package loop

import (
	"context"
	"strings"

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

// This file owns the speaker attribution of the model context (DevDocs/design/22
// §7-5). A process now hosts several roles at once and a session keeps its
// conversation when its role is switched, so the model must be able to tell which
// utterances in the context came from which role: the assistant messages of a
// previous role must not read as "something I said", and the role answering now
// must recognize itself.
//
// Two hard rules shape the rendering:
//   - The attributed metadata never enters a message body. A user message is
//     free text from the outside world, so letting it carry system-looking markup
//     would hand whoever writes it a chance to impersonate a system instruction
//     (design/11 §10). Attribution therefore travels as its own system messages,
//     never as a prefix inside user or assistant text.
//   - The rendering only ADDS system messages. It never reorders, rewrites or
//     drops a message, so the assembled prompt keeps its established shape: the
//     agent's instructions stay the first system message and the time / working
//     memory / memory blocks keep their existing order (assembleContext owns the
//     placement; this file only supplies the extra segment).
//
// The per-message speaker is read from the structured model.Message.SenderName
// lane, because model/** is frozen in this batch and a Message has no dedicated
// persona field. Only assistant messages are read: for an assistant turn the
// sender IS the role that spoke it, while a labelled user message keeps its
// pre-existing meaning (the third-party sender marker of design/16 §4.6), which
// this file deliberately leaves alone.

// Attribution markers. Both are compile-time constants so no magic string
// appears in the run path and a test can assert the exact wire shape.
const (
	// roleContextMarker opens the leading segment that declares the speaking role.
	roleContextMarker = "[会话角色] "
	// speakerSwitchMarker opens a boundary note inserted where the speaker of the
	// conversation changes.
	speakerSwitchMarker = "[发言归属] "
)

// speakerOf returns the role id labelled as the speaker of m, or "" when the
// message carries no attribution. Only assistant messages are considered: a user
// message's SenderName is the third-party display name lane of design/16 §4.6 and
// has nothing to do with persona selection.
func speakerOf(m model.Message) string {
	if m.Role != model.RoleAssistant {
		return ""
	}
	return strings.TrimSpace(m.SenderName)
}

// anySpeakerLabel reports whether any message of the conversation carries a
// speaker label. When none does, attribution rendering is a complete no-op: a
// single-role conversation (or a caller that never labels its messages) keeps the
// exact pre-multi-character prompt it had before.
func anySpeakerLabel(msgs []model.Message) bool {
	for _, m := range msgs {
		if speakerOf(m) != "" {
			return true
		}
	}
	return false
}

// attributeConversation renders the role context for one model step. It returns
// the leading role declaration (ok = false when the conversation carries no
// speaker label at all), and the conversation with a boundary note inserted
// wherever the labelled speaker changes.
//
// The note announces the speaker for every labelled message that follows it until
// the next note, which is exactly the granularity the model needs to answer "第 N
// 条是谁说的" without touching a single message body. Rendering happens at request
// build time from the live slice, so a window that was truncated or compacted in
// the meantime can never end up with a message under the wrong speaker: a dropped
// note is regenerated, and no note claims a position it does not have.
func (l *Loop) attributeConversation(ctx context.Context, msgs []model.Message) (model.Message, bool, []model.Message) {
	if !anySpeakerLabel(msgs) {
		return model.Message{}, false, msgs
	}
	current := l.personaFor(ctx)
	out := make([]model.Message, 0, len(msgs)+2)
	prev := ""
	for _, m := range msgs {
		if s := speakerOf(m); s != "" && s != prev {
			out = append(out, model.TextMessage(model.RoleSystem, l.speakerSwitchText(s, current)))
			prev = s
		}
		out = append(out, m)
	}
	return l.roleContextMessage(current), true, out
}

// roleContextMessage builds the leading segment that declares which role is
// answering, so a role that was just switched in has a strong sense of its own
// identity on top of its instructions (design/22 §7-5). It states the boundary
// rule for the notes below: an attributed utterance belongs to the role it was
// labelled with, not to the role answering now.
func (l *Loop) roleContextMessage(current string) model.Message {
	var b strings.Builder
	b.WriteString(roleContextMarker)
	if current != "" {
		b.WriteString("你正以")
		b.WriteString(l.speakerLabel(current))
		b.WriteString("的身份对话。")
	}
	b.WriteString("本会话此前由不同角色相继发言：下面凡是标了「发言归属」的发言，都只属于标注的那个角色——" +
		"不要把别个角色说过的话当成你自己说过的，也不要继承他们的身份、口吻或立场；" +
		"该标注从其出现处起生效，直到下一条「发言归属」为止。")
	return model.TextMessage(model.RoleSystem, b.String())
}

// speakerSwitchText builds the boundary note for one speaking role. A stretch of
// the answering role's own history is stated as "来自你自己" (so the model keeps
// continuity with what it said before a switch), every other role is stated as
// belonging to that role and explicitly not to the answering one.
func (l *Loop) speakerSwitchText(personaID, current string) string {
	label := l.speakerLabel(personaID)
	if personaID != "" && personaID == current {
		return speakerSwitchMarker + "以下发言来自你自己——" + label + "。"
	}
	return speakerSwitchMarker + "以下发言来自" + label + "，不是你说的。"
}

// speakerLabel renders a role reference for the model: the role's display name
// with its id when a name resolver knows the role, the id alone otherwise. It
// never returns an empty string, so a note always names someone.
func (l *Loop) speakerLabel(personaID string) string {
	name := ""
	if l.personaName != nil {
		name = strings.TrimSpace(l.personaName(personaID))
	}
	if name == "" || name == personaID {
		return "「" + personaID + "」"
	}
	return "「" + name + "」（" + personaID + "）"
}