package mysql

import (
	"bytes"
	"context"
	"database/sql"
	"encoding/base64"
	"encoding/json"
	"errors"
	"time"

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

// historyCursor 只定位已授权父资源中的后续位置，不作为身份或授权证明。
type historyCursor struct {
	Version   int        `json:"v"`
	Kind      string     `json:"k"`
	Namespace core.ID    `json:"n"`
	Task      core.ID    `json:"t"`
	Attempt   core.ID    `json:"a,omitempty"`
	Epoch     uint64     `json:"e,omitempty,string"`
	Created   *time.Time `json:"c,omitempty"`
	ID        core.ID    `json:"i,omitempty"`
}

func decodeHistoryCursor(value string, ns, task, attempt core.ID) (historyCursor, error) {
	var c historyCursor
	raw, err := base64.RawURLEncoding.Strict().DecodeString(value)
	if err != nil || len(raw) > 768 {
		return c, fault.Invalid("invalid history cursor")
	}
	if _, err := jsonvalue.Canonical(raw); err != nil {
		return c, fault.Invalid("invalid history cursor")
	}
	var fields map[string]json.RawMessage
	if json.Unmarshal(raw, &fields) != nil || fields == nil {
		return c, fault.Invalid("invalid history cursor")
	}
	for k := range fields {
		switch k {
		case "v", "k", "n", "t", "a", "e", "c", "i":
		default:
			return c, fault.Invalid("invalid history cursor")
		}
	}
	d := json.NewDecoder(bytes.NewReader(raw))
	d.DisallowUnknownFields()
	if d.Decode(&c) != nil || c.Version != 1 || c.Namespace != ns || c.Task != task || c.Attempt != attempt {
		return c, fault.Invalid("cursor does not match this history query")
	}
	if attempt == "" {
		if c.Kind != "attempts" || c.Epoch == 0 || c.ID != "" || c.Created != nil {
			return c, fault.Invalid("invalid attempts cursor")
		}
	} else {
		if c.Kind != "evidence" || c.Epoch != 0 || c.ID.Validate() != nil || c.Created == nil || c.Created.Year() < 2000 || c.Created.Year() > 9998 || c.Created.Nanosecond()%1000 != 0 {
			return c, fault.Invalid("invalid evidence cursor")
		}
	}
	return c, nil
}
func encodeHistoryCursor(c historyCursor) (string, error) {
	raw, err := json.Marshal(c)
	return base64.RawURLEncoding.EncodeToString(raw), err
}
func authorizeHistoryTask(ctx context.Context, tx *sql.Tx, ns, task core.ID, p auth.Permissions) error {
	var queue core.ID
	err := tx.QueryRowContext(ctx, `SELECT queue_id FROM pulse_tasks WHERE namespace_id=? AND id=?`, ns, task).Scan(&queue)
	if errors.Is(err, sql.ErrNoRows) {
		return fault.NotFound
	}
	if err != nil {
		return err
	}
	if !p.AllowsQueue(queue) {
		return fault.NotFound
	}
	return nil
}
func historyAttemptExists(ctx context.Context, tx *sql.Tx, ns, task, attempt core.ID) error {
	var found core.ID
	err := tx.QueryRowContext(ctx, `SELECT id FROM pulse_attempts WHERE namespace_id=? AND task_id=? AND id=?`, ns, task, attempt).Scan(&found)
	if errors.Is(err, sql.ErrNoRows) {
		return fault.NotFound
	}
	return err
}

const attemptHistoryColumns = `a.id,a.task_id,a.epoch,a.state,a.revision,a.lease_until,a.authorized_at,a.ended_at,COALESCE(a.error_code,''),a.retryable,a.created_at,a.updated_at,a.concurrency_token`

func scanAttemptSummary(row interface{ Scan(...any) error }) (service.AttemptSummary, error) {
	var a service.AttemptSummary
	err := row.Scan(&a.ID, &a.TaskID, &a.Epoch, &a.State, &a.Revision, &a.LeaseUntil, &a.AuthorizedAt, &a.EndedAt, &a.ErrorCode, &a.Retryable, &a.CreatedAt, &a.UpdatedAt, &a.ConcurrencyToken)
	return a, err
}
func (s *TaskStore) ListTaskAttempts(ctx context.Context, t auth.Token, task core.ID, in service.HistoryPageInput) (service.AttemptPage, error) {
	out := service.AttemptPage{Items: []service.AttemptSummary{}}
	err := s.transaction(ctx, t, "tasks:read", func(tx *sql.Tx, p auth.Permissions) error {
		if err := authorizeHistoryTask(ctx, tx, t.NamespaceID, task, p); err != nil {
			return err
		}
		q := `SELECT ` + attemptHistoryColumns + ` FROM pulse_attempts a WHERE a.namespace_id=? AND a.task_id=?`
		args := []any{t.NamespaceID, task}
		if in.Cursor != "" {
			c, err := decodeHistoryCursor(in.Cursor, t.NamespaceID, task, "")
			if err != nil {
				return err
			}
			q += ` AND a.epoch<?`
			args = append(args, c.Epoch)
		}
		q += ` ORDER BY a.epoch DESC LIMIT ?`
		args = append(args, in.Limit+1)
		rows, err := tx.QueryContext(ctx, q, args...)
		if err != nil {
			return err
		}
		defer rows.Close()
		for rows.Next() {
			a, err := scanAttemptSummary(rows)
			if err != nil {
				return err
			}
			out.Items = append(out.Items, a)
		}
		if err := rows.Err(); err != nil {
			return err
		}
		if len(out.Items) > in.Limit {
			out.Items = out.Items[:in.Limit]
			last := out.Items[len(out.Items)-1]
			out.NextCursor, err = encodeHistoryCursor(historyCursor{Version: 1, Kind: "attempts", Namespace: t.NamespaceID, Task: task, Epoch: last.Epoch})
			return err
		}
		return nil
	})
	return out, err
}
func (s *TaskStore) GetTaskAttempt(ctx context.Context, t auth.Token, task, attempt core.ID) (service.AttemptView, error) {
	var out service.AttemptView
	err := s.transaction(ctx, t, "tasks:read", func(tx *sql.Tx, p auth.Permissions) error {
		if err := authorizeHistoryTask(ctx, tx, t.NamespaceID, task, p); err != nil {
			return err
		}
		var result []byte
		err := tx.QueryRowContext(ctx, `SELECT `+attemptHistoryColumns+`,a.session_id,w.worker_instance_id,a.result FROM pulse_attempts a JOIN pulse_worker_sessions w ON w.namespace_id=a.namespace_id AND w.id=a.session_id WHERE a.namespace_id=? AND a.task_id=? AND a.id=?`, t.NamespaceID, task, attempt).Scan(&out.ID, &out.TaskID, &out.Epoch, &out.State, &out.Revision, &out.LeaseUntil, &out.AuthorizedAt, &out.EndedAt, &out.ErrorCode, &out.Retryable, &out.CreatedAt, &out.UpdatedAt, &out.ConcurrencyToken, &out.SessionID, &out.WorkerInstanceID, &result)
		if errors.Is(err, sql.ErrNoRows) {
			return fault.NotFound
		}
		out.Result = result
		return err
	})
	return out, err
}
func (s *TaskStore) ListAttemptEvidence(ctx context.Context, t auth.Token, task, attempt core.ID, in service.HistoryPageInput) (service.EvidencePage, error) {
	out := service.EvidencePage{Items: []service.EvidenceSummary{}}
	err := s.transaction(ctx, t, "tasks:read", func(tx *sql.Tx, p auth.Permissions) error {
		if err := authorizeHistoryTask(ctx, tx, t.NamespaceID, task, p); err != nil {
			return err
		}
		if err := historyAttemptExists(ctx, tx, t.NamespaceID, task, attempt); err != nil {
			return err
		}
		q := `SELECT id,attempt_id,outcome,COALESCE(error_code,''),retryable,reason,created_at FROM pulse_attempt_evidence WHERE namespace_id=? AND attempt_id=?`
		args := []any{t.NamespaceID, attempt}
		if in.Cursor != "" {
			c, err := decodeHistoryCursor(in.Cursor, t.NamespaceID, task, attempt)
			if err != nil {
				return err
			}
			q += ` AND (created_at<? OR (created_at=? AND id<?))`
			args = append(args, *c.Created, *c.Created, c.ID)
		}
		q += ` ORDER BY created_at DESC,id DESC LIMIT ?`
		args = append(args, in.Limit+1)
		rows, err := tx.QueryContext(ctx, q, args...)
		if err != nil {
			return err
		}
		defer rows.Close()
		for rows.Next() {
			e := service.EvidenceSummary{TaskID: task, Disposition: "EVIDENCE_ONLY"}
			if err := rows.Scan(&e.ID, &e.AttemptID, &e.Outcome, &e.ErrorCode, &e.Retryable, &e.Reason, &e.CreatedAt); err != nil {
				return err
			}
			out.Items = append(out.Items, e)
		}
		if err := rows.Err(); err != nil {
			return err
		}
		if len(out.Items) > in.Limit {
			out.Items = out.Items[:in.Limit]
			last := out.Items[len(out.Items)-1]
			out.NextCursor, err = encodeHistoryCursor(historyCursor{Version: 1, Kind: "evidence", Namespace: t.NamespaceID, Task: task, Attempt: attempt, Created: &last.CreatedAt, ID: last.ID})
			return err
		}
		return nil
	})
	return out, err
}
func (s *TaskStore) GetAttemptEvidence(ctx context.Context, t auth.Token, task, attempt, evidence core.ID) (service.EvidenceView, error) {
	out := service.EvidenceView{EvidenceSummary: service.EvidenceSummary{TaskID: task, Disposition: "EVIDENCE_ONLY"}}
	err := s.transaction(ctx, t, "tasks:read", func(tx *sql.Tx, p auth.Permissions) error {
		if err := authorizeHistoryTask(ctx, tx, t.NamespaceID, task, p); err != nil {
			return err
		}
		if err := historyAttemptExists(ctx, tx, t.NamespaceID, task, attempt); err != nil {
			return err
		}
		var payload []byte
		err := tx.QueryRowContext(ctx, `SELECT id,attempt_id,outcome,COALESCE(error_code,''),retryable,reason,created_at,message_id,payload FROM pulse_attempt_evidence WHERE namespace_id=? AND attempt_id=? AND id=?`, t.NamespaceID, attempt, evidence).Scan(&out.ID, &out.AttemptID, &out.Outcome, &out.ErrorCode, &out.Retryable, &out.Reason, &out.CreatedAt, &out.MessageID, &payload)
		if errors.Is(err, sql.ErrNoRows) {
			return fault.NotFound
		}
		out.Payload = payload
		return err
	})
	return out, err
}