package coordinator

import (
	"errors"

	"chat-agent-system/internal/intent"
)

var (
	ErrNilContext    = errors.New("coordinator: nil user project context")
	ErrStaleContext  = errors.New("coordinator: stale context version")
	ErrInvalidUpdate = errors.New("coordinator: empty context update")
)

// ContextUpdate is the only typed write against UserProjectContext.
// Callers must supply ExpectedVersion from a prior read; a mismatch fails closed.
type ContextUpdate struct {
	ExpectedVersion int64

	BlackboardFill map[string]string
	BlackboardSet  map[string]string

	SetPendingExpectation bool
	PendingExpectation    *intent.PendingExpectation
	ExpirePending         bool

	SetInteractiveCard bool
	InteractiveCard    *intent.InteractiveCardPayload
	TickInteractive    bool
	DismissCardStatus  string // cancelled | resolved | expired; then nil

	SetPersonalizedGuidance bool
	PersonalizedGuidance    string

	SetRecentDialogue bool
	RecentDialogue    []DialogueTurn

	ProjectIDIfEmpty string
}

// ApplyContextUpdate applies one versioned patch. Concurrent writers with the
// same ExpectedVersion: exactly one succeeds, the rest get ErrStaleContext.
func ApplyContextUpdate(ctx *UserProjectContext, u ContextUpdate) error {
	if ctx == nil {
		return ErrNilContext
	}
	ctx.mu.Lock()
	defer ctx.mu.Unlock()
	if u.ExpectedVersion != ctx.Version {
		return ErrStaleContext
	}
	applied := false
	if len(u.BlackboardFill) > 0 {
		if ctx.BlackboardFacts == nil {
			ctx.BlackboardFacts = make(map[string]string, len(u.BlackboardFill))
		}
		for k, v := range u.BlackboardFill {
			if _, exists := ctx.BlackboardFacts[k]; !exists {
				ctx.BlackboardFacts[k] = v
			}
		}
		applied = true
	}
	if len(u.BlackboardSet) > 0 {
		if ctx.BlackboardFacts == nil {
			ctx.BlackboardFacts = make(map[string]string, len(u.BlackboardSet))
		}
		for k, v := range u.BlackboardSet {
			ctx.BlackboardFacts[k] = v
		}
		applied = true
	}
	if u.ExpirePending && ctx.PendingExpectation != nil && !ctx.PendingExpectation.ExpiresAt.IsZero() {
		// caller decides freshness; apply just clears
		ctx.PendingExpectation = nil
		applied = true
	}
	if u.SetPendingExpectation {
		ctx.PendingExpectation = u.PendingExpectation
		applied = true
	}
	if u.TickInteractive && ctx.InteractiveCard != nil {
		ctx.InteractiveCard.TTLTurns--
		if ctx.InteractiveCard.TTLTurns <= 0 || ctx.InteractiveCard.CurrentStatus != "active" {
			ctx.InteractiveCard.CurrentStatus = "expired"
			ctx.InteractiveCard = nil
		}
		applied = true
	}
	if u.DismissCardStatus != "" && ctx.InteractiveCard != nil {
		ctx.InteractiveCard.CurrentStatus = u.DismissCardStatus
		ctx.InteractiveCard = nil
		applied = true
	}
	if u.SetInteractiveCard {
		ctx.InteractiveCard = u.InteractiveCard
		applied = true
	}
	if u.SetPersonalizedGuidance {
		ctx.PersonalizedGuidance = u.PersonalizedGuidance
		applied = true
	}
	if u.SetRecentDialogue {
		ctx.RecentDialogue = u.RecentDialogue
		applied = true
	}
	if u.ProjectIDIfEmpty != "" && ctx.Project.ID == "" {
		ctx.Project.ID = u.ProjectIDIfEmpty
		applied = true
	}
	if !applied {
		return ErrInvalidUpdate
	}
	ctx.Version++
	return nil
}

func (c *UserProjectContext) applyPending(exp *intent.PendingExpectation) {
	if c == nil {
		return
	}
	_ = ApplyContextUpdate(c, ContextUpdate{ExpectedVersion: c.Version, SetPendingExpectation: true, PendingExpectation: exp})
}

func (c *UserProjectContext) applyCard(card *intent.InteractiveCardPayload) {
	if c == nil {
		return
	}
	_ = ApplyContextUpdate(c, ContextUpdate{ExpectedVersion: c.Version, SetInteractiveCard: true, InteractiveCard: card})
}

func (c *UserProjectContext) dismissCard(status string) {
	if c == nil {
		return
	}
	_ = ApplyContextUpdate(c, ContextUpdate{ExpectedVersion: c.Version, DismissCardStatus: status})
}

func (c *UserProjectContext) applyBlackboard(key, value string) {
	if c == nil {
		return
	}
	_ = ApplyContextUpdate(c, ContextUpdate{ExpectedVersion: c.Version, BlackboardSet: map[string]string{key: value}})
}