// Package config 提供基于 viper 的应用配置加载，按 默认值 → 配置文件 → 环境变量 的优先级合并。
package config

import (
	"encoding/hex"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"github.com/spf13/viper"
)

// MasterKey wraps a 32-byte AES master key with redacted formatting to prevent
// accidental log/fmt exposure.
type MasterKey []byte

// String redacts when used with %s / fmt.Println.
func (k MasterKey) String() string { return "[REDACTED 32B]" }

// GoString redacts when used with %#v.
func (k MasterKey) GoString() string { return "[REDACTED 32B]" }

// MarshalJSON redacts when serialized to JSON.
func (k MasterKey) MarshalJSON() ([]byte, error) { return []byte(`"[REDACTED]"`), nil }

// LogValue redacts when logged via slog.
func (k MasterKey) LogValue() slog.Value { return slog.StringValue("[REDACTED 32B]") }

// Config 是应用全局配置的根结构。
type Config struct {
	Env       string          `mapstructure:"env"`
	DataDir   string          `mapstructure:"data_dir"`
	MasterKey MasterKey       `mapstructure:"-"` // 解码后的 32 字节，单独从 master_key 解析
	HTTP      HTTPConfig      `mapstructure:"http"`
	DB        DBConfig        `mapstructure:"db"`
	Bootstrap BootstrapConfig `mapstructure:"bootstrap"`
	Workspace Workspace       `mapstructure:"workspace"`
	Git       Git             `mapstructure:"git"`
	Chat      Chat            `mapstructure:"chat"`
	Storage   Storage         `mapstructure:"storage"`
	Jobs      JobsConfig      `mapstructure:"jobs"`
	Notify    NotifyConfig    `mapstructure:"notify"`
}

// HTTPConfig 描述 HTTP 服务监听参数。
type HTTPConfig struct {
	Addr string `mapstructure:"addr"`
}

// DBConfig 描述数据库连接参数。
type DBConfig struct {
	DSN string `mapstructure:"dsn"`
}

// BootstrapConfig 描述首次启动注入的管理员账号。
type BootstrapConfig struct {
	AdminEmail    string `mapstructure:"admin_email"`
	AdminPassword string `mapstructure:"admin_password"`
}

// Workspace 控制 workspace 模块的磁盘与超时（数据目录、每个 git verb 的超时）。
// DataDir 是 workspace clone/worktree 落盘根目录；五个 timeout 直接灌进 git.Config。
type Workspace struct {
	DataDir      string        `mapstructure:"data_dir"`
	CloneTimeout time.Duration `mapstructure:"clone_timeout"`
	FetchTimeout time.Duration `mapstructure:"fetch_timeout"`
	PushTimeout  time.Duration `mapstructure:"push_timeout"`
	OpsTimeout   time.Duration `mapstructure:"ops_timeout"`
}

// Git 控制 git CLI 二进制位置（默认 "git"）。
type Git struct {
	Binary string `mapstructure:"binary"`
}

// Chat 配置 chat 模块的附件、流式、历史与定时清理策略。
type Chat struct {
	Attachment ChatAttachment `mapstructure:"attachment"`
	Stream     ChatStream     `mapstructure:"stream"`
	History    ChatHistory    `mapstructure:"history"`
}

// ChatAttachment 控制单文件 / 单消息上限与允许的 MIME 白名单。
type ChatAttachment struct {
	MaxFileSizeMB    int64    `mapstructure:"max_file_size_mb"`
	MaxMessageSizeMB int64    `mapstructure:"max_message_size_mb"`
	MimeWhitelist    []string `mapstructure:"mime_whitelist"`
}

// ChatStream 控制 SSE ring buffer 保留时长与取消宽限期。
type ChatStream struct {
	RingBufferRetentionSeconds int `mapstructure:"ring_buffer_retention_seconds"`
}

// ChatHistory 控制 token 预算的安全余量百分比（如 5 表示保留 5% 余量）。
type ChatHistory struct {
	SafetyMarginPct float64 `mapstructure:"safety_margin_pct"`
}

// Storage 选择附件落盘驱动与对应参数。
type Storage struct {
	Driver  string         `mapstructure:"driver"` // 当前仅支持 "localfs"
	LocalFS StorageLocalFS `mapstructure:"localfs"`
}

// StorageLocalFS 是 driver=localfs 时的根目录。
type StorageLocalFS struct {
	BasePath string `mapstructure:"base_path"`
}

// JobsConfig 控制后台 job runner 的总开关、worker 池与各定时任务参数。
type JobsConfig struct {
	Enabled           bool                 `mapstructure:"enabled"`
	Workers           int                  `mapstructure:"workers"`
	ShutdownGrace     time.Duration        `mapstructure:"shutdown_grace"`
	WorkspaceFetch    RunnerCfg            `mapstructure:"workspace_fetch"`
	WorktreePrune     WorktreePruneCfg     `mapstructure:"worktree_prune"`
	AttachmentCleanup AttachmentCleanupCfg `mapstructure:"attachment_cleanup"`
	JobReaper         JobReaperCfg         `mapstructure:"job_reaper"`
	JobPurge          JobPurgeCfg          `mapstructure:"job_purge"`
}

type RunnerCfg struct {
	Enabled  bool          `mapstructure:"enabled"`
	Interval time.Duration `mapstructure:"interval"`
}

type WorktreePruneCfg struct {
	Enabled       bool          `mapstructure:"enabled"`
	Interval      time.Duration `mapstructure:"interval"`
	IdleThreshold time.Duration `mapstructure:"idle_threshold"`
	WarningLead   time.Duration `mapstructure:"warning_lead"`
}

type AttachmentCleanupCfg struct {
	Enabled   bool          `mapstructure:"enabled"`
	Interval  time.Duration `mapstructure:"interval"`
	Retention time.Duration `mapstructure:"retention"`
}

type JobReaperCfg struct {
	Enabled      bool          `mapstructure:"enabled"`
	Interval     time.Duration `mapstructure:"interval"`
	LeaseTimeout time.Duration `mapstructure:"lease_timeout"`
}

type JobPurgeCfg struct {
	Enabled            bool          `mapstructure:"enabled"`
	Interval           time.Duration `mapstructure:"interval"`
	CompletedRetention time.Duration `mapstructure:"completed_retention"`
}

// NotifyConfig 是 notify 模块的可选外发通道配置。当前仅 webhook。
type NotifyConfig struct {
	Webhook WebhookCfg `mapstructure:"webhook"`
}

// WebhookCfg 是 webhook 通道的配置。enabled=false 时上层 dispatcher 仍会丢弃所有 webhook 消息。
type WebhookCfg struct {
	Enabled bool          `mapstructure:"enabled"`
	URL     string        `mapstructure:"url"`
	Secret  string        `mapstructure:"secret"`
	Timeout time.Duration `mapstructure:"timeout"`
	Topics  []string      `mapstructure:"topics"`
}

// Load 从（按优先级递增）默认值 → 配置文件（如有）→ 环境变量 加载配置。
// configFile 可为空字符串，仅用环境变量。
func Load(configFile string) (*Config, error) {
	v := viper.New()

	// 默认值
	v.SetDefault("env", "development")
	v.SetDefault("data_dir", "./data")
	v.SetDefault("http.addr", ":8080")
	v.SetDefault("workspace.data_dir", "./data")
	v.SetDefault("workspace.clone_timeout", "30m")
	v.SetDefault("workspace.fetch_timeout", "5m")
	v.SetDefault("workspace.push_timeout", "5m")
	v.SetDefault("workspace.ops_timeout", "60s")
	v.SetDefault("git.binary", "git")
	v.SetDefault("chat.attachment.max_file_size_mb", 20)
	v.SetDefault("chat.attachment.max_message_size_mb", 50)
	v.SetDefault("chat.attachment.mime_whitelist", []string{
		"image/png", "image/jpeg", "image/webp", "image/gif",
		"application/pdf", "text/*",
	})
	v.SetDefault("chat.stream.ring_buffer_retention_seconds", 300)
	v.SetDefault("chat.history.safety_margin_pct", 5.0)
	v.SetDefault("storage.driver", "localfs")
	v.SetDefault("storage.localfs.base_path", "./data/uploads")
	v.SetDefault("jobs.enabled", true)
	v.SetDefault("jobs.workers", 2)
	v.SetDefault("jobs.shutdown_grace", "30s")
	v.SetDefault("jobs.workspace_fetch.enabled", true)
	v.SetDefault("jobs.workspace_fetch.interval", "5m")
	v.SetDefault("jobs.worktree_prune.enabled", true)
	v.SetDefault("jobs.worktree_prune.interval", "24h")
	v.SetDefault("jobs.worktree_prune.idle_threshold", "720h")
	v.SetDefault("jobs.worktree_prune.warning_lead", "72h")
	v.SetDefault("jobs.attachment_cleanup.enabled", true)
	v.SetDefault("jobs.attachment_cleanup.interval", "24h")
	v.SetDefault("jobs.attachment_cleanup.retention", "720h")
	v.SetDefault("jobs.job_reaper.enabled", true)
	v.SetDefault("jobs.job_reaper.interval", "1m")
	v.SetDefault("jobs.job_reaper.lease_timeout", "5m")
	v.SetDefault("jobs.job_purge.enabled", true)
	v.SetDefault("jobs.job_purge.interval", "24h")
	v.SetDefault("jobs.job_purge.completed_retention", "168h")
	v.SetDefault("notify.webhook.enabled", false)
	v.SetDefault("notify.webhook.timeout", "10s")

	if configFile != "" {
		v.SetConfigFile(configFile)
		if err := v.ReadInConfig(); err != nil {
			return nil, fmt.Errorf("read config file: %w", err)
		}
	}

	v.SetEnvPrefix("APP")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	v.AutomaticEnv()

	// 显式绑定无默认值的嵌套键，以便 Unmarshal 能从环境变量取值。
	// （AutomaticEnv 仅对 v.Get* 直接查询生效；Unmarshal 只看 viper 已知的键集合。）
	for _, key := range []string{
		"db.dsn",
		"bootstrap.admin_email",
		"bootstrap.admin_password",
		"master_key",
	} {
		if err := v.BindEnv(key); err != nil {
			return nil, fmt.Errorf("bind env %s: %w", key, err)
		}
	}

	var cfg Config
	if err := v.Unmarshal(&cfg); err != nil {
		return nil, fmt.Errorf("unmarshal config: %w", err)
	}

	// MasterKey 是 hex 字符串，需要单独解码
	rawKey := v.GetString("master_key")
	if rawKey == "" {
		return nil, fmt.Errorf("APP_MASTER_KEY required")
	}
	key, err := hex.DecodeString(rawKey)
	if err != nil {
		return nil, fmt.Errorf("APP_MASTER_KEY invalid hex: %w", err)
	}
	if len(key) != 32 {
		return nil, fmt.Errorf("APP_MASTER_KEY must be 32 bytes (got %d)", len(key))
	}
	cfg.MasterKey = MasterKey(key)

	if cfg.DB.DSN == "" {
		return nil, fmt.Errorf("APP_DB_DSN required")
	}
	return &cfg, nil
}