package capacity

import (
	"context"
	"math"
	"strconv"
	"strings"
)

// RecallItem is one recalled memory hit handed to the decider for L4 habit
// alignment (design §2.2 L4). It is a decoupling view over memory.Result so the
// capacity package stays independent of the memory subsystem; the loop builds it
// from Retriever.Retrieve. Scope carries the memory scope value ("user" / "persona"
// / "project") so L4 can honor the isolation red line (学行为习惯, 不读陌生人敏感).
type RecallItem struct {
	Content string
	Scope   string
	Kind    string
	Tags    []string
	Score   float64
}

// Judgment is the intent outcome of one round, meant to be written back into
// memory so the L4 layer learns the user's task-expression habits over time
// (design §2.4 闭环学习). It records the raw intent-layer classification (before
// any persona override) because the closed loop learns the user's intent pattern,
// not the persona's presentation. Text is the user expression that was judged — the
// habit key L4 re-matches on later rounds.
type Judgment struct {
	IsTask     bool
	TaskKind   string
	State      State
	Confidence float64
	Text       string
}

// L4 tuning constants.
const (
	// minHabitOverlap is the minimum longest-common-substring length (in runes) a
	// recalled habit must share with the current turn before L4 treats it as a
	// matching habit. 3 runes covers a short Chinese phrase (搞一下) while staying
	// conservative against token noise.
	minHabitOverlap = 3

	// taskHabitConfidence is the wake confidence L4 assigns when it matches a
	// habit-style memory (not a canonical intent record) that leans 办事. It sits
	// above the default wake threshold so the habit can actually wake a missed task.
	taskHabitConfidence = 0.7

	// intent kind tokens stored in an intent record and understood by awakenVerdict.
	taskKindComplex = "complex"
	taskKindCode    = "code"
	taskKindQuery   = "query"
	taskKindOps     = "ops"

	// intentRecordPrefix marks a canonical intent record written back by RecordIntent.
	intentRecordPrefix = "intent:"
)

// Judge 只跑意图分层（L1 → L2 → L3 → L4），返回该轮的原始判定
// （design §2.4 闭环学习的写回对象）：它不施加人格覆盖、不产出事件、
// 不改动任何状态，也不写任何东西。
//
// 它是 Decide 的「只看判定」视图：回合落定时调它一次即可拿到该轮判定
// 用于回写记忆（RecordIntent），既不必重跑整次决策，也不会重复触发
// capacity_awaken 广播。判定层被禁用或没有可判文本时返回零值
// （IsTask=false），调用方据此跳过写入。
func (d *Decider) Judge(ctx context.Context, in Input) Judgment {
	if !d.cfg.Enabled || len(in.Messages) == 0 {
		return Judgment{}
	}
	state, conf, tool := d.intent(ctx, in)
	return judgmentFor(in, state, conf, tool)
}

// IsIntentRecord 报告 content 是否为 RecordIntent 写回的规范意图记录
// （design §2.4）。群聊/陌生人的记忆注入据此把主人原话的机器可读形态
// 挡在只读共享块之外：那是 L4 的学习素材与「主人敏感信息」，
// 不是给群聊消费的非敏感共享记忆。
func IsIntentRecord(content string) bool {
	_, ok := parseIntentRecord(content)
	return ok
}

// RecordIntent formats a judgment into the canonical intent-record string written
// back to memory (design §2.4). Only task judgments are worth learning — a quiet /
// non-task judgment returns "" so callers can skip persisting noise. The format is
// machine-parseable by parseIntentRecord, which L4 re-reads on later rounds to
// close the learning loop. The user expression is written in plain text so the
// keyword retriever can still surface it against a later similar turn.
func (d *Decider) RecordIntent(j Judgment) string {
	if !j.IsTask {
		return ""
	}
	return formatIntentRecord(j)
}

// formatIntentRecord encodes j as one parseable line. The text field comes last and
// is taken verbatim (it may contain ';' or '='), so parseIntentRecord reads the
// fixed prefix and keeps the remainder as the expression.
func formatIntentRecord(j Judgment) string {
	return intentRecordPrefix +
		"isTask=" + strconv.FormatBool(j.IsTask) +
		";taskKind=" + j.TaskKind +
		";confidence=" + strconv.FormatFloat(j.Confidence, 'f', -1, 64) +
		";text=" + j.Text
}

// intentRecord is the parsed form of a canonical intent record.
type intentRecord struct {
	isTask     bool
	taskKind   string
	confidence float64
	text       string
}

// parseIntentRecord decodes a canonical intent record written by formatIntentRecord.
// ok is false when content is not a well-formed intent record (missing isTask).
func parseIntentRecord(content string) (intentRecord, bool) {
	rest, ok := strings.CutPrefix(content, intentRecordPrefix)
	if !ok {
		return intentRecord{}, false
	}
	// text is last and taken verbatim, so a ';' or '=' inside it cannot split it.
	head, text := rest, ""
	if idx := strings.Index(rest, ";text="); idx >= 0 {
		head = rest[:idx]
		text = rest[idx+len(";text="):]
	}
	rec := intentRecord{text: text}
	seenTask := false
	for _, f := range strings.Split(head, ";") {
		k, v, cut := strings.Cut(f, "=")
		if !cut {
			continue
		}
		switch k {
		case "isTask":
			rec.isTask = v == "true"
			seenTask = true
		case "taskKind":
			rec.taskKind = v
		case "confidence":
			if x, err := strconv.ParseFloat(v, 64); err == nil {
				rec.confidence = x
			}
		}
	}
	if !seenTask {
		return intentRecord{}, false
	}
	return rec, true
}

// l4 is the L4 habit-alignment layer (design §2.2, §2.4): it uses recalled user
// habits to correct or fill in the intent that L1/L2 could not settle. It returns
// ok=false when no habit applies, so the caller's L1/L2 verdict (or the
// conservative fallback) stands — L4 is silent unless a learned habit matches
// (向后兼容, 数据缺失时回退).
func (d *Decider) l4(current string, recall []RecallItem) (State, float64, string, bool) {
	text := strings.TrimSpace(current)
	if text == "" || len(recall) == 0 {
		return "", 0, "", false
	}
	bestState, bestConf, bestTool := State(""), 0.0, ""
	matched := false
	for _, it := range recall {
		if !allowedHabitScope(it.Scope) {
			continue
		}
		if rec, ok := parseIntentRecord(it.Content); ok {
			// A canonical record written back by RecordIntent: it knows the exact
			// task kind and confidence. Only a task record with a matching expression
			// testifies to task; the stored text is plaintext so overlap is matched
			// against it (tolerating paraphrase).
			if !rec.isTask || rec.text == "" || overlapLen(text, rec.text) < minHabitOverlap {
				continue
			}
			state, tool := awakenVerdict(rec.taskKind)
			conf := clampConf(rec.confidence)
			if conf == 0 {
				conf = taskHabitConfidence
			}
			if conf > bestConf {
				bestState, bestConf, bestTool, matched = state, conf, tool, true
			}
			continue
		}
		// Habit-style memory (not written by us): treat it as a task habit only when
		// it leans 办事 and shares a phrase with the current turn, so an unrelated
		// preference (coffee habit) never triggers a wake.
		if !leansTask(it.Content) || overlapLen(text, it.Content) < minHabitOverlap {
			continue
		}
		conf := taskHabitConfidence
		if it.Score > 0 {
			conf = clampConf(taskHabitConfidence + it.Score*0.15)
		}
		state, tool := StateAwake, inferTool(text)
		if isComplex(text) {
			state = StateFull
		}
		if conf > bestConf {
			bestState, bestConf, bestTool, matched = state, conf, tool, true
		}
	}
	if !matched {
		return "", 0, "", false
	}
	return bestState, bestConf, bestTool, true
}

// mergeL4 combines an L1/L2 verdict with the L4 habit verdict (design §2.2 合并规则).
// It is conservative: a strong learned habit may count a task the heuristics missed
// (quiet → awake, a 举手示意 but never a jump straight to full) or confirm/boost one
// they caught, up to full when the habit says complex; it never drags a clear task
// down to quiet (学行为习惯，不误打断).
func (d *Decider) mergeL4(s State, c float64, t string, l4s State, l4c float64, l4t string, l4ok bool) (State, float64, string) {
	if !l4ok || (l4s != StateAwake && l4s != StateFull) {
		return s, c, t
	}
	if s == StateQuiet || s == "" {
		// 保守红线：静息→唤醒是"举手示意"，即便习惯标记复杂也不直接跳到全能。
		return StateAwake, l4c, l4t
	}
	st := s
	if l4s == StateFull {
		st = StateFull
	}
	return st, boostConf(c, l4c), pickTool(t, l4t)
}

// awakenVerdict maps an intent-record task kind back to a state + lit tool.
func awakenVerdict(kind string) (State, string) {
	switch kind {
	case taskKindComplex:
		return StateFull, ""
	case taskKindCode:
		return StateAwake, "file"
	case taskKindQuery:
		return StateAwake, "web-search"
	case taskKindOps:
		return StateAwake, "terminal"
	default:
		return StateAwake, ""
	}
}

// taskKindFor maps a (state, tool) to the intent kind recorded for writeback.
func taskKindFor(state State, tool string) string {
	if state == StateFull {
		return taskKindComplex
	}
	switch tool {
	case "file":
		return taskKindCode
	case "web-search", "web-fetch", "http":
		return taskKindQuery
	case "terminal":
		return taskKindOps
	default:
		return ""
	}
}

// allowedHabitScope reports the scopes L4 may read for user habits. ScopeUser is the
// owner's shared habit (primary); ScopePersona / ScopeProject are readable per design
// §2.2; an empty scope (recall without scope metadata) is tolerated. Any other scope
// is refused, so a stranger / owner-private memory can never reach L4 here (design
// §2.2 红线: 学行为习惯, 不读陌生人敏感).
func allowedHabitScope(scope string) bool {
	switch scope {
	case "", "user", "persona", "project":
		return true
	default:
		return false
	}
}

// leansTask reports whether a habit memory is about the user's task-expression
// pattern rather than an unrelated preference, so L4 does not wake on a coffee habit.
func leansTask(content string) bool {
	return containsAny(content, []string{
		"办事", "任务", "布置", "要办", "让我", "要我", "去做", "来办", "干活", "做工",
		"习惯用", "习惯说", "让我做", "叫我",
		// ASCII
		"task", "asks me to", "want me to", "has me", "habit",
	})
}

// overlapLen returns the length (in runes) of the longest common substring of a and
// b — the lexical-overlap measure L4 uses to detect "the user expression this round
// echoes a phrase the memory recorded", tolerating paraphrase (搞一下那个部署 vs
// 搞一下这个部署 share 搞一下).
func overlapLen(a, b string) int {
	ar, br := []rune(a), []rune(b)
	if len(ar) == 0 || len(br) == 0 {
		return 0
	}
	prev := make([]int, len(br)+1)
	best := 0
	for i := 1; i <= len(ar); i++ {
		cur := make([]int, len(br)+1)
		for j := 1; j <= len(br); j++ {
			if ar[i-1] == br[j-1] {
				cur[j] = prev[j-1] + 1
				if cur[j] > best {
					best = cur[j]
				}
			}
		}
		prev = cur
	}
	return best
}

// boostConf raises a confirmed task confidence above the stronger of the two sources,
// reflecting corroboration (设计: 越用越准), capped at 1.
func boostConf(a, b float64) float64 { return clampConf(math.Max(a, b) + 0.05) }

// clampConf clamps c to [0,1].
func clampConf(c float64) float64 {
	if c < 0 {
		return 0
	}
	if c > 1 {
		return 1
	}
	return c
}

// pickTool prefers the learned habit's lit tool when non-empty, else the caller's.
func pickTool(t, l4t string) string {
	if l4t != "" {
		return l4t
	}
	return t
}

// judgmentFor builds the write-back judgment from the raw intent-layer result.
func judgmentFor(in Input, state State, conf float64, tool string) Judgment {
	j := Judgment{State: state, Confidence: conf}
	if n := len(in.Messages); n > 0 {
		j.Text = in.Messages[n-1]
	}
	j.IsTask = state == StateAwake || state == StateFull
	if j.IsTask {
		j.TaskKind = taskKindFor(state, tool)
	}
	return j
}