package channelbridge

import (
	"context"
	"fmt"
	"strings"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/adapter"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/user"
)

// proactiveTarget is the owner's IM address (platform + account id) resolved for
// a proactive push. The account id doubles as the DM peer on every adapter.
type proactiveTarget struct {
	platform  string
	accountID string
}

// proactiveRecentCount is how many of the most recent main-session messages the
// proactive target selection scans to find "where the owner last talked", so a
// push lands on the channel she is actually using. Compile-time so no magic number
// appears in the run path.
const proactiveRecentCount = 20

// SendProactive pushes msg to the owner's IM channel via the registered adapter
// for that platform. It is the backthink IMAdapter seam (design/12 §3 fallback) and
// delivers to exactly ONE owner channel, chosen by the single-target selection in
// proactiveTarget: her explicit [渠道:...] choice first, then the platform she last
// used, then the whitelist default (rotating so it is not always the same channel).
// WeChat is a first-class candidate (it is whitelisted and, when connected, the
// recent-active/fallback selection may pick it).
//
// The push exits through the shared IM bubble dispatcher (sendIMBubbles), so a
// multi-paragraph message is split into bubbles, role-play/narration is stripped, and
// sends are spaced 0.5-2s apart — the same behaviour as a reply, and the reason
// WeChat/other IM proactive pushes no longer arrive as one un-split <p> blob.
//
// When the owner profile has no whitelisted account that is backed by a connected
// adapter it returns a clear error so the caller records the reason rather than
// silently dropping the push.
func (b *Bridge) SendProactive(ctx context.Context, msg adapter.UnifiedMessage) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	target, ok := b.proactiveTarget(ctx, msg)
	if !ok {
		return fmt.Errorf("channelbridge: no connected owner IM channel for proactive push")
	}
	ad := b.adapterForPlatform(target.platform)
	if ad == nil {
		return fmt.Errorf("channelbridge: no adapter for owner platform %q", target.platform)
	}
	out := msg
	out.Platform = target.platform
	out.ChannelType = adapter.ChannelDirect
	// The owner's account id is the DM peer on every adapter: telegram/qq read
	// ChannelID, kook/weixin read SenderID (with ChannelID as the fallback). Setting
	// both keeps a direct message targetable regardless of which field the adapter
	// prefers, without duplicating the message.
	out.ChannelID = target.accountID
	out.SenderID = target.accountID
	// The push exits through the shared IM bubble dispatcher, so a multi-paragraph
	// proactive message is split into bubbles and role-play/narration is stripped, with
	// the same 0.5-2s gap as a reply — WeChat proactive pushes are no longer sent as a
	// single un-split message.
	if err := b.sendIMBubbles(ctx, out, func(ctx context.Context, msg adapter.UnifiedMessage) error {
		return ad.SendProactive(ctx, msg)
	}, msg.Content); err != nil {
		return fmt.Errorf("channelbridge: send proactive via %q: %w", target.platform, err)
	}
	// Mirror the proactive message into the main conversation context (design/16
	// §4.4 + §4.6.1). Without this the model would not see what it proactively said, so
	// a follow-up owner reply would feel incoherent (the message "loses" its history).
	// It is the same mirror path as owner-private IM replies, scoped to MainSessionID.
	b.persistToMain(ctx, history.RoleAssistant, msg.Content, target.platform,
		fmt.Sprintf("%s:%s:%s", target.platform, target.accountID, target.accountID),
		target.platform)
	return nil
}

// proactiveTarget resolves the single owner account a proactive push should reach.
// The range is every whitelisted owner channel that is backed by a connected
// adapter (WeChat included), and the choice follows the backthink priority:
//
//  1. A concrete msg.Platform (her [渠道:...] choice) that is whitelisted AND
//     connected selects that channel.
//  2. The channel she most recently used in the main session (an owner/dialog
//     message on a whitelisted, connected platform) is preferred.
//  3. Otherwise the platform that the whitelist default selects, rotating from a
//     cursor so the fallback is not always the same channel (e.g. always kook).
//
// A nil owner or an empty whitelist yields !ok, as does a whitelist with no
// connected adapter.
func (b *Bridge) proactiveTarget(ctx context.Context, msg adapter.UnifiedMessage) (proactiveTarget, bool) {
	accounts := b.ownerAccounts()
	if len(accounts) == 0 {
		return proactiveTarget{}, false
	}

	platform := strings.ToLower(strings.TrimSpace(msg.Platform))
	if !isGenericProactivePlatform(platform) {
		if acct, ok := matchOwnerAccount(accounts, platform); ok && b.hasConnectedAdapter(acct.Platform) {
			return proactiveTarget{acct.Platform, acct.AccountID}, true
		}
	}

	if acct, ok := b.recentActiveAccount(ctx, accounts); ok {
		return proactiveTarget{acct.Platform, acct.AccountID}, true
	}

	if acct, ok := b.nextConnectedAccount(accounts); ok {
		return proactiveTarget{acct.Platform, acct.AccountID}, true
	}

	return proactiveTarget{}, false
}

// ownerAccounts returns the owner's whitelisted accounts that carry an account id,
// in whitelist order. A nil owner or an empty whitelist yields nil.
func (b *Bridge) ownerAccounts() []user.OwnerAccount {
	if b.owner == nil {
		return nil
	}
	out := make([]user.OwnerAccount, 0, len(b.owner.Accounts))
	for _, a := range b.owner.Accounts {
		if a.AccountID != "" {
			out = append(out, a)
		}
	}
	if len(out) == 0 {
		return nil
	}
	return out
}

// matchOwnerAccount returns the owner account whose platform equals platform,
// case-insensitively.
func matchOwnerAccount(accounts []user.OwnerAccount, platform string) (user.OwnerAccount, bool) {
	for _, a := range accounts {
		if strings.EqualFold(a.Platform, platform) {
			return a, true
		}
	}
	return user.OwnerAccount{}, false
}

// recentActiveAccount returns the owner account for the most recent main-session
// message whose platform is a whitelisted, connected owner channel — the "she is
// active there" signal. A nil history store, a failed read or an empty tail yields
// ok=false so selection falls through to the default rather than guessing.
func (b *Bridge) recentActiveAccount(ctx context.Context, accounts []user.OwnerAccount) (user.OwnerAccount, bool) {
	if b.history == nil {
		return user.OwnerAccount{}, false
	}
	recent, err := b.history.Recent(ctx, history.MainSessionID, proactiveRecentCount)
	if err != nil || len(recent) == 0 {
		return user.OwnerAccount{}, false
	}
	// Recent is oldest-first; walk newest-first so the most recent channel wins.
	for i := len(recent) - 1; i >= 0; i-- {
		p := strings.ToLower(strings.TrimSpace(recent[i].Platform))
		if p == "" || isGenericProactivePlatform(p) {
			continue
		}
		if acct, ok := matchOwnerAccount(accounts, p); ok && b.hasConnectedAdapter(acct.Platform) {
			return acct, true
		}
	}
	return user.OwnerAccount{}, false
}

// nextConnectedAccount returns the next whitelisted owner account with a connected
// adapter, advancing a cursor so the no-signal fallback rotates instead of always
// landing on the first whitelisted channel (e.g. always kook). It holds the bridge
// lock to read the adapter map and update the cursor atomically.
func (b *Bridge) nextConnectedAccount(accounts []user.OwnerAccount) (user.OwnerAccount, bool) {
	b.mu.Lock()
	defer b.mu.Unlock()
	n := len(accounts)
	for i := 0; i < n; i++ {
		idx := (b.proactiveCursor + i) % n
		a := accounts[idx]
		if b.hasConnectedAdapterLocked(a.Platform) {
			b.proactiveCursor = (idx + 1) % n
			return a, true
		}
	}
	return user.OwnerAccount{}, false
}

// hasConnectedAdapter reports whether a registered adapter with this base platform
// is currently connected, so a channel is only ever selected when it can actually
// deliver a message.
func (b *Bridge) hasConnectedAdapter(platform string) bool {
	b.mu.RLock()
	defer b.mu.RUnlock()
	return b.hasConnectedAdapterLocked(platform)
}

// hasConnectedAdapterLocked is hasConnectedAdapter without taking the lock; the
// caller must hold b.mu (read or write).
func (b *Bridge) hasConnectedAdapterLocked(platform string) bool {
	for name, a := range b.adapters {
		if strings.EqualFold(basePlatform(name), platform) && a.IsConnected() {
			return true
		}
	}
	return false
}

// isGenericProactivePlatform reports whether platform is a routing keyword rather
// than a concrete channel id. Only these fall through to the recent-active / default
// selection; a concrete id must resolve to a whitelisted, connected channel before
// it is honored, so an explicit channel choice is never silently replaced by a
// different channel.
func isGenericProactivePlatform(platform string) bool {
	switch platform {
	case "", "cyrene-backthink":
		return true
	default:
		return false
	}
}

// adapterForPlatform returns a registered adapter whose base platform matches
// platform (multi-account names like "kook:3be..." resolve to their bare base),
// preferring a connected one so a dead account is only tried when it is the only
// option. It returns nil when none is registered.
func (b *Bridge) adapterForPlatform(platform string) adapter.PlatformAdapter {
	b.mu.RLock()
	defer b.mu.RUnlock()
	var first adapter.PlatformAdapter
	for name, a := range b.adapters {
		if !strings.EqualFold(basePlatform(name), platform) {
			continue
		}
		if a.IsConnected() {
			return a
		}
		if first == nil {
			first = a
		}
	}
	return first
}