package mysql

import (
	"context"
	"crypto/sha256"
	"database/sql"
	"encoding/json"
	"fmt"
	"strings"
	"time"
	"unicode/utf8"

	"git.yuntuo.hk/k2safe/orbit/internal/fault"
	core "git.yuntuo.hk/k2safe/orbit/model"
	"git.yuntuo.hk/k2safe/orbit/platform/auth"
)

const (
	credentialOperationVersion = 1
	credentialRotateAction     = "ROTATE"
	credentialRevokeAction     = "REVOKE"
	credentialOperationName    = "credential.change.v1"
)

// CredentialStatus 是管理读取的脱敏凭据状态；永远不包含秘密或摘要。
// Enabled 字段分别表示所属命名空间和应用当前是否允许业务认证。
type CredentialStatus struct {
	// NamespaceID 凭据所属命名空间标识。
	NamespaceID core.ID `json:"namespace_id"`
	// CredentialID 凭据记录标识，轮换时保持不变。
	CredentialID core.ID `json:"credential_id"`
	// Name 凭据的管理名称。
	Name string `json:"name"`
	// Revision 凭据的乐观并发版本，所有变更都必须核对它。
	Revision uint64 `json:"revision"`
	// ExpiresAt 当前秘密的到期时间；空值表示未设置到期时间。
	ExpiresAt *time.Time `json:"expires_at,omitempty"`
	// RevokedAt 撤销时间；空值表示尚未撤销。
	RevokedAt *time.Time `json:"revoked_at,omitempty"`
	// NamespaceEnabled 命名空间是否启用。
	NamespaceEnabled bool `json:"namespace_enabled"`
	// ApplicationEnabled 所属应用是否启用。
	ApplicationEnabled bool `json:"application_enabled"`
}

// CredentialChangeInput 描述一次待固定的管理变更。
// ExpectedRevision 防止准备和提交之间的并发变更被覆盖。
type CredentialChangeInput struct {
	// NamespaceID 凭据所属命名空间。
	NamespaceID core.ID
	// CredentialID 要变更的凭据。
	CredentialID core.ID
	// ExpectedRevision 准备操作时观察到的版本。
	ExpectedRevision uint64
	// Action 只能是 ROTATE 或 REVOKE。
	Action string
	// ValidFor 轮换后的有效时长；撤销时必须为零。
	ValidFor time.Duration
	// Reason 必填审计原因。
	Reason string
}

// CredentialOperation 是可安全重放的私有操作文件内容。
// 令牌只存在于 ROTATE 文件中；服务端只保存其摘要和操作回执。
type CredentialOperation struct {
	// Version 操作文件格式版本，升级时不得静默改变语义。
	Version int `json:"version"`
	// OperationID 稳定操作身份，同时作为审计和幂等记录的身份。
	OperationID core.ID `json:"operation_id"`
	// NamespaceID 凭据所属命名空间。
	NamespaceID core.ID `json:"namespace_id"`
	// CredentialID 变更目标凭据。
	CredentialID core.ID `json:"credential_id"`
	// ExpectedRevision 只允许在该版本上首次应用。
	ExpectedRevision uint64 `json:"expected_revision"`
	// Action 固定为 ROTATE 或 REVOKE。
	Action string `json:"action"`
	// Reason 写入管理审计，不能包含控制字符或秘密。
	Reason string `json:"reason"`
	// Token 轮换产生的一次性新令牌；撤销操作为空。
	Token string `json:"token,omitempty"`
	// ExpiresAt 轮换后固定的绝对到期时间；重放不能重新计算。
	ExpiresAt *time.Time `json:"expires_at,omitempty"`
}

// CredentialChangeReceipt 是服务端保存并可重复返回的脱敏结果。
// Deduplicated 只表示本次调用命中了已有回执，不表示当前凭据仍处于该状态。
type CredentialChangeReceipt struct {
	// OperationID 稳定操作身份。
	OperationID core.ID `json:"operation_id"`
	// NamespaceID 操作所属命名空间。
	NamespaceID core.ID `json:"namespace_id"`
	// CredentialID 变更目标凭据。
	CredentialID core.ID `json:"credential_id"`
	// Action 已应用的变更类型。
	Action string `json:"action"`
	// Revision 该操作提交后凭据版本。
	Revision uint64 `json:"revision"`
	// AppliedAt 操作提交事务使用的数据库时间。
	AppliedAt time.Time `json:"applied_at"`
	// ExpiresAt 轮换后的固定到期时间。
	ExpiresAt *time.Time `json:"expires_at,omitempty"`
	// RevokedAt 撤销提交时间。
	RevokedAt *time.Time `json:"revoked_at,omitempty"`
	// Deduplicated 当前调用是否读取了既有回执。
	Deduplicated bool `json:"deduplicated"`
}

// GetCredentialStatus 读取脱敏状态，不需要使用该凭据认证。
func GetCredentialStatus(ctx context.Context, db *sql.DB, namespace, credential core.ID) (CredentialStatus, error) {
	var out CredentialStatus
	if err := validateCredentialIDs(namespace, credential); err != nil {
		return out, err
	}
	if err := CheckSchema(ctx, db); err != nil {
		return out, err
	}
	var expires, revoked sql.NullTime
	err := db.QueryRowContext(ctx, `SELECT c.name,c.revision,c.expires_at,c.revoked_at,n.enabled,a.enabled
        FROM orbit_credentials c
        JOIN orbit_namespaces n ON n.id=c.namespace_id
        JOIN orbit_applications a ON a.id=n.application_id
        WHERE c.namespace_id=? AND c.id=?`, namespace, credential).
		Scan(&out.Name, &out.Revision, &expires, &revoked, &out.NamespaceEnabled, &out.ApplicationEnabled)
	if err == sql.ErrNoRows {
		return out, fault.NotFound
	}
	if err != nil {
		return out, err
	}
	out.NamespaceID, out.CredentialID = namespace, credential
	out.ExpiresAt = nullableTime(expires)
	out.RevokedAt = nullableTime(revoked)
	return out, nil
}

// PrepareCredentialOperation 只读取当前状态并生成一次秘密，不修改数据库。
// 调用方应先把返回值写入受保护的新文件，再调用 ApplyCredentialOperation。
func PrepareCredentialOperation(ctx context.Context, db *sql.DB, in CredentialChangeInput) (CredentialOperation, error) {
	var out CredentialOperation
	if err := validateCredentialChangeInput(in); err != nil {
		return out, err
	}
	if err := CheckSchema(ctx, db); err != nil {
		return out, err
	}
	status, err := GetCredentialStatus(ctx, db, in.NamespaceID, in.CredentialID)
	if err != nil {
		return out, err
	}
	if status.Revision != in.ExpectedRevision || status.RevokedAt != nil {
		return out, fault.Conflict
	}
	var now time.Time
	if err := db.QueryRowContext(ctx, "SELECT UTC_TIMESTAMP(6)").Scan(&now); err != nil {
		return out, err
	}
	now = now.UTC()
	if in.Action == credentialRotateAction {
		secret, _, err := auth.Issue(in.NamespaceID, in.CredentialID)
		if err != nil {
			return out, err
		}
		out.Token = secret
		out.ExpiresAt = timePtr(now.Add(in.ValidFor))
	} else if in.ValidFor != 0 {
		return out, fault.Invalid("revoke operation cannot set validity")
	}
	out.Version = credentialOperationVersion
	out.NamespaceID = in.NamespaceID
	out.CredentialID = in.CredentialID
	out.ExpectedRevision = in.ExpectedRevision
	out.Action = in.Action
	out.Reason = in.Reason
	out.OperationID, err = core.NewID()
	if err != nil {
		return out, err
	}
	return out, ValidateCredentialOperation(out)
}

// ValidateCredentialOperation validates the exact private operation shape.
// It is exported so the admin CLI can reject tampered files before opening a DB.
func ValidateCredentialOperation(op CredentialOperation) error {
	if op.Version != credentialOperationVersion || op.OperationID.Validate() != nil || op.NamespaceID.Validate() != nil || op.CredentialID.Validate() != nil {
		return fault.Invalid("credential operation identity or version is invalid")
	}
	if op.ExpectedRevision == 0 || (op.Action != credentialRotateAction && op.Action != credentialRevokeAction) {
		return fault.Invalid("credential operation action or revision is invalid")
	}
	if err := validCredentialReason(op.Reason); err != nil {
		return err
	}
	if op.Action == credentialRotateAction {
		if op.ExpiresAt == nil || op.ExpiresAt.IsZero() || op.Token == "" {
			return fault.Invalid("rotation operation must contain a token and fixed expiry")
		}
		parsed, err := auth.Parse(op.Token)
		if err != nil || parsed.NamespaceID != op.NamespaceID || parsed.CredentialID != op.CredentialID {
			return fault.Invalid("rotation token does not match credential identity")
		}
	} else if op.Token != "" || op.ExpiresAt != nil {
		return fault.Invalid("revoke operation must not contain a token or expiry")
	}
	return nil
}

// ApplyCredentialOperation applies one frozen operation or returns its original
// receipt. No callback or file I/O occurs inside the transaction. A commit error
// is intentionally returned unchanged; replaying the same operation reconciles it.
func ApplyCredentialOperation(ctx context.Context, db *sql.DB, op CredentialOperation) (CredentialChangeReceipt, error) {
	var out CredentialChangeReceipt
	if err := ValidateCredentialOperation(op); err != nil {
		return out, err
	}
	if err := CheckSchema(ctx, db); err != nil {
		return out, err
	}
	err := WithTx(ctx, db, func(tx *sql.Tx) error {
		var name string
		var revision uint64
		var expires, revoked sql.NullTime
		var namespaceEnabled, applicationEnabled bool
		err := tx.QueryRowContext(ctx, `SELECT c.name,c.revision,c.expires_at,c.revoked_at,n.enabled,a.enabled
            FROM orbit_credentials c
            JOIN orbit_namespaces n ON n.id=c.namespace_id
            JOIN orbit_applications a ON a.id=n.application_id
            WHERE c.namespace_id=? AND c.id=? FOR UPDATE`, op.NamespaceID, op.CredentialID).
			Scan(&name, &revision, &expires, &revoked, &namespaceEnabled, &applicationEnabled)
		if err == sql.ErrNoRows {
			return fault.NotFound
		}
		if err != nil {
			return err
		}
		identity, cached, err := reserveCredentialOperation(ctx, tx, op)
		if err != nil {
			return err
		}
		if cached != nil {
			if err := json.Unmarshal(cached, &out); err != nil {
				return fmt.Errorf("stored credential receipt is invalid: %w", err)
			}
			out.Deduplicated = true
			return nil
		}
		if revision != op.ExpectedRevision || revoked.Valid {
			return fault.Conflict
		}
		if revision == ^uint64(0) {
			return fault.Conflict
		}
		now, err := dbNow(ctx, tx)
		if err != nil {
			return err
		}
		before := map[string]any{"name": name, "revision": revision, "expires_at": nullableTime(expires), "revoked_at": nullableTime(revoked), "namespace_enabled": namespaceEnabled, "application_enabled": applicationEnabled}
		after := map[string]any{"name": name, "revision": revision + 1, "namespace_enabled": namespaceEnabled, "application_enabled": applicationEnabled}
		if op.Action == credentialRotateAction {
			parsed, err := auth.Parse(op.Token)
			if err != nil {
				return fault.Invalid("rotation token is invalid")
			}
			if !op.ExpiresAt.After(now) || op.ExpiresAt.After(now.Add(365*24*time.Hour)) {
				return fault.Conflict
			}
			if _, err := tx.ExecContext(ctx, `UPDATE orbit_credentials
                SET secret_digest=?,expires_at=?,revoked_at=NULL,revision=revision+1,updated_at=?
                WHERE namespace_id=? AND id=? AND revision=?`, parsed.Digest, op.ExpiresAt.UTC(), now, op.NamespaceID, op.CredentialID, revision); err != nil {
				return err
			}
			out.ExpiresAt = timePtr(op.ExpiresAt.UTC())
			after["expires_at"] = out.ExpiresAt
		} else {
			if _, err := tx.ExecContext(ctx, `UPDATE orbit_credentials
                SET revoked_at=?,revision=revision+1,updated_at=?
                WHERE namespace_id=? AND id=? AND revision=?`, now, now, op.NamespaceID, op.CredentialID, revision); err != nil {
				return err
			}
			out.RevokedAt = timePtr(now)
			after["revoked_at"] = now
		}
		out.OperationID = op.OperationID
		out.NamespaceID = op.NamespaceID
		out.CredentialID = op.CredentialID
		out.Action = op.Action
		out.Revision = revision + 1
		out.AppliedAt = now
		actor, err := databaseActor(ctx, tx)
		if err != nil {
			return err
		}
		if err := appendCredentialAudit(ctx, tx, actor, op, before, after); err != nil {
			return err
		}
		encoded, err := json.Marshal(out)
		if err != nil {
			return err
		}
		if _, err := tx.ExecContext(ctx, `UPDATE orbit_idempotency_keys SET response=?,revision=revision+1,updated_at=? WHERE namespace_id=? AND id=?`, encoded, now, op.NamespaceID, identity); err != nil {
			return err
		}
		return nil
	})
	return out, err
}

// reserveCredentialOperation stores the frozen request digest before mutation.
// The operation ID is also the idempotency row ID, so retries never mint a new
// secret or a second audit event.
func reserveCredentialOperation(ctx context.Context, tx *sql.Tx, op CredentialOperation) (core.ID, []byte, error) {
	digest, err := requestDigest(op)
	if err != nil {
		return "", nil, err
	}
	keyDigest := core.Digest(sha256.Sum256([]byte(op.OperationID)))
	_, err = tx.ExecContext(ctx, `INSERT INTO orbit_idempotency_keys(namespace_id,id,operation,scope_key,key_digest,request_digest,resource_kind,resource_id,response,expires_at)
		VALUES (?,?,?,?,?,?,?,?,JSON_OBJECT(),DATE_ADD(UTC_TIMESTAMP(6),INTERVAL 90 DAY))
		ON DUPLICATE KEY UPDATE id=orbit_idempotency_keys.id`, op.NamespaceID, op.OperationID, credentialOperationName, string(op.CredentialID), keyDigest, digest, "credential", op.CredentialID)
	if err != nil {
		return "", nil, err
	}
	var storedID core.ID
	var storedDigest core.Digest
	var response []byte
	if err := tx.QueryRowContext(ctx, `SELECT id,request_digest,response FROM orbit_idempotency_keys
		WHERE namespace_id=? AND operation=? AND scope_key=? AND key_digest=? FOR UPDATE`, op.NamespaceID, credentialOperationName, string(op.CredentialID), keyDigest).
		Scan(&storedID, &storedDigest, &response); err != nil {
		return "", nil, err
	}
	if subtleCompareDigest(digest, storedDigest) != 1 {
		return "", nil, fault.IdempotencyConflict
	}
	trimmed := strings.TrimSpace(string(response))
	if trimmed != "" && trimmed != "{}" && trimmed != "null" {
		return storedID, response, nil
	}
	return storedID, nil, nil
}

func appendCredentialAudit(ctx context.Context, tx *sql.Tx, actor string, op CredentialOperation, before, after any) error {
	return appendAuditActor(ctx, tx, op.NamespaceID, actor, op.OperationID, strings.ToLower("credential."+strings.ToLower(op.Action)), op.CredentialID, op.Reason, before, after)
}

func appendAuditActor(ctx context.Context, tx *sql.Tx, namespace core.ID, actor string, operation core.ID, action string, resource core.ID, reason string, before, after any) error {
	old, err := json.Marshal(before)
	if err != nil {
		return err
	}
	current, err := json.Marshal(after)
	if err != nil {
		return err
	}
	id, err := core.NewID()
	if err != nil {
		return err
	}
	_, err = tx.ExecContext(ctx, `INSERT INTO orbit_audit_events(namespace_id,id,operation_id,actor_id,action,resource_kind,resource_id,reason,evidence_ref,`+"`before`"+`,`+"`after`"+`)
		VALUES (?,?,?,?,?,?,?,?,NULL,?,?)`, namespace, id, operation, actor, action, "credential", resource, reason, string(old), string(current))
	return err
}

func databaseActor(ctx context.Context, tx *sql.Tx) (string, error) {
	var principal string
	if err := tx.QueryRowContext(ctx, "SELECT CURRENT_USER()").Scan(&principal); err != nil {
		return "", err
	}
	principal = "mysql:" + principal
	if len(principal) <= 128 {
		return principal, nil
	}
	sum := sha256.Sum256([]byte(principal))
	return fmt.Sprintf("mysql-sha256:%x", sum[:]), nil
}

func subtleCompareDigest(a, b core.Digest) int {
	var result byte
	for i := range a {
		result |= a[i] ^ b[i]
	}
	if result == 0 {
		return 1
	}
	return 0
}

func validateCredentialIDs(namespace, credential core.ID) error {
	if namespace.Validate() != nil || credential.Validate() != nil {
		return fault.Invalid("credential identity is invalid")
	}
	return nil
}

func validateCredentialChangeInput(in CredentialChangeInput) error {
	if err := validateCredentialIDs(in.NamespaceID, in.CredentialID); err != nil {
		return err
	}
	if in.ExpectedRevision == 0 || (in.Action != credentialRotateAction && in.Action != credentialRevokeAction) {
		return fault.Invalid("credential action and expected revision are required")
	}
	if err := validCredentialReason(in.Reason); err != nil {
		return err
	}
	if in.Action == credentialRotateAction && (in.ValidFor < time.Hour || in.ValidFor > 365*24*time.Hour) {
		return fault.Invalid("credential validity must be between one hour and one year")
	}
	if in.Action == credentialRevokeAction && in.ValidFor != 0 {
		return fault.Invalid("revoke operation cannot set validity")
	}
	return nil
}

func validCredentialReason(reason string) error {
	if strings.TrimSpace(reason) == "" || !utf8.ValidString(reason) || len([]rune(reason)) > 1024 || strings.ContainsAny(reason, "\x00\r\n") {
		return fault.Invalid("credential reason is required and must not contain control newlines")
	}
	return nil
}

func nullableTime(v sql.NullTime) *time.Time {
	if !v.Valid {
		return nil
	}
	t := v.Time.UTC()
	return &t
}

func timePtr(v time.Time) *time.Time {
	t := v.UTC()
	return &t
}