package companion

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"sort"
	"strconv"
	"time"
	"unicode/utf8"

	"longheng.io/server/internal/modules/dnf/repository"
)

// Profile is developer-owned evidence, never a client-submitted capability.
type Profile struct {
	ID                  string
	Version             uint32
	EvidenceID          string
	ClientSHA256        string
	PVFSHA256           string
	Job                 uint8
	GrowType            uint8
	BasicAttackVerified bool
	SkillLevelLimits    map[int64]int
}

// There are no accepted native profiles yet. Tests use synthetic profiles
// only to exercise policies; those profiles are not shipped in this registry.
func VerifiedProfiles() []Profile { return nil }

func validHash(value string) bool {
	decoded, err := hex.DecodeString(value)
	return err == nil && len(decoded) == 32 && hex.EncodeToString(decoded) == value
}

func (p Profile) validate(client, pvf string) error {
	if !validIdentity(p.ID) || p.Version == 0 || !validIdentity(p.EvidenceID) || !p.BasicAttackVerified {
		return ErrProfile
	}
	if !validHash(client) || !validHash(pvf) || client != p.ClientSHA256 || pvf != p.PVFSHA256 {
		return ErrAssets
	}
	return nil
}

type Selection struct {
	AccountID         string
	OwnerCharacterID  string
	SourceCharacterID string
	OnlineStateKnown  bool
	SourceOnline      bool
	ClientSHA256      string
	PVFSHA256         string
}

type EquipmentSpec struct {
	Slot   int16 `json:"slot"`
	ItemID int64 `json:"item_id"`
}
type SkillSpec struct {
	ID    int64 `json:"id"`
	Level int   `json:"level"`
}
type Exclusion struct {
	Kind   string `json:"kind"`
	ID     int64  `json:"id,omitempty"`
	Reason string `json:"reason"`
}

// Snapshot contains declarative template IDs, not inventory serials, raw
// item-instance bytes, live pointers, source cooldowns, wallets or quests.
// It is NOT the native ABI or a claim of gear/stat projection parity.
type Snapshot struct {
	SchemaVersion     int             `json:"schema_version"`
	AccountID         string          `json:"account_id"`
	OwnerCharacterID  string          `json:"owner_character_id"`
	SourceCharacterID string          `json:"source_character_id"`
	Name              string          `json:"name"`
	Job               uint8           `json:"job"`
	GrowType          uint8           `json:"grow_type"`
	Level             int             `json:"level"`
	ProfileID         string          `json:"profile_id"`
	ProfileVersion    uint32          `json:"profile_version"`
	ClientSHA256      string          `json:"client_sha256"`
	PVFSHA256         string          `json:"pvf_sha256"`
	Equipment         []EquipmentSpec `json:"equipment"`
	Skills            []SkillSpec     `json:"skills"`
	Exclusions        []Exclusion     `json:"exclusions"`
}

// Prepare consumes a single transaction's detached source state. The caller
// must keep the source offline check valid through preparation/run binding.
// It does not load or save repositories and cannot enable a native adapter.
func Prepare(source repository.CompanionSourceState, s Selection, p Profile, now time.Time) (Snapshot, error) {
	if !validIdentity(s.AccountID) || !validCharacterID(s.OwnerCharacterID) || !validCharacterID(s.SourceCharacterID) {
		return Snapshot{}, ErrSelection
	}
	if s.OwnerCharacterID == s.SourceCharacterID {
		return Snapshot{}, ErrSelf
	}
	if source.Owner.CharacterID != s.OwnerCharacterID || source.Source.CharacterID != s.SourceCharacterID ||
		source.Owner.Stats["delete_flag"] != 0 || source.Source.Stats["delete_flag"] != 0 {
		return Snapshot{}, ErrSource
	}
	if source.Owner.AccountID != s.AccountID || source.Source.AccountID != s.AccountID {
		return Snapshot{}, ErrAccount
	}
	if !s.OnlineStateKnown {
		return Snapshot{}, ErrOnlineUnknown
	}
	if s.SourceOnline {
		return Snapshot{}, ErrOnline
	}
	if err := p.validate(s.ClientSHA256, s.PVFSHA256); err != nil {
		return Snapshot{}, err
	}
	job, err := strconv.ParseUint(source.Source.Job, 10, 8)
	grow, hasGrow := source.Source.Stats["grow_type"]
	if err != nil || !hasGrow || grow < 0 || grow > 255 || uint8(job) != p.Job || uint8(grow) != p.GrowType {
		return Snapshot{}, ErrProfile
	}
	if now.IsZero() || source.Source.Level < 1 || source.Source.Level > 90 ||
		!validIdentity(source.Source.Name) || !utf8.ValidString(source.Source.Name) || !source.HasEquipment || !source.HasSkill ||
		source.Equipment.CharacterID != s.SourceCharacterID || source.Skill.CharacterID != s.SourceCharacterID {
		return Snapshot{}, ErrSnapshot
	}
	if len(source.Equipment.Entries) > 64 || len(source.Skill.Skills) > 1024 {
		return Snapshot{}, ErrSnapshot
	}
	out := Snapshot{SchemaVersion: 1, AccountID: s.AccountID, OwnerCharacterID: s.OwnerCharacterID,
		SourceCharacterID: s.SourceCharacterID, Name: source.Source.Name, Job: uint8(job), GrowType: uint8(grow),
		Level: source.Source.Level, ProfileID: p.ID, ProfileVersion: p.Version,
		ClientSHA256: s.ClientSHA256, PVFSHA256: s.PVFSHA256,
		Equipment: []EquipmentSpec{}, Skills: []SkillSpec{}, Exclusions: []Exclusion{
			{Kind: "attributes", Reason: "native_base_stats_and_equipment_projection_not_verified"},
			{Kind: "equipment", Reason: "instance_options_set_and_proc_effects_not_projected"},
		}}
	slots := map[int16]bool{}
	for _, item := range source.Equipment.Entries {
		if item.SlotIndex < 0 || item.SlotIndex > 255 || item.ItemID <= 0 || item.ItemID > int64(^uint32(0)) || slots[item.SlotIndex] {
			return Snapshot{}, ErrSnapshot
		}
		slots[item.SlotIndex] = true
		if !item.ExpireAt.IsZero() && !item.ExpireAt.After(now) {
			out.Exclusions = append(out.Exclusions, Exclusion{Kind: "equipment", ID: item.ItemID, Reason: "expired"})
			continue
		}
		out.Equipment = append(out.Equipment, EquipmentSpec{Slot: item.SlotIndex, ItemID: item.ItemID})
	}
	for id, skill := range source.Skill.Skills {
		if id <= 0 || id > 65535 || skill.Level < 0 || skill.Level > 65535 {
			return Snapshot{}, ErrSnapshot
		}
		if !skill.Enabled || skill.Level == 0 {
			continue
		}
		limit, supported := p.SkillLevelLimits[id]
		if !supported || limit <= 0 || skill.Level > limit {
			out.Exclusions = append(out.Exclusions, Exclusion{Kind: "skill", ID: id, Reason: "native_skill_or_level_unverified"})
			continue
		}
		out.Skills = append(out.Skills, SkillSpec{ID: id, Level: skill.Level})
	}
	sort.Slice(out.Equipment, func(i, j int) bool { return out.Equipment[i].Slot < out.Equipment[j].Slot })
	sort.Slice(out.Skills, func(i, j int) bool { return out.Skills[i].ID < out.Skills[j].ID })
	sort.Slice(out.Exclusions, func(i, j int) bool {
		a, b := out.Exclusions[i], out.Exclusions[j]
		if a.Kind != b.Kind {
			return a.Kind < b.Kind
		}
		if a.ID != b.ID {
			return a.ID < b.ID
		}
		return a.Reason < b.Reason
	})
	return out, nil
}

func (s Snapshot) Clone() Snapshot {
	if s.Equipment != nil {
		s.Equipment = append([]EquipmentSpec{}, s.Equipment...)
	}
	if s.Skills != nil {
		s.Skills = append([]SkillSpec{}, s.Skills...)
	}
	if s.Exclusions != nil {
		s.Exclusions = append([]Exclusion{}, s.Exclusions...)
	}
	return s
}

// Fingerprint is content addressing, NOT an authentication token.
func (s Snapshot) Fingerprint() string {
	body, _ := json.Marshal(s)
	sum := sha256.Sum256(body)
	return hex.EncodeToString(sum[:])
}