// Package session owns the daemon's in-memory state of truth and persists a
// snapshot on every change. Transitions go through the pure statemachine.
package session

import (
	"sync"
	"time"

	"antidrift/internal/domain"
	"antidrift/internal/statemachine"
	"antidrift/internal/store"
)

// Controller holds runtime state and the active commitment behind a mutex.
type Controller struct {
	mu           sync.Mutex
	runtimeState domain.RuntimeState
	commitment   *domain.Commitment
	deadline     time.Time
	snapshotPath string
}

// CommitmentView is the UI projection of the active commitment.
type CommitmentView struct {
	NextAction       string `json:"next_action"`
	SuccessCondition string `json:"success_condition"`
	TimeboxSecs      int64  `json:"timebox_secs"`
	DeadlineUnixSecs int64  `json:"deadline_unix_secs"`
}

// State is the broadcastable view of the controller.
type State struct {
	RuntimeState domain.RuntimeState `json:"runtime_state"`
	Commitment   *CommitmentView     `json:"commitment"`
}

// New loads any persisted snapshot, or starts Locked.
func New(snapshotPath string) (*Controller, error) {
	s, err := store.Load(snapshotPath)
	if err != nil {
		return nil, err
	}
	c := &Controller{
		runtimeState: s.RuntimeState,
		commitment:   s.Commitment,
		snapshotPath: snapshotPath,
	}
	if s.DeadlineUnixSecs > 0 {
		c.deadline = time.Unix(s.DeadlineUnixSecs, 0)
	}
	if c.runtimeState == "" {
		c.runtimeState = domain.RuntimeLocked
	}
	return c, nil
}

// State returns the current broadcastable state. Safe for concurrent use.
func (c *Controller) State() State {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.stateLocked()
}

// Deadline returns the active commitment deadline, or the zero time.
func (c *Controller) Deadline() time.Time {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.deadline
}

func (c *Controller) stateLocked() State {
	st := State{RuntimeState: c.runtimeState}
	if c.commitment != nil {
		st.Commitment = &CommitmentView{
			NextAction:       c.commitment.NextAction,
			SuccessCondition: c.commitment.SuccessCondition,
			TimeboxSecs:      c.commitment.TimeboxSecs,
			DeadlineUnixSecs: c.deadline.Unix(),
		}
	}
	return st
}

func (c *Controller) persistLocked() error {
	snap := store.Snapshot{RuntimeState: c.runtimeState, Commitment: c.commitment}
	if !c.deadline.IsZero() {
		snap.DeadlineUnixSecs = c.deadline.Unix()
	}
	return store.Save(c.snapshotPath, snap)
}

// EnterPlanning moves Locked -> Planning.
func (c *Controller) EnterPlanning() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	next, err := statemachine.TransitionRuntime(c.runtimeState, statemachine.EnterPlanning)
	if err != nil {
		return err
	}
	c.runtimeState = next
	return c.persistLocked()
}

// StartManualCommitment validates input, activates a new commitment, and moves
// Planning -> Active.
func (c *Controller) StartManualCommitment(nextAction, successCondition string, timebox time.Duration) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	commitment, err := domain.NewManual(nextAction, successCondition, timebox)
	if err != nil {
		return err
	}
	commitment.State, err = statemachine.TransitionCommitment(commitment.State, statemachine.CommitmentActivate)
	if err != nil {
		return err
	}
	next, err := statemachine.TransitionRuntime(c.runtimeState, statemachine.ActivateAccepted)
	if err != nil {
		return err
	}
	c.runtimeState = next
	c.commitment = &commitment
	c.deadline = time.Now().Add(timebox)
	return c.persistLocked()
}

// Complete moves Active -> Review and marks the commitment completed.
func (c *Controller) Complete() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	next, err := statemachine.TransitionRuntime(c.runtimeState, statemachine.CompleteForReview)
	if err != nil {
		return err
	}
	c.runtimeState = next
	if c.commitment != nil {
		if s, e := statemachine.TransitionCommitment(c.commitment.State, statemachine.Complete); e == nil {
			c.commitment.State = s
		}
	}
	return c.persistLocked()
}

// End moves Review -> Locked and clears the commitment.
func (c *Controller) End() error {
	c.mu.Lock()
	defer c.mu.Unlock()
	next, err := statemachine.TransitionRuntime(c.runtimeState, statemachine.EndWorkPeriod)
	if err != nil {
		return err
	}
	c.runtimeState = next
	c.commitment = nil
	c.deadline = time.Time{}
	return c.persistLocked()
}