Exec == nil || raw.Tools.Exec.AllowRemote == nil
}

// handlePatchConfig partially updates the system configuration using JSON Merge Patch (RFC 7396).
// Only the fields present in the request body will be updated; all other fields remain unchanged.
//
//	PATCH /api/config
func (h *Handler) handlePatchConfig(w http.ResponseWriter, r *http.Request) {
	patchBody, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
	if err != nil {
		http.Error(w, "Failed to read request body", http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	// Validate the patch is valid JSON
	var patch map[string]any
	if err = json.Unmarshal(patchBody, &patch); err != nil {
		http.Error(w, fmt.Sprintf("Invalid JSON: %v", err), http.StatusBadRequest)
		return
	}

	// Load existing config and marshal to a map for merging
	cfg, err := config.LoadConfig(h.configPath)
	if err != nil {
		http.Error(w, fmt.Sprintf("Failed to load config: %v", err), http.StatusInternalServerError)
		return
	}
	existing, err := json.Marshal(cfg)
	if err != nil {
		http.Error(w, "Failed to serialize current config", http.StatusInternalServerError)
		return
	}

	var base map[string]any
	if err = json.Unmarshal(existing, &base); err != nil {
		http.Error(w, "Failed to parse current config", http.StatusInternalServerError)
		return
	}

	// Recursively merge patch into base
	mergeMap(base, patch)

	// Convert merged map back to Config struct
	merged, err := json.Marshal(base)
	if err != nil {
		http.Error(w, "Failed to serialize merged config", http.StatusInternalServerError)
		return
	}

	var newCfg config.Config
	if err = json.Unmarshal(merged, &newCfg); err != nil {
		http.Error(w, fmt.Sprintf("Merged config is invalid: %v", err), http.StatusBadRequest)
		return
	}

	// Restore security fields (tokens/keys) from the loaded config before validation,
	// because private fields are lost during JSON round-trip.
	if err = newCfg.SecurityCopyFrom(h.configPath); err != nil {
		http.Error(w, fmt.Sprintf("Failed to apply security config: %v", err), http.StatusInternalServerError)
		return
	}
	applyConfigSecretsFromMap(&newCfg, base)

	if errs := validateConfig(&newCfg); len(errs) > 0 {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusBadRequest)
		json.NewEncoder(w).Encode(map[string]any{
			"status": "validation_error",
			"errors": errs,
		})
		return
	}

	if err := config.SaveConfig(h.configPath, &newCfg); err != nil {
		http.Error(w, fmt.Sprintf("Failed to save config: %v", err), http.StatusInternalServerError)
		return
	}

	// Refresh cached pico token in case user changed it.
	refreshPicoToken(&newCfg)
	h.applyRuntimeLogLevel()
	logger.Infof("configuration updated successfully")

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
}

// handleTestCommandPatterns tests a command against whitelist and blacklist patterns.
//
//	POST /api/config/test-command-patterns
func (h *Handler) handleTestCommandPatterns(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
	if err != nil {
		http.Error(w, "Failed to read request body", http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	var req struct {
		AllowPatterns []string `json:"allow_patterns"`
		DenyPatterns  []string `json:"deny_patterns"`
		Command       string   `json:"command"`
	}
	if err := json.Unmarshal(body, &req); err != nil {
		http.Error(w, fmt.Sprintf("Invalid JSON: %v", err), http.StatusBadRequest)
		return
	}

	lower := strings.ToLower(strings.TrimSpace(req.Command))

	type result struct {
		Allowed          bool    `json:"allowed"`
		Blocked          bool    `json:"blocked"`
		MatchedWhitelist *string `json:"matched_whitelist,omitempty"`
		MatchedBlacklist *string `json:"matched_blacklist,omitempty"`
	}

	resp := result{Allowed: false, Blocked: false}

	// Check whitelist first
	for _, pattern := range req.AllowPatterns {
		re, err := regexp.Compile(pattern)
		if err != nil {
			continue // skip invalid patterns
		}
		if re.MatchString(lower) {
			resp.Allowed = true
			resp.MatchedWhitelist = &pattern
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(resp)
			return
		}
	}

	// Check blacklist
	for _, pattern := range req.DenyPatterns {
		re, err := regexp.Compile(pattern)
		if err != nil {
			continue
		}
		if re.MatchString(lower) {
			resp.Blocked = true
			resp.MatchedBlacklist = &pattern
			break
		}
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp)
}

// validateConfig checks the config for common errors before saving.
// Returns a list of human-readable error strings; empty means valid.
func validateConfig(cfg *config.Config) []string {
	var errs []string

	// Validate model_list entries
	if err := cfg.ValidateModelList(); err != nil {
		errs = append(errs, err.Error())
	}

	// Gateway port range
	if cfg.Gateway.Port != 0 && (cfg.Gateway.Port < 1 || cfg.Gateway.Port > 65535) {
		errs = append(errs, fmt.Sprintf("gateway.port %d is out of valid range (1-65535)", cfg.Gateway.Port))
	}

	// Pico channel: token required when enabled
	{
		bc := cfg.Channels.GetByType(config.ChannelPico)
		if bc != nil && bc.Enabled {
			if decoded, err := bc.GetDecoded(); err == nil && decoded != nil {
				if c, ok := decoded.(*config.PicoSettings); ok && c.Token.String() == "" {
					errs = append(errs, "channels.pico.token is required when pico channel is enabled")
				}
			}
		}
	}

	// Telegram: token required when enabled
	{
		bc := cfg.Channels.GetByType(config.ChannelTelegram)
		if bc != nil && bc.Enabled {
			if decoded, err := bc.GetDecoded(); err == nil && decoded != nil {
				if c, ok := decoded.(*config.TelegramSettings); ok && c.Token.String() == "" {
					errs = append(errs, "channels.telegram.token is required when telegram channel is enabled")
				}
			}
		}
	}

	// Discord: token required when enabled
	{
		bc := cfg.Channels.GetByType(config.ChannelDiscord)
		if bc != nil && bc.Enabled {
			if decoded, err := bc.GetDecoded(); err == nil && decoded != nil {
				if c, ok := decoded.(*config.DiscordSettings); ok && c.Token.String() == "" {
					errs = append(errs, "channels.discord.token is required when discord channel is enabled")
				}
			}
		}
	}

	{
		bc := cfg.Channels.GetByType(config.ChannelWeCom)
		if bc != nil && bc.Enabled {
			if decoded, err := bc.GetDecoded(); err == nil && decoded != nil {
				if c, ok := decoded.(*config.WeComSettings); ok {
					if c.BotID == "" {
						errs = append(errs, "channels.wecom.bot_id is required when wecom channel is enabled")
					}
					if c.Secret.String() == "" {
						errs = append(errs, "channels.wecom.secret is required when wecom channel is enabled")
					}
				}
			}
		}
	}

	if cfg.Tools.Exec.Enabled {
		if cfg.Tools.Exec.EnableDenyPatterns {
			errs = append(
				errs,
				validateRegexPatterns("tools.exec.custom_deny_patterns", cfg.Tools.Exec.CustomDenyPatterns)...)
		}
		errs = append(
			errs,
			validateRegexPatterns("tools.exec.custom_allow_patterns", cfg.Tools.Exec.CustomAllowPatterns)...)
	}

	return errs
}

func validateRegexPatterns(field string, patterns []string) []string {
	var errs []string
	for index, pattern := range patterns {
		if _, err := regexp.Compile(pattern); err != nil {
			errs = append(errs, fmt.Sprintf("%s[%d] is not a valid regular expression: %v", field, index, err))
		}
	}
	return errs
}

// mergeMap recursively merges src into dst (JSON Merge Patch semantics).
// - If a key in src has a null value, it is deleted from dst.
// - If both dst and src have a nested object for the same key, merge recursively.
// - Otherwise the value from src overwrites dst.
func mergeMap(dst, src map[string]any) {
	for key, srcVal := range src {
		if srcVal == nil {
			delete(dst, key)
			continue
		}
		srcMap, srcIsMap := srcVal.(map[string]any)
		dstMap, dstIsMap := dst[key].(map[string]any)
		if srcIsMap && dstIsMap {
			mergeMap(dstMap, srcMap)
		} else {
			dst[key] = srcVal
		}
	}
}

func asMapField(value map[string]any, key string) (map[string]any, bool) {
	raw, exists := value[key]
	if !exists {
		return nil, false
	}
	m, isMap := raw.(map[string]any)
	return m, isMap
}

func getSecretString(m map[string]any, key string) (string, bool) {
	if raw, exists := m[key]; exists {
		s, isString := raw.(string)
		if isString {
			return s, true
		}
	}
	if raw, exists := m["_"+key]; exists {
		s, isString := raw.(string)
		if isString {
			return s, true
		}
	}
	return "", false
}

func applyConfigSecretsFromMap(cfg *config.Config, raw map[string]any) {
	channelsMap, hasChannels := asMapField(raw, "channel_list")
	if !hasChannels {
		return
	}

	for chName, chData := range channelsMap {
		chMap, ok := chData.(map[string]any)
		if !ok {
			continue
		}
		bc := cfg.Channels.Get(chName)
		if bc == nil {
			continue
		}
		decoded, err := bc.GetDecoded()
		if err != nil || decoded == nil {
			continue
		}
		rv := reflect.ValueOf(decoded)
		if rv.Kind() == reflect.Ptr {
			rv = rv.Elem()
		}
		if rv.Kind() != reflect.Struct {
			continue
		}
		// Channel-specific settings live under the "settings" key in the raw map
		settingsMap := chMap
		if sm, hasSettings := asMapField(chMap, "settings"); hasSettings {
			settingsMap = sm
		}
		applySecureStringsToStruct(rv, settingsMap)
	}

	// Handle tools secrets
	tools, hasTools := asMapField(raw, "tools")
	if !hasTools {
		return
	}
	skills, hasSkills := asMapField(tools, "skills")
	if !hasSkills {
		return
	}
	if github, hasGithub := asMapField(skills, "github"); hasGithub {
		if token, hasToken := getSecretString(github, "token"); hasToken {
			cfg.Tools.Skills.Github.Token.Set(token)
		}
	}
	if registries, hasRegistries := asMapField(skills, "registries"); hasRegistries {
		for registryName, rawRegistry := range registries {
			registryMap, ok := rawRegistry.(map[string]any)
			if !ok {
				continue
			}
			if authToken, hasAuthToken := getSecretString(registryMap, "auth_token"); hasAuthToken {
				registryCfg, _ := cfg.Tools.Skills.Registries.Get(registryName)
				registryCfg.AuthToken.Set(authToken)
				cfg.Tools.Skills.Registries.Set(registryName, registryCfg)
			}
		}
		return
	}

	registriesList, hasRegistries := skills["registries"].([]any)
	if !hasRegistries {
		return
	}
	for _, rawRegistry := range registriesList {
		registryMap, ok := rawRegistry.(map[string]any)
		if !ok {
			continue
		}
		name, _ := registryMap["name"].(string)
		if name == "" {
			continue
		}
		if authToken, hasAuthToken := getSecretString(registryMap, "auth_token"); hasAuthToken {
			registryCfg, _ := cfg.Tools.Skills.Registries.Get(name)
			registryCfg.AuthToken.Set(authToken)
			cfg.Tools.Skills.Registries.Set(name, registryCfg)
		}
	}
}

// applySecureStringsToStruct walks a struct and applies SecureString fields
// from the matching keys in rawMap. It recurses into nested maps and slices.
func applySecureStringsToStruct(rv reflect.Value, rawMap map[string]any) {
	rt := rv.Type()
	for jsonKey, rawVal := range rawMap {
		for i := range rt.NumField() {
			f := rt.Field(i)
			if !f.IsExported() {
				continue
			}
			tag := f.Tag.Get("json")
			name := strings.Split(tag, ",")[0]
			if name != jsonKey {
				continue
			}
			sf := rv.Field(i)
			if !sf.CanSet() {
				continue
			}
			// Direct SecureString field
			if s, ok := rawVal.(string); ok {
				if f.Type == reflect.TypeOf(config.SecureString{}) {
					sf.Set(reflect.ValueOf(*config.NewSecureString(s)))
				} else if f.Type == reflect.TypeOf(&config.SecureString{}) {
					sf.Set(reflect.ValueOf(config.NewSecureString(s)))
				}
				continue
			}
			// Recurse into nested struct
			if sf.Kind() == reflect.Struct {
				if nested, ok := rawVal.(map[string]any); ok {
					applySecureStringsToStruct(sf, nested)
				}
				continue
			}
			// Recurse into map fields (e.g., map[string]SomeStruct)
			if sf.Kind() == reflect.Map && sf.Type().Elem().Kind() == reflect.Struct {
				if nestedMap, ok := rawVal.(map[string]any); ok {
					for mapKey, mapVal := range nestedMap {
						nested, ok := mapVal.(map[string]any)
						if !ok {
							continue
						}
						elemType := sf.Type().Elem()
						// Get existing element or create a new zero value
						var elem reflect.Value
						existing := sf.MapIndex(reflect.ValueOf(mapKey))
						if existing.IsValid() {
							if existing.Kind() == reflect.Interface {
								existing = existing.Elem()
							}
							if existing.Kind() == reflect.Ptr && !existing.IsNil() {
								elem = reflect.New(elemType)
								elem.Elem().Set(existing.Elem())
							} else if existing.Kind() == reflect.Struct {
								elem = reflect.New(elemType)
								elem.Elem().Set(existing)
							}
						}
						if !elem.IsValid() {
							elem = reflect.New(elemType)
						}
						applySecureStringsToStruct(elem.Elem(), nested)
						sf.SetMapIndex(reflect.ValueOf(mapKey), elem.Elem())
					}
				}
				continue
			}
			// Recurse into slice elements that are structs
			if sf.Kind() == reflect.Slice && sf.Type().Elem().Kind() == reflect.Struct {
				if sliceRaw, ok := rawVal.([]any); ok {
					for idx, elemRaw := range sliceRaw {
						if nested, ok := elemRaw.(map[string]any); ok {
							if idx < sf.Len() {
								applySecureStringsToStruct(sf.Index(idx), nested)
							}
						}
					}
				}
			}
		}
	}
}