package mysql

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

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

// workflowCheckpoint 是待续表中版本化的内部唤醒身份；不保存内存执行栈或新的业务预算。
type workflowCheckpoint struct {
	SchemaVersion uint32   `json:"schema_version"`          // SchemaVersion 当前结构版本为1，未知版本禁止推进。
	Kind          string   `json:"kind"`                    // Kind 为ROOT、TIMER、SIGNAL或POLL，决定实际权威记录的读取方式。
	ActivationID  *core.ID `json:"activation_id,omitempty"` // ActivationID 固定等待激活；ROOT不使用该字段。
}

func saveWorkflowClock(ctx context.Context, tx *sql.Tx, g *workflowGraph, row *workflowStep, kind string, expected uint64, due time.Time) error {
	id, err := core.NewID()
	if err != nil {
		return err
	}
	if row.view.ActivationID == nil || kind != "TIMER" && kind != "POLL" && kind != "SIGNAL" {
		return errors.New("workflow clock identity invalid")
	}
	raw, err := json.Marshal(workflowCheckpoint{1, kind, row.view.ActivationID})
	if err != nil {
		return err
	}
	_, err = tx.ExecContext(ctx, `INSERT INTO weave_pending_advances(namespace_id,id,workflow_id,step_id,expected_step_revision,checkpoint,available_at) VALUES (?,?,?,?,?,?,?) ON DUPLICATE KEY UPDATE expected_step_revision=VALUES(expected_step_revision),checkpoint=VALUES(checkpoint),available_at=VALUES(available_at),revision=revision+1,updated_at=UTC_TIMESTAMP(6)`, g.view.NamespaceID, id, g.view.ID, row.view.ID, expected, string(raw), due)
	return err
}
func deleteWorkflowClock(ctx context.Context, tx *sql.Tx, g *workflowGraph, row *workflowStep) error {
	_, err := tx.ExecContext(ctx, `DELETE FROM weave_pending_advances WHERE namespace_id=? AND workflow_id=? AND step_id=?`, g.view.NamespaceID, g.view.ID, row.view.ID)
	return err
}

func (r *WorkflowRuntime) advanceClock(ctx context.Context, tx *sql.Tx, g *workflowGraph, c workflowCandidate, step core.ID, expected uint64, checkpoint workflowCheckpoint, allow bool, now time.Time) (bool, error) {
	var row *workflowStep
	for _, candidate := range g.steps {
		if candidate.view.ID == step {
			row = candidate
			break
		}
	}
	if row == nil || checkpoint.ActivationID == nil || string(row.view.Kind) != checkpoint.Kind || expected > row.view.Revision {
		return false, errors.New("workflow clock checkpoint mismatch")
	}
	if row.view.ActivationID == nil || *row.view.ActivationID != *checkpoint.ActivationID || g.view.State.Terminal() {
		return false, deleteWorkflowClock(ctx, tx, g, row)
	}
	if row.view.State != weave.StepActive && row.view.State != weave.StepWaiting {
		return false, deleteWorkflowClock(ctx, tx, g, row)
	}
	if g.view.StopKind != nil {
		if err := saveWorkflowAdvance(ctx, tx, g, now); err != nil {
			return false, err
		}
		return false, deleteWorkflowClock(ctx, tx, g, row)
	}
	if checkpoint.Kind == "POLL" {
		node, _ := g.program.Step(row.view.Key)
		if node.Poll.FinalSignal != nil {
			handled, changed, reason, err := r.driveWorkflowSignal(ctx, tx, g, row, c, nil, allow, now)
			if err != nil {
				return false, err
			}
			if handled {
				if changed && reason != "" {
					return true, r.audit(ctx, tx, g, c.id, reason, now)
				}
				return changed, nil
			}
		}
		return r.advancePoll(ctx, tx, g, row, c, allow, now)
	}
	if checkpoint.Kind == "SIGNAL" {
		return r.advanceSignalClock(ctx, tx, g, row, c, allow, now)
	}
	if checkpoint.Kind != "TIMER" || row.view.State != weave.StepWaiting {
		return false, errors.New("workflow timer state invalid")
	}
	var wait core.ID
	var deadline time.Time
	var kind, state string
	var name, version sql.NullString
	var correlation []byte
	var count int
	if err := tx.QueryRowContext(ctx, `SELECT COUNT(*) FROM weave_waits WHERE namespace_id=? AND workflow_id=? AND activation_id=?`, c.ns, c.workflow, checkpoint.ActivationID).Scan(&count); err != nil {
		return false, err
	}
	if count != 1 {
		return false, errors.New("workflow timer wait set invalid")
	}
	if err := tx.QueryRowContext(ctx, `SELECT id,kind,state,deadline_at,signal_name,payload_version,correlation_key FROM weave_waits WHERE namespace_id=? AND workflow_id=? AND activation_id=? FOR UPDATE`, c.ns, c.workflow, checkpoint.ActivationID).Scan(&wait, &kind, &state, &deadline, &name, &version, &correlation); err != nil {
		return false, err
	}
	node, _ := g.program.Step(row.view.Key)
	origin, err := workflowActivationOrigin(ctx, tx, g, row)
	if err != nil {
		return false, err
	}
	intended := origin.started.Add(time.Duration(node.Timer.DelayMS) * time.Millisecond)
	if kind != "TIMER" || state != "WAITING" || name.Valid || version.Valid || len(correlation) != 0 || !deadline.Equal(minimumTime(intended, g.view.DeadlineAt)) {
		return false, errors.New("workflow timer wait invalid")
	}
	if now.Before(deadline) {
		return false, saveWorkflowClock(ctx, tx, g, row, "TIMER", row.view.Revision, deadline)
	}
	state, reason, stepState := "SATISFIED", "TIMER_ELAPSED", weave.StepSucceeded
	output := json.RawMessage(`null`)
	if intended.After(g.view.DeadlineAt) {
		state, reason, stepState, output = "EXPIRED", "TIMER_WORKFLOW_DEADLINE", weave.StepNeedsReview, nil
	}
	res, err := tx.ExecContext(ctx, `UPDATE weave_waits SET state=?,resolved_at=?,revision=revision+1,updated_at=? WHERE namespace_id=? AND id=? AND state='WAITING'`, state, now, now, c.ns, wait)
	if err := exactlyOne(res, err); err != nil {
		return false, err
	}
	if err := saveWorkflowResultStep(ctx, tx, g, row, stepState, output, now); err != nil {
		return false, err
	}
	if err := deleteWorkflowClock(ctx, tx, g, row); err != nil {
		return false, err
	}
	if stepState == weave.StepNeedsReview {
		if err := holdWorkflow(ctx, tx, g, weave.InstanceNeedsReview, reason, now); err != nil {
			return false, err
		}
	} else if err := r.progress(ctx, tx, g, allow, now); err != nil {
		return false, err
	}
	return true, r.audit(ctx, tx, g, c.id, reason, now)
}