package domain

import (
	"errors"
	"strings"
	"time"
)

const (
	KeyModePlatform = "platform"
	KeyModeByok     = "byok"

	MeterAICopy     = "ai_copy"
	MeterAIResearch = "ai_research"
	MeterWebSearch  = "web_search"
	MeterAIImage    = "ai_image"

	PlanFree    = "free"
	PlanStarter = "starter"
	PlanPro     = "pro"
)

var (
	ErrNotFound      = errors.New("usage not found")
	ErrForbidden     = errors.New("usage forbidden")
	ErrNoKey         = errors.New("no api key configured (platform or byok)")
	ErrQuotaExceeded = errors.New("platform credits insufficient")
	// 分項點數上限（與 FE soft_caps 對齊；platform only）
	ErrMeterCapExceeded = errors.New("usage.err.meterCap")
	// 平台 key 無容量／限流：僅 BYOK 可繼續（不扣平台點）
	ErrPlatformCapacity = errors.New("usage.err.platformCapacity")
	ErrInvalidPlan      = errors.New("invalid plan")
)

type Event struct {
	ID        string `bson:"_id" json:"id"`
	UID       int64  `bson:"uid" json:"uid"`
	Meter     string `bson:"meter" json:"meter"`
	Credits   int    `bson:"credits" json:"credits"` // platform only; byok always 0
	KeyMode   string `bson:"key_mode" json:"key_mode"`
	Label     string `bson:"label" json:"label"`
	Source    string `bson:"source" json:"source"`
	MonthKey  string `bson:"month_key" json:"month_key"`
	CreatedAt int64  `bson:"created_at" json:"created_at"`
}

type MemberPrefs struct {
	UID       int64  `bson:"uid" json:"uid"`
	PlanID    string `bson:"plan_id" json:"plan_id"`
	Unlimited bool   `bson:"unlimited" json:"unlimited"`
	UpdatedAt int64  `bson:"updated_at" json:"updated_at"`
}

type Purchase struct {
	ID        string `bson:"_id" json:"id"`
	UID       int64  `bson:"uid" json:"uid"`
	PlanID    string `bson:"plan_id" json:"plan_id"`
	MockRef   string `bson:"mock_ref,omitempty" json:"mock_ref,omitempty"`
	CreatedAt int64  `bson:"created_at" json:"created_at"`
}

type PlanDef struct {
	ID             string
	MonthlyCredits int
	// SoftCaps：各 meter 點數硬上限（platform）；加總 = MonthlyCredits
	SoftCaps map[string]int
}

// Plans — 與 FE PLANS 同步（2026-07 · 組合毛利 ≥50%）
// 安全單價約 $0.012／點；Starter NT$590≈$18.4 / Pro NT$1990≈$62.2
// Free 120 點：夠用試用（可虧 ~$1.44 滿用）；付費扛回組合毛利。
var Plans = map[string]PlanDef{
	PlanFree: {
		ID: PlanFree, MonthlyCredits: 120,
		SoftCaps: map[string]int{
			MeterAICopy: 60, MeterAIResearch: 15, MeterWebSearch: 30, MeterAIImage: 15,
		},
	},
	PlanStarter: {
		ID: PlanStarter, MonthlyCredits: 600,
		SoftCaps: map[string]int{
			MeterAICopy: 300, MeterAIResearch: 90, MeterWebSearch: 150, MeterAIImage: 60,
		},
	},
	PlanPro: {
		ID: PlanPro, MonthlyCredits: 2000,
		SoftCaps: map[string]int{
			MeterAICopy: 1000, MeterAIResearch: 300, MeterWebSearch: 500, MeterAIImage: 200,
		},
	},
}

var DefaultCreditCost = map[string]int{
	MeterAICopy: 1, MeterAIResearch: 3, MeterWebSearch: 1, MeterAIImage: 5,
}

// ResolvePlan — 正規化 plan_id（小寫）並回傳方案；未知 → Free
func ResolvePlan(planID string) PlanDef {
	id := strings.ToLower(strings.TrimSpace(planID))
	if p, ok := Plans[id]; ok && p.ID != "" {
		return p
	}
	return Plans[PlanFree]
}

// MeterCost returns platform credit cost for one call.
func MeterCost(meter string) int {
	if c := DefaultCreditCost[meter]; c > 0 {
		return c
	}
	return 1
}

func NowNano() int64 { return time.Now().UTC().UnixNano() }

func MonthKey(nano int64) string {
	t := time.Unix(0, nano).UTC()
	return t.Format("2006-01")
}

func CurrentMonthKey() string { return MonthKey(NowNano()) }

// Summary split — never merge platform+byok into one total_calls only.
type MeterCount struct {
	Count   int `json:"count"`
	Credits int `json:"credits"`
}

type PlatformBlock struct {
	CreditsUsed      int                   `json:"credits_used"`
	CreditsRemaining int                   `json:"credits_remaining"`
	CreditsTotal     int                   `json:"credits_total"`
	CallCount        int                   `json:"call_count"`
	ByMeter          map[string]MeterCount `json:"by_meter"`
}

type ByokBlock struct {
	CallCount int                   `json:"call_count"`
	ByMeter   map[string]MeterCount `json:"by_meter"`
}

type MonthSummary struct {
	MonthKey  string        `json:"month_key"`
	UID       int64         `json:"uid"`
	PlanID    string        `json:"plan_id"`
	Unlimited bool          `json:"unlimited"`
	Platform  PlatformBlock `json:"platform"`
	Byok      ByokBlock     `json:"byok"`
	// Legacy FE bars: only platform credits (not mixed)
	TotalCredits     int `json:"total_credits"`
	RemainingCredits int `json:"remaining_credits"`
}

type TenantRow struct {
	UID                  int64  `json:"uid"`
	PlanID               string `json:"plan_id"`
	Unlimited            bool   `json:"unlimited"`
	PlatformCreditsUsed  int    `json:"platform_credits_used"`
	ByokCallCount        int    `json:"byok_call_count"`
}

type TenantSummary struct {
	MonthKey              string      `json:"month_key"`
	PlatformCreditsUsed   int         `json:"platform_credits_used"`
	ByokCallCount         int         `json:"byok_call_count"`
	Members               []TenantRow `json:"members"`
}