// channels.go loads and persists the runtime-editable channel-adapter
// configuration: the per-platform account list in channels.json (design/04
// §3.1). The .env channel block (CHANNELS_JSON + CHANNEL_<PLATFORM>_*) is the
// final fallback; a present-and-valid channels.json takes precedence and is
// hot-reloaded at runtime without a restart.
//
// channels.json is gitignored (local runtime config) and holds bot tokens, so
// this package never logs a token and never exposes one un-masked to a caller
// that only wants a display snapshot (Masked).
package runtimeconfig

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
)

// channelsFileName is the channels.json basename stored under the data dir.
const channelsFileName = "channels.json"

// ErrInvalidChannels is returned when a channels.json fails schema validation.
var ErrInvalidChannels = errors.New("runtimeconfig: invalid channels config")

// tokenKeys are the config-map keys whose value is a secret and must never be
// emitted verbatim by Masked (or a log line). A key is treated as sensitive when
// its lower-cased form contains any of these substrings.
var tokenKeys = []string{"token", "secret", "password", "api_key", "apikey", "access_key", "key"}

// DefaultChannelsPath returns the channels.json path under dataDir.
func DefaultChannelsPath(dataDir string) string {
	return filepath.Join(dataDir, channelsFileName)
}

// LoadChannels returns the effective per-platform account map. When path is a
// present-and-valid channels.json it is authoritative; otherwise it falls back
// to envFallback (the .env/CHANNELS_JSON channel block computed by the caller).
// A present-but-invalid file falls back to env and returns a non-nil warning so
// the caller can log it. The returned map is non-nil. A file-loaded account list
// is cleaned (bare empty-token placeholders dropped) so a stale channels.json
// never surfaces an account that cannot connect; the caller's envFallback is
// left untouched.
func LoadChannels(path string, envFallback map[string][]config.ChannelAccount) (map[string][]config.ChannelAccount, error) {
	accounts, readErr := loadChannelsFile(path)
	if readErr == nil {
		return cleanAccounts(accounts), nil
	}
	var warn error
	if !os.IsNotExist(readErr) {
		warn = fmt.Errorf("runtimeconfig: %s: %w", path, readErr)
	}
	if envFallback == nil {
		envFallback = map[string][]config.ChannelAccount{}
	}
	return envFallback, warn
}

// loadChannelsFile decodes and validates the channels.json map. A nil/blank
// file, a JSON decode error or an empty map all return an error so the caller
// falls back to env — an empty config file should never silently wipe the
// channels that env still provides.
func loadChannelsFile(path string) (map[string][]config.ChannelAccount, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	if len(strings.TrimSpace(string(raw))) == 0 {
		return nil, fmt.Errorf("%w: empty file", ErrInvalidChannels)
	}
	accounts, err := config.ParseChannelAccounts(string(raw))
	if err != nil {
		return nil, fmt.Errorf("%w: %v", ErrInvalidChannels, err)
	}
	if len(accounts) == 0 {
		return nil, fmt.Errorf("%w: no accounts", ErrInvalidChannels)
	}
	return accounts, nil
}

// SaveChannels writes accounts as a pretty-printed JSON map to path with mode
// 0600 (the file holds bot tokens). It writes to a temp file then renames so a
// concurrent reader never sees a partial file. Bare empty-token placeholders are
// dropped before writing, so an unusable account never lands in the file.
func SaveChannels(path string, accounts map[string][]config.ChannelAccount) error {
	if accounts == nil {
		accounts = map[string][]config.ChannelAccount{}
	}
	accounts = cleanAccounts(accounts)
	dir := filepath.Dir(path)
	if dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return fmt.Errorf("runtimeconfig: mkdir: %w", err)
		}
	}
	raw, err := json.MarshalIndent(accounts, "", "  ")
	if err != nil {
		return fmt.Errorf("runtimeconfig: marshal: %w", err)
	}
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, raw, 0o600); err != nil {
		return fmt.Errorf("runtimeconfig: write %s: %w", tmp, err)
	}
	if err := os.Rename(tmp, path); err != nil {
		return fmt.Errorf("runtimeconfig: rename: %w", err)
	}
	return nil
}

// UpsertChannel returns accounts with acct inserted or replaced in place within
// its platform by ID, preserving order. A blank ID is assigned a generated id so
// a panel save without an explicit id still produces a stable, addressable account.
func UpsertChannel(accounts map[string][]config.ChannelAccount, platform string, acct config.ChannelAccount) map[string][]config.ChannelAccount {
	if accounts == nil {
		accounts = map[string][]config.ChannelAccount{}
	}
	if strings.TrimSpace(acct.ID) == "" {
		acct.ID = NewID()
	}
	list := accounts[platform]
	out := make([]config.ChannelAccount, 0, len(list)+1)
	replaced := false
	for _, cur := range list {
		if cur.ID == acct.ID {
			out = append(out, acct)
			replaced = true
			continue
		}
		out = append(out, cur)
	}
	if !replaced {
		out = append(out, acct)
	}
	accounts[platform] = out
	return accounts
}

// PatchChannel 以 **patch 语义** 写入一个账号，是 UpsertChannel 的补丁版：
// acct.Config 被当作「只含本次请求显式给出的键」的补丁，而不是一整套完整配置。
//
//   - 补丁里**缺位的键**   → 保留该账号已存值（未被触碰的键绝不因一次保存被抹掉）；
//   - 补丁里给出的非空值   → 覆盖该键；
//   - 补丁里给出 nil 或空白字符串 → **删除**该键（保留「清空」能力，删掉后适配器回落到自己的零值）。
//
// 同平台同 id 的已存条目是补丁的基线；没有基线时（新账号，或 id 为空、由 UpsertChannel
// 生成 id）只写入补丁本身。acct 的其它字段（黑白名单 / 限流 / personaId）与 UpsertChannel
// 一样是整值替换 —— 它们在线上是值语义，不是三态。返回值与入参 accounts 的关系同 UpsertChannel。
func PatchChannel(accounts map[string][]config.ChannelAccount, platform string, acct config.ChannelAccount) map[string][]config.ChannelAccount {
	if accounts == nil {
		accounts = map[string][]config.ChannelAccount{}
	}
	var stored config.ChannelAccount
	if id := strings.TrimSpace(acct.ID); id != "" {
		for _, cur := range accounts[platform] {
			if cur.ID == id {
				stored = cur
				break
			}
		}
	}
	acct.Config = mergeChannelConfig(stored.Config, acct.Config)
	return UpsertChannel(accounts, platform, acct)
}

// mergeChannelConfig 把补丁合并进已存 config，返回一个新 map（stored 与 patch 均不被改动）。
// 缺位的键保留已存值；nil/空白的补丁值删除该键；其余覆盖。空补丁是恒等变换。
func mergeChannelConfig(stored, patch map[string]any) map[string]any {
	out := make(map[string]any, len(stored)+len(patch))
	for k, v := range stored {
		out[k] = v
	}
	for k, v := range patch {
		if isEmptyConfigValue(v) {
			delete(out, k)
			continue
		}
		out[k] = v
	}
	return out
}

// isEmptyConfigValue 报告一个补丁值是否表示「清除该键」：显式 nil，或只含空白的字符串。
// 其它类型（数字/布尔/对象/数组）永远不算空 —— 0 与 false 是真实取值，不是「未设置」。
func isEmptyConfigValue(v any) bool {
	switch t := v.(type) {
	case nil:
		return true
	case string:
		return strings.TrimSpace(t) == ""
	default:
		return false
	}
}

// DeleteChannel returns accounts with the account of the given id removed from
// its platform. When the platform has no remaining accounts the platform key is
// dropped entirely, so a reload of that platform yields no adapters.
func DeleteChannel(accounts map[string][]config.ChannelAccount, platform, id string) map[string][]config.ChannelAccount {
	if accounts == nil {
		return map[string][]config.ChannelAccount{}
	}
	out := make([]config.ChannelAccount, 0, len(accounts[platform]))
	for _, cur := range accounts[platform] {
		if cur.ID == id {
			continue
		}
		out = append(out, cur)
	}
	if len(out) == 0 {
		delete(accounts, platform)
	} else {
		accounts[platform] = out
	}
	return accounts
}

// Masked returns a copy of acct whose Config has every secret value redacted,
// for display/logging. It never reveals more than the trailing 4 characters of a
// token, so a secret never lands verbatim in a wire response or a log line. The
// original account (and the channels.json on disk) is untouched.
func Masked(acct config.ChannelAccount) config.ChannelAccount {
	out := acct
	out.Config = maskConfig(acct.Config)
	return out
}

// maskConfig redacts the values of sensitive keys in a config map. If a sensitive
// value is not a string it is passed through unchanged (never a token).
func maskConfig(m map[string]any) map[string]any {
	if m == nil {
		return nil
	}
	out := make(map[string]any, len(m))
	for k, v := range m {
		if isSensitiveKey(k) {
			if s, ok := v.(string); ok {
				out[k] = maskToken(s)
				continue
			}
		}
		out[k] = v
	}
	return out
}

// isSensitiveKey reports whether a config key holds a secret. It matches the
// bot_token/access_token/secret/api_key family used across the adapters.
func isSensitiveKey(k string) bool {
	lk := strings.ToLower(k)
	for _, sub := range tokenKeys {
		if strings.Contains(lk, sub) {
			return true
		}
	}
	return false
}

// maskToken redacts a token to the trailing 4 characters (or all-asterisks when
// it is 4 characters or fewer).
func maskToken(s string) string {
	if len(s) <= 4 {
		return "****"
	}
	return "****" + s[len(s)-4:]
}

// tokenRequiringPlatforms are the adapters whose connection needs a bot token
// (design/08 §4). An account for one of these with an empty bot_token is a bare
// placeholder: it can never connect and must not claim the bare platform name
// (design/16 §4.5), so it is dropped from the effective config and from
// channels.json. Other platforms (qq-obv11, webhook) are left alone so their
// channel list stays stable while the bridge's configured() gate decides whether
// to dial.
//
// weixin-ilink is deliberately NOT token-required here: an empty-token account is
// a legitimate pending scan-login (design/08 §4). The panel saves a bare weixin
// account, drives get_bot_qrcode/get_qrcode_status via the admin login endpoints,
// and the bridge's configured() gate keeps it disconnected until the scan
// confirms and the token is persisted — so such an account must survive loading
// and writing, not be dropped as a placeholder.
func tokenRequiringPlatforms(platform string) bool {
	switch platform {
	case "kook", "telegram":
		return true
	default:
		return false
	}
}

// cleanAccounts drops unusable bare accounts from an accounts map. For a
// token-requiring platform any account with an empty bot_token is dropped (a
// bare "kook"/"telegram"/"weixin-ilink" placeholder can never connect). It never
// logs or returns a token.
func cleanAccounts(accounts map[string][]config.ChannelAccount) map[string][]config.ChannelAccount {
	if accounts == nil {
		return accounts
	}
	out := make(map[string][]config.ChannelAccount, len(accounts))
	for platform, list := range accounts {
		if !tokenRequiringPlatforms(platform) {
			out[platform] = list
			continue
		}
		kept := make([]config.ChannelAccount, 0, len(list))
		for _, a := range list {
			if strings.TrimSpace(accountBotToken(a)) == "" {
				continue
			}
			kept = append(kept, a)
		}
		if len(kept) > 0 {
			out[platform] = kept
		}
	}
	return out
}

// accountBotToken returns the account's bot_token value (the credential the
// token-requiring platforms need). It never logs the token.
func accountBotToken(a config.ChannelAccount) string {
	if s, ok := a.Config["bot_token"].(string); ok {
		return s
	}
	return ""
}

// AdminIDs 汇总 channels.json 里各账号声明的管理员 id（裁决 06.4.2；design/08 §1.1、
// design/11 §0），返回 platform → 去重后的管理员 id 列表（同一平台的多账号声明会合并去重、
// 空串被丢弃）。**结果覆盖 accounts 里的每个平台**：未声明 adminIds 的平台对应空切片，
// 这样 `for p, ids := range AdminIDs(accounts) { profile.SetPlatformAdmins(p, ids) }`
// 就是一次整体替换——热重载后删掉的管理员 id 会立即失效（不会有悬挂管理员）。返回的切片是
// 新建的，调用方改动它不影响 accounts。
func AdminIDs(accounts map[string][]config.ChannelAccount) map[string][]string {
	out := make(map[string][]string, len(accounts))
	for platform, list := range accounts {
		seen := make(map[string]struct{})
		var ids []string
		for _, acct := range list {
			for _, id := range acct.AdminIDs {
				trimmed := strings.TrimSpace(id)
				if trimmed == "" {
					continue
				}
				if _, dup := seen[trimmed]; dup {
					continue
				}
				seen[trimmed] = struct{}{}
				ids = append(ids, trimmed)
			}
		}
		out[platform] = ids
	}
	return out
}