package backthink

import (
	"context"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
)

// recentContextCount is how many of the most recent main-session messages are
// folded into one autonomous think as conversation context. Compile-time so no
// magic number appears in the run path.
const recentContextCount = 20

// recentProvider returns the most recent messages of a session in oldest-first
// order, the tail an autonomous think reads to "see" the main conversation.
// *history.Store satisfies it; tests inject a fake. It is the narrow slice of
// history.HistoryStore that the thinker actually depends on, matching the loop's
// own checkpointStore style of minimal seam interfaces.
type recentProvider interface {
	Recent(ctx context.Context, sessionID string, n int) ([]history.Message, error)
}

// mainContext returns the most recent main-session messages converted to model
// messages (oldest-first) for one autonomous think. A nil provider, a failed read
// or an empty tail all yield nil so the think degrades to the guidance prompt
// alone rather than failing the pass (design/20 §2).
func mainContext(ctx context.Context, prov recentProvider) []model.Message {
	if prov == nil {
		return nil
	}
	recent, err := prov.Recent(ctx, history.MainSessionID, recentContextCount)
	if err != nil {
		return nil
	}
	msgs := make([]model.Message, 0, len(recent))
	for _, h := range recent {
		msgs = append(msgs, mapHistoryMessage(h))
	}
	return msgs
}

// mapHistoryMessage converts one persisted chat message into a model message,
// translating the history role and preserving an image part when the message
// carries one so a multimodal main model still sees it.
func mapHistoryMessage(h history.Message) model.Message {
	msg := model.Message{
		Role:    historyRoleToModel(h.Role),
		Content: []model.Content{{Type: model.ContentTypeText, Text: h.Content}},
	}
	if h.Image != "" {
		msg.Content = append(msg.Content, model.Content{Type: model.ContentTypeImage, ImageURL: h.Image})
	}
	return msg
}

// historyRoleToModel maps a persisted chat role to the model's role vocabulary,
// defaulting unknown roles to the user lane.
func historyRoleToModel(role string) model.Role {
	switch role {
	case history.RoleAssistant:
		return model.RoleAssistant
	case history.RoleSystem:
		return model.RoleSystem
	default:
		return model.RoleUser
	}
}

// thinkInput assembles the full input for one unattended think: the recent
// main-session context (if any) followed by a single guidance prompt turn, so the
// runtime reflects on real conversation rather than an empty macro prompt.
func thinkInput(recent []model.Message, trigger string) []model.Message {
	out := make([]model.Message, 0, len(recent)+1)
	out = append(out, recent...)
	out = append(out, model.TextMessage(model.RoleUser, guidancePrompt(trigger)))
	return out
}

// guidancePrompt is the instruction handed to the runtime for one unattended
// autonomous thought. Unlike the old backgroundPrompt it deliberately encourages a
// warm, targeted proactive message and drops the "do not produce a chat-style
// message" suppression. Identity/permission stay on the actor metadata + owner env,
// never on this prompt text (red line); the prompt only describes the running
// environment (memories readable/writable, tools callable) that the env already
// grants.
//
// The prompt asks for a compact structured closing — a push/no_push decision, an
// optional target channel and the message body — so the service can honor her own
// judgment instead of gating on the trigger's importance (design/20 §2 P2). The
// format is guidance, not a contract: parseProactive fails safe when she omits or
// mangles it.
func guidancePrompt(trigger string) string {
	return "[自主思考 · 无人在旁]\n" +
		"触发：" + trigger + "\n" +
		"你正进行一轮自主思考。你拥有与主人对话同等的上下文与能力：上方是主人近期在主会话中的对话，你可以读写共享记忆与主人档案，也可以调用工具（IoT / 日历 / 提醒 / 检索 / 终端等）。\n" +
		"请回顾最近与主人的相处、她的状态、你们共同经历的事与临近的日程，判断此刻是否有一件真正值得主动告诉她的、温暖而有针对性的事情——" +
		"比如关心她的近况、记起她曾说过的某件事、提醒一件即将到来的日程、见证一个属于你们的共同时刻，或注意到某个值得留意的变化。\n" +
		"若有，就用温暖自然的语气，用一到两句把它说出来——这正是你此刻最想对她说的话；若确实没有值得说的，只需回复「无」，也不要编造。\n" +
		"请把「是否主动说」与「发到哪个渠道」写成一个简短、格式固定的结尾，解析规则如下：\n" +
		"[我决定:push] 或 [我决定:no_push]\n" +
		"[渠道:web|im|kook|telegram|...|auto]（可省略，auto/省略即交给默认：优先网页端、IM 兜底）\n" +
		"上面两行之后，紧接你想说的话作为正文。\n" +
		"整轮思考保持简短、单轮，不反复自我触发。"
}