package intent

import (
	"context"
	"fmt"
	"math"
	"sort"
	"strings"
	"time"

	"logging-system/logsys"
)

// Recognizer 是识别的公开端口（Query 语义：纯函数式、无副作用）。
// error 只表示系统级失败（nil 快照、输入超长）；BranchFallback 是正常结果。
type Recognizer interface {
	Recognize(ctx context.Context, input string, snap *Snapshot) (Result, error)
}

// FunnelRecognizer 四级漏斗实现：guard → expectation → rules → adjudicate，
// 可选注入挂起预期提供者与 Ambiguous 分支的 L2 分类器。
// I2 的分层：歧义先经语义重排（确定性宿主打分）再到 L2 分类器（模型）。
type FunnelRecognizer struct {
	log *logsys.Logger
	exp ExpectationProvider
	cls Classifier
	sem SemanticScorer
	thr float64
	gen CommandGenerator
}

// NewRecognizer 构建漏斗识别器。opts 仅使用 Log 字段（阈值类参数在快照内）；
// exp / cls 可为 nil（对应阶段不启用）。语义与生成端口经 Options 注入（I2）。
func NewRecognizer(opts Options, exp ExpectationProvider, cls Classifier) *FunnelRecognizer {
	o := opts.normalized()
	return &FunnelRecognizer{log: o.Log, exp: exp, cls: cls,
		sem: o.Semantic, thr: o.SemanticThreshold, gen: o.Generator}
}

// Recognize 识别一次输入。确定性：同输入 + 同快照 → 同结果（日志中的耗时除外）。
func (r *FunnelRecognizer) Recognize(ctx context.Context, input string, snap *Snapshot) (Result, error) {
	if snap == nil {
		err := newError(InvalidArgument, "snapshot 为 nil")
		r.log.Module("intent").WithContext(ctx).Error("intent recognize rejected", err)
		return Result{}, err
	}
	if len(input) > snap.maxInput {
		err := newError(InvalidArgument, "输入超过长度上限", "actual_len", len(input), "max_len", snap.maxInput)
		r.log.Module("intent").WithContext(ctx).Error("intent recognize rejected", err)
		return Result{}, err
	}
	start := time.Now()
	res := r.recognize(ctx, input, snap)
	// 生成端口已经给出经过校验的命令列表时不再用规则展开覆盖（I2）。
	if res.Commands == nil {
		res.Commands = deriveCommands(res, snap)
	}
	topID, conf := "", 0.0
	if res.Top != nil {
		topID, conf = res.Top.ID, res.Top.Confidence
	}
	r.log.Module("intent").WithContext(ctx).Info("intent recognized",
		"branch", string(res.Branch),
		"top_id", topID,
		"confidence", conf,
		"snapshot_revision", res.SnapshotRevision,
		"duration_ms", time.Since(start).Milliseconds())
	return res, nil
}

func (r *FunnelRecognizer) recognize(ctx context.Context, input string, snap *Snapshot) Result {
	if strings.TrimSpace(input) == "" {
		return Result{Input: input, Branch: BranchFallback, SnapshotRevision: snap.rev}
	}
	// 否定只认 excludes_any 子串，不做语义否定；「不要写入」这类说法交给命令层 Cancel。
	matchInput, folded := snap.foldInput(input)

	// Stage 0：守卫命中即短路，可表达"识别即拒绝"。
	if guardHits := snap.evalGuard(matchInput, folded); len(guardHits) > 0 {
		cands := candidatesOf(trimHits(guardHits, snap.topN), input, true)
		top := cands[0]
		return Result{Input: input, Branch: BranchGuardHit, Top: &top, Candidates: cands, SnapshotRevision: snap.rev}
	}

	// Stage 1：会话挂起预期优先于一般规则（宿主可选注入）。
	if r.exp != nil {
		if pending := r.exp.Pending(ctx); pending != nil && len(pending.IntentIDs) > 0 {
			if hits := snap.evalIDs(pending.IntentIDs, matchInput, folded); len(hits) > 0 {
				cands := candidatesOf(trimHits(hits, snap.topN), input, true)
				top := cands[0]
				return Result{Input: input, Branch: BranchExpectationHit, Top: &top, Candidates: cands, SnapshotRevision: snap.rev}
			}
		}
	}

	// Stage 2 + 3：规则计分与置信度裁决。
	hits := snap.evalRules(matchInput, folded)
	switch {
	case len(hits) == 0:
		// I2：规则与语义都未命中时，可选经模型命令生成端口兜底（校验同款）。
		if r.gen != nil {
			if res, ok := r.generateCommands(ctx, input, snap); ok {
				return res
			}
		}
		return Result{Input: input, Branch: BranchFallback, SnapshotRevision: snap.rev}
	case len(hits) == 1 || hits[0].score-hits[1].score >= snap.margin || tieBreakByPriority(hits):
		cands := candidatesOf(trimHits(hits, snap.topN), input, true)
		top := cands[0]
		return Result{Input: input, Branch: BranchMatched, Top: &top, Candidates: cands, SnapshotRevision: snap.rev}
	}

	// Ambiguous：先语义重排（I2 确定性宿主打分），失败或不达阈才到 L2 分类器。
	cands := candidatesOf(trimHits(hits, snap.topN), input, false)
	if r.sem != nil {
		if top, ok := r.semanticRerank(ctx, input, cands, snap); ok {
			snap.fillTopSlots(&top, input)
			top.Reason = top.Reason + "; refined_by=semantic"
			return Result{Input: input, Branch: BranchMatched, Top: &top, Candidates: cands, SnapshotRevision: snap.rev}
		}
	}
	if r.cls != nil {
		refined, err := r.cls.Refine(ctx, input, cands)
		if err != nil {
			r.log.Module("intent").WithContext(ctx).Warn("intent classifier failed; keep ambiguous", "error", err.Error())
			return Result{Input: input, Branch: BranchAmbiguous, Candidates: cands, SnapshotRevision: snap.rev}
		}
		rebuilt, err := validateRefined(cands, refined)
		if err != nil {
			r.log.Module("intent").WithContext(ctx).Warn("intent classifier result rejected; keep ambiguous", "error", err.Error())
			return Result{Input: input, Branch: BranchAmbiguous, Candidates: cands, SnapshotRevision: snap.rev}
		}
		if top, ok := adjudicateRefined(rebuilt, snap); ok {
			snap.fillTopSlots(&top, input)
			top.Reason = top.Reason + "; refined_by=classifier"
			return Result{Input: input, Branch: BranchMatched, Top: &top, Candidates: rebuilt, SnapshotRevision: snap.rev}
		}
		cands = rebuilt
	}
	return Result{Input: input, Branch: BranchAmbiguous, Candidates: cands, SnapshotRevision: snap.rev}
}

// tieBreakByPriority 报告同分（分差为 0）且前两名 Priority 不同：
// 此时高 Priority 者直接胜出，不再标歧（I5）。分差小于 margin 但非零时
// 仍按 ambiguous 处理（margin 语义不变）。
func tieBreakByPriority(hits []specHit) bool {
	if len(hits) < 2 {
		return false
	}
	return hits[0].score == hits[1].score && hits[0].cs.spec.Priority > hits[1].cs.spec.Priority
}

// validateRefined 要求分类器返回与原候选完全相同的 ID 集合且无重复。
// 置信度必须是有限值并落在 [0,1]；越界判为不合法，不截断。
// 除 Confidence 外的字段一律按 ID 从原候选重建，分类器改写的 Handler 等不生效。
func validateRefined(original, refined []Candidate) ([]Candidate, error) {
	byID := make(map[string]Candidate, len(original))
	for _, c := range original {
		if _, dup := byID[c.ID]; dup {
			return nil, fmt.Errorf("duplicate original id %s", c.ID)
		}
		byID[c.ID] = c
	}
	if len(refined) != len(original) {
		return nil, fmt.Errorf("refined candidate count %d != %d", len(refined), len(original))
	}
	seen := make(map[string]struct{}, len(refined))
	out := make([]Candidate, len(refined))
	for i, got := range refined {
		if _, dup := seen[got.ID]; dup {
			return nil, fmt.Errorf("duplicate refined id %s", got.ID)
		}
		seen[got.ID] = struct{}{}
		src, ok := byID[got.ID]
		if !ok {
			return nil, fmt.Errorf("unknown refined id %s", got.ID)
		}
		if !validConfidence(got.Confidence) {
			return nil, fmt.Errorf("confidence out of range for %s", got.ID)
		}
		src.Confidence = got.Confidence
		out[i] = src
	}
	return out, nil
}

func validConfidence(v float64) bool {
	return !math.IsNaN(v) && !math.IsInf(v, 0) && v >= 0 && v <= 1
}

// adjudicateRefined 对分类器结果重排后应用同一裁决规则；分差仍贴近则返回 false。
func adjudicateRefined(refined []Candidate, snap *Snapshot) (Candidate, bool) {
	if len(refined) == 0 {
		return Candidate{}, false
	}
	sorted := append([]Candidate(nil), refined...)
	sortCandidates(sorted)
	if len(sorted) > 1 && sorted[0].Confidence-sorted[1].Confidence < snap.margin {
		return Candidate{}, false
	}
	return sorted[0], true
}

func sortCandidates(cands []Candidate) {
	sort.SliceStable(cands, func(i, j int) bool {
		a, b := cands[i], cands[j]
		if a.Confidence != b.Confidence {
			return a.Confidence > b.Confidence
		}
		if a.Priority != b.Priority {
			return a.Priority > b.Priority
		}
		return a.ID < b.ID
	})
}

func trimHits(hits []specHit, n int) []specHit {
	if len(hits) > n {
		return hits[:n]
	}
	return hits
}

// Explain 输出单条输入的裁决轨迹（guard 与 rules 全量、确定性、无识别器状态）。
// 这是配置规范要求的只读诊断；intentctl explain 在此之上构建。
func (s *Snapshot) Explain(input string) Trace {
	trace := Trace{InputLen: len(input), AmbiguityMargin: s.margin}
	if strings.TrimSpace(input) == "" {
		trace.Branch = BranchFallback
		return trace
	}
	matchInput, folded := s.foldInput(input)

	for _, idx := range s.guardIdx {
		cs := s.specs[idx]
		o := cs.evaluate(matchInput, folded)
		if o.passed {
			trace.Guard = append(trace.Guard, ScoredSpec{ID: cs.spec.ID, Score: o.score, HitTerms: o.hitTerms, HitPatterns: o.hitPat})
		} else {
			trace.GuardRejected = append(trace.GuardRejected, RejectedSpec{ID: cs.spec.ID, Reason: o.reject})
		}
	}
	sortScored(trace.Guard)
	sortRejected(trace.GuardRejected)
	if len(trace.Guard) > 0 {
		trace.Branch = BranchGuardHit
		trace.TopID = trace.Guard[0].ID
		return trace
	}

	var hits []specHit
	for _, cs := range s.specs {
		if cs.guard {
			continue
		}
		o := cs.evaluate(matchInput, folded)
		if o.passed {
			hits = append(hits, specHit{cs: cs, score: o.score, terms: o.hitTerms, pats: o.hitPat})
			trace.Rules = append(trace.Rules, ScoredSpec{ID: cs.spec.ID, Score: o.score, HitTerms: o.hitTerms, HitPatterns: o.hitPat})
		} else {
			trace.RulesRejected = append(trace.RulesRejected, RejectedSpec{ID: cs.spec.ID, Reason: o.reject})
		}
	}
	sortHits(hits)
	sortScored(trace.Rules)
	sortRejected(trace.RulesRejected)

	switch {
	case len(hits) == 0:
		trace.Branch = BranchFallback
	case len(hits) == 1 || hits[0].score-hits[1].score >= s.margin || tieBreakByPriority(hits):
		trace.Branch = BranchMatched
		trace.TopID = hits[0].cs.spec.ID
	default:
		trace.Branch = BranchAmbiguous
	}
	return trace
}

func sortScored(ss []ScoredSpec) {
	sort.SliceStable(ss, func(i, j int) bool { return ss[i].ID < ss[j].ID })
}

func sortRejected(rs []RejectedSpec) {
	sort.SliceStable(rs, func(i, j int) bool { return rs[i].ID < rs[j].ID })
}

// semanticRerank 用宿主打分器对歧义候选按 examples 重排（I2）。
// 规则：候选必须来自当前候选集（构造上不可能引入未知 ID）；
// 只取相似度 ≥ 阈值的候选——唯一过阈或前两名分差 ≥ margin 才判 matched，
// 否则保持 ambiguous（与规则裁决同款语义）。打分错误一律记日志并保持 ambiguous。
func (r *FunnelRecognizer) semanticRerank(ctx context.Context, input string, cands []Candidate, snap *Snapshot) (Candidate, bool) {
	type scored struct {
		cand  Candidate
		score float64
	}
	var above []scored
	for _, c := range cands {
		spec, ok := snap.SpecByID(c.ID)
		if !ok || len(spec.Examples) == 0 {
			continue
		}
		s, err := r.sem.Score(ctx, input, spec.Examples)
		if err != nil {
			r.log.Module("intent").WithContext(ctx).Warn("intent semantic scorer failed; keep ambiguous",
				"error", err.Error(), "id", c.ID)
			continue
		}
		if s >= r.thr {
			above = append(above, scored{cand: c, score: s})
		}
	}
	if len(above) == 0 {
		return Candidate{}, false
	}
	for i := 0; i+1 < len(above); i++ {
		for j := i + 1; j < len(above); j++ {
			if above[j].score > above[i].score {
				above[i], above[j] = above[j], above[i]
			}
		}
	}
	if len(above) == 1 || above[0].score-above[1].score >= snap.margin {
		return above[0].cand, true
	}
	return Candidate{}, false
}

// generateCommands 经模型命令生成端口兜底（I2）。校验：
// start 的 ActionRef 可解析（spec ID 集或 Handler 集内）、命令种类受限、
// 槽位键在目标 spec 的键集内（可解析时）；全部通过则把首个 start 的目标
// spec 合成 Top（refined_by=generator 标注），任一项不过则保持 fallback。
func (r *FunnelRecognizer) generateCommands(ctx context.Context, input string, snap *Snapshot) (Result, bool) {
	catalog := snap.CatalogTopK(DefaultGeneratorCatalogK)
	cmds, err := r.gen.Generate(ctx, input, catalog)
	if err != nil {
		r.log.Module("intent").WithContext(ctx).Warn("intent command generator failed; keep fallback", "error", err.Error())
		return Result{}, false
	}
	if err := validateGenerated(cmds, catalog); err != nil {
		r.log.Module("intent").WithContext(ctx).Warn("intent generator output rejected; keep fallback", "error", err.Error())
		return Result{}, false
	}
	res := Result{Input: input, Branch: BranchFallback, Commands: cmds, SnapshotRevision: snap.rev}
	for _, c := range cmds {
		if c.Kind != CommandStart {
			continue
		}
		if spec, ok := generatedSpecOf(c.Action, catalog); ok {
			top := Candidate{
				ID: spec.ID, Domain: spec.Domain, Version: spec.Version,
				Confidence: 0, Reason: "generated_by=command_generator",
				Slots: c.Slots,
			}
			res.Top = &top
			res.Branch = BranchMatched
			res.Candidates = []Candidate{top}
		}
		break
	}
	return res, true
}

// DefaultGeneratorCatalogK 生成器目录默认 top-k。
const DefaultGeneratorCatalogK = 8

// validateGenerated 校验生成命令（I2；与 spec 级校验同款 fail-closed）。
func validateGenerated(cmds []Command, catalog []CatalogSpec) error {
	if len(cmds) == 0 {
		return fmt.Errorf("empty command list")
	}
	specIDs := map[string]bool{}
	handlers := map[string]bool{}
	slotKeys := map[string]map[string]bool{}
	for _, cs := range catalog {
		specIDs[cs.ID] = true
		if cs.Handler != "" {
			handlers[cs.Handler] = true
		}
		keys := map[string]bool{}
		for _, sl := range cs.Slots {
			keys[sl.Key] = true
		}
		slotKeys[cs.ID] = keys
	}
	for i, c := range cmds {
		switch c.Kind {
		case CommandStart:
			ref := c.Action
			switch ref.Kind {
			case ActionAuto, ActionCommand, ActionWorkflow, ActionBlueprint:
				if !specIDs[ref.ID] {
					return fmt.Errorf("cmd[%d] start: action.id %q 不在目录内", i, ref.ID)
				}
			case ActionHandler:
				if !handlers[ref.ID] {
					return fmt.Errorf("cmd[%d] start: handler %q 不在目录内", i, ref.ID)
				}
			default:
				return fmt.Errorf("cmd[%d] start: 未知 action.kind %q", i, ref.Kind)
			}
			if keys, ok := slotKeys[ref.ID]; ok {
				for k := range c.Slots {
					if !keys[k] {
						return fmt.Errorf("cmd[%d] start: 槽位 %q 不在 %s 的槽位键集内", i, k, ref.ID)
					}
				}
			}
		case CommandClarify, CommandCancel, CommandSetSlot, CommandChangeSlot, CommandChitchat, CommandHandoff:
		default:
			return fmt.Errorf("cmd[%d]: 未知命令种类 %q", i, c.Kind)
		}
	}
	return nil
}

// generatedSpecOf 把 start 的 ActionRef 解析回目录 spec（handler 键按 Handler 反查）。
func generatedSpecOf(ref ActionRef, catalog []CatalogSpec) (CatalogSpec, bool) {
	for _, cs := range catalog {
		if ref.Kind == ActionHandler {
			if cs.Handler == ref.ID {
				return cs, true
			}
			continue
		}
		if cs.ID == ref.ID {
			return cs, true
		}
	}
	return CatalogSpec{}, false
}