package mysql

import (
	"context"
	"database/sql"
	"encoding/hex"
	"encoding/json"
	"errors"
	"time"
	"unicode/utf8"

	core "git.yuntuo.hk/k2safe/orbit/model"
	"git.yuntuo.hk/k2safe/orbit/weave/definition"
	"git.yuntuo.hk/k2safe/orbit/weave/signal"
)

type workflowSignalWait struct {
	id                  core.ID
	sequence            uint32
	state, correlation  string
	deadline, activated time.Time
	winner              *core.ID
	contract            *definition.Signal
}

// readWorkflowSignalWait 读取已经冻结的等待身份，不能把历史NULL元数据解释成有效信号契约。
func readWorkflowSignalWait(ctx context.Context, tx *sql.Tx, g *workflowGraph, row *workflowStep) (workflowSignalWait, error) {
	var w workflowSignalWait
	node, ok := g.program.Step(row.view.Key)
	w.contract = signalContract(node)
	if !ok || w.contract == nil || row.view.ActivationID == nil {
		return w, errors.New("signal step definition invalid")
	}
	var count int
	if err := tx.QueryRowContext(ctx, `SELECT COUNT(*) FROM weave_waits WHERE namespace_id=? AND workflow_id=? AND activation_id=?`, g.view.NamespaceID, g.view.ID, row.view.ActivationID).Scan(&count); err != nil {
		return w, err
	}
	if count != 1 {
		return w, errors.New("signal wait set invalid")
	}
	var name, version *string
	var kind string
	err := tx.QueryRowContext(ctx, `SELECT w.id,w.kind,w.state,w.signal_name,w.payload_version,w.correlation_key,w.deadline_at,w.winner_signal_id,a.sequence,a.created_at FROM weave_waits w JOIN weave_activations a ON a.namespace_id=w.namespace_id AND a.workflow_id=w.workflow_id AND a.id=w.activation_id AND a.step_id=? WHERE w.namespace_id=? AND w.workflow_id=? AND w.activation_id=? FOR UPDATE`, row.view.ID, g.view.NamespaceID, g.view.ID, row.view.ActivationID).Scan(&w.id, &kind, &w.state, &name, &version, &w.correlation, &w.deadline, &w.winner, &w.sequence, &w.activated)
	if err != nil {
		return w, err
	}
	if name == nil || version == nil {
		return w, workflowSourceError("SIGNAL_WAIT_UNVERIFIED")
	}
	if w.sequence == 0 || kind != string(row.view.Kind) || *name != w.contract.Name || *version != w.contract.PayloadVersion || !utf8.ValidString(w.correlation) || len(w.correlation) == 0 || len(w.correlation) > 512 || !w.deadline.Equal(minimumTime(g.view.DeadlineAt, w.activated.Add(time.Duration(w.contract.TimeoutMS)*time.Millisecond))) {
		return w, workflowSourceError("SIGNAL_WAIT_INVALID")
	}
	if node.Signal != nil {
		var input struct {
			Name        string `json:"name"`
			Version     string `json:"payload_version"`
			Correlation string `json:"correlation"`
		}
		if json.Unmarshal(row.input, &input) != nil || input.Name != *name || input.Version != *version || input.Correlation != w.correlation {
			return w, workflowSourceError("SIGNAL_ACTIVATION_INPUT_INVALID")
		}
	}
	return w, nil
}

// verifyWorkflowSignal 核对不可改写受理审计及请求摘要，防止可变状态读取替换原受理参数或时间。
func verifyWorkflowSignal(ctx context.Context, tx *sql.Tx, g *workflowGraph, row *workflowStep, w workflowSignalWait, v signal.View, now time.Time) error {
	if v.NamespaceID != g.view.NamespaceID || v.WorkflowID != g.view.ID || v.TargetStepKey != row.view.Key || v.TargetActivationSequence != w.sequence || v.CorrelationKey != w.correlation || v.Name != w.contract.Name || v.PayloadVersion != w.contract.PayloadVersion || v.AcceptedAt.After(now) || !v.AcceptedAt.Before(w.deadline) || !v.ExpiresAt.Equal(g.view.DeadlineAt) || definition.ValidateData(w.contract.PayloadType, v.Payload) != nil {
		return workflowSourceError("SIGNAL_IDENTITY_INVALID")
	}
	var digest core.Digest
	if err := tx.QueryRowContext(ctx, `SELECT request_digest FROM weave_signals WHERE namespace_id=? AND workflow_id=? AND id=?`, g.view.NamespaceID, g.view.ID, v.ID).Scan(&digest); err != nil {
		return err
	}
	var count int
	if err := tx.QueryRowContext(ctx, `SELECT COUNT(*) FROM orbit_audit_events WHERE namespace_id=? AND resource_kind='workflow_signal' AND resource_id=? AND action='workflow.signal'`, g.view.NamespaceID, v.ID).Scan(&count); err != nil {
		return err
	}
	if count != 1 {
		return workflowSourceError("SIGNAL_ACCEPTANCE_PROOF_MISSING")
	}
	var actor, reason string
	var evidence sql.NullString
	var raw []byte
	if err := tx.QueryRowContext(ctx, "SELECT actor_id,reason,evidence_ref,`after` FROM orbit_audit_events WHERE namespace_id=? AND resource_kind='workflow_signal' AND resource_id=? AND action='workflow.signal'", g.view.NamespaceID, v.ID).Scan(&actor, &reason, &evidence, &raw); err != nil {
		return err
	}
	var meta struct {
		SignalID   core.ID   `json:"signal_id"`
		WorkflowID core.ID   `json:"workflow_id"`
		Key        string    `json:"target_step_key"`
		Sequence   uint32    `json:"target_activation_sequence"`
		Digest     string    `json:"request_digest"`
		AcceptedAt time.Time `json:"accepted_at"`
		ExpiresAt  time.Time `json:"expires_at"`
	}
	if json.Unmarshal(raw, &meta) != nil || meta.SignalID != v.ID || meta.WorkflowID != g.view.ID || meta.Key != row.view.Key || meta.Sequence != w.sequence || meta.Digest != hex.EncodeToString(digest[:]) || !meta.AcceptedAt.Equal(v.AcceptedAt) || !meta.ExpiresAt.Equal(v.ExpiresAt) || actor != v.ActorID || evidence.String != v.EvidenceRef {
		return workflowSourceError("SIGNAL_ACCEPTANCE_PROOF_INVALID")
	}
	expected, err := requestDigest(signal.Input{Name: v.Name, PayloadVersion: v.PayloadVersion, TargetStepKey: v.TargetStepKey, TargetActivationSequence: v.TargetActivationSequence, CorrelationKey: v.CorrelationKey, Payload: v.Payload, Reason: reason, EvidenceRef: v.EvidenceRef})
	if err != nil {
		return err
	}
	if expected != digest {
		return workflowSourceError("SIGNAL_REQUEST_CHANGED")
	}
	return nil
}

// selectedWorkflowSignal 返回已胜出信号或最早按时受理的匹配信号；查询结果竞争由调用方在同一实例锁下裁决。
func selectedWorkflowSignal(ctx context.Context, tx *sql.Tx, g *workflowGraph, row *workflowStep, w workflowSignalWait, now time.Time) (*signal.View, error) {
	var id core.ID
	if w.winner != nil {
		if w.state != "SATISFIED" {
			return nil, workflowSourceError("SIGNAL_WINNER_WAIT_INVALID")
		}
		id = *w.winner
	} else {
		if w.state != "WAITING" {
			return nil, nil
		}
		err := tx.QueryRowContext(ctx, `SELECT id FROM weave_signals WHERE namespace_id=? AND workflow_id=? AND target_step_key=? AND target_activation_sequence=? AND state='PENDING' AND type=? AND payload_version=? AND correlation_key=? AND accepted_at<? ORDER BY accepted_at,id LIMIT 1 FOR UPDATE`, g.view.NamespaceID, g.view.ID, row.view.Key, w.sequence, w.contract.Name, w.contract.PayloadVersion, []byte(w.correlation), w.deadline).Scan(&id)
		if errors.Is(err, sql.ErrNoRows) {
			return nil, nil
		}
		if err != nil {
			return nil, err
		}
	}
	v, err := readWorkflowSignal(ctx, tx, g.view.NamespaceID, g.view.ID, id)
	if err != nil {
		return nil, err
	}
	if w.winner != nil && (v.State != "CONSUMED" || v.ConsumedWaitID == nil || *v.ConsumedWaitID != w.id) {
		return nil, workflowSourceError("SIGNAL_WINNER_ASSOCIATION_INVALID")
	}
	if err := verifyWorkflowSignal(ctx, tx, g, row, w, v, now); err != nil {
		return nil, err
	}
	return &v, nil
}

func claimWorkflowSignal(ctx context.Context, tx *sql.Tx, g *workflowGraph, w *workflowSignalWait, v *signal.View, now time.Time) error {
	if w.winner != nil {
		return nil
	}
	res, err := tx.ExecContext(ctx, `UPDATE weave_signals SET state='CONSUMED',disposition='WAIT_MATCHED',consumed_wait_id=?,revision=revision+1,updated_at=? WHERE namespace_id=? AND id=? AND workflow_id=? AND revision=? AND state='PENDING'`, w.id, now, g.view.NamespaceID, v.ID, g.view.ID, v.Revision)
	if err := exactlyOne(res, err); err != nil {
		return err
	}
	res, err = tx.ExecContext(ctx, `UPDATE weave_waits SET state='SATISFIED',winner_signal_id=?,resolved_at=?,revision=revision+1,updated_at=? WHERE namespace_id=? AND id=? AND workflow_id=? AND state='WAITING' AND winner_signal_id IS NULL`, v.ID, now, now, g.view.NamespaceID, w.id, g.view.ID)
	if err := exactlyOne(res, err); err != nil {
		return err
	}
	w.winner = &v.ID
	w.state = "SATISFIED"
	v.State = "CONSUMED"
	v.Revision++
	v.Disposition = "WAIT_MATCHED"
	v.ConsumedWaitID = &w.id
	return nil
}
func rejectOtherWorkflowSignals(ctx context.Context, tx *sql.Tx, g *workflowGraph, row *workflowStep, sequence uint32, reason string, now time.Time) error {
	_, err := tx.ExecContext(ctx, `UPDATE weave_signals SET state='REJECTED',disposition=?,revision=revision+1,updated_at=? WHERE namespace_id=? AND workflow_id=? AND target_step_key=? AND target_activation_sequence=? AND state='PENDING'`, reason, now, g.view.NamespaceID, g.view.ID, row.view.Key, sequence)
	return err
}