// Package capacity implements the "awakened capacity" decision layer
// (DevDocs/design/14-唤醒式能力渐进.md). It sits outside the loop core: every
// round, it classifies the conversation into one of three states — quiet /
// awake / full — and yields the set of tools that this round may expose to the
// model. The loop then advertises only that allowed set to the model (a view
// over the dispatcher, never a hard boundary: Invoke is left unblocked so an
// emergency call still works — capacity is a decision, not a capability wall).
//
// Intent is judged in layers and defaults to conservative (低置信→静息): L1
// fast heuristics (strong action signals → awake/full, clear companion signals →
// quiet), falling to L2 context trend (recent turns), then L4 learned-habit
// alignment (recalled user habits correct/fill the intent — design §2.2, §2.4),
// before the persona awakening override (design §3). It never uses intent for
// identity — identity stays on channel actor metadata (project red line).
package capacity

import (
	"context"
	"log/slog"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
)

// State is one of the three awakened-capacity states (design §1).
type State string

const (
	// StateQuiet is the default: 静·陪伴. Only a narrow, companion-safe tool face
	// is exposed (terminal + file edit + memory/emotion companion).
	StateQuiet State = "quiet"
	// StateAwake is 醒·办事: a real task is detected and tools wake one by one
	// (web retrieval, file, terminal).
	StateAwake State = "awake"
	// StateFull is 全·复杂任务: the complete capability window.
	StateFull State = "full"
)

// EventType labels a state-change event.
const EventAwaken = "capacity_awaken"

// Event describes a visible capacity transition (design §1/§4): a state changed
// and a tool was lit up, surfaced to the frontend. A change to quiet does not
// emit (only awakenings are surfaced).
type Event struct {
	Type      string
	FromState State
	ToState   State
	// Tool is the tool that this transition lit up (点亮工具). Empty when no
	// single tool can be named.
	Tool string
	// At is the wall-clock time the transition was observed.
	At time.Time
	// SessionID is set by the runtime layer (loop) to the conversation session the
	// transition belongs to, so the frontend targets the correct session rather
	// than treating the event as global. It is empty when the emitter never ran
	// inside a session-scoped turn (e.g. a direct toolSchemas call in a unit test).
	SessionID string
}

// IsAwaken reports whether the event is a capacity_awaken transition.
func (e Event) IsAwaken() bool { return e.Type == EventAwaken }

// Decision is the outcome of one Decide call (design §4). Judgment is the raw
// intent-layer classification (before any persona override), suitable for write-back
// into memory so the L4 layer learns the user's task-expression habits (design §2.4).
type Decision struct {
	State        State
	AllowedTools []string
	Events       []Event
	Confidence   float64
	Judgment     Judgment
}

// Awakening is the persona-level override block (design §3,
// configs/personas/*.yaml → awakening). It is per-persona; the zero value means
// "no override" so the policy falls back to conservative defaults.
type Awakening struct {
	// DefaultState is the persona's resting tendency (default_state) used when
	// the intent layers are ambiguous. Empty = quiet.
	DefaultState State
	// MinConfidence overrides the global wake threshold; a positive value wins
	// over Config.MinConfidence. Below it, the intent is forced toward the
	// persona default (conservative, 不打扰).
	MinConfidence float64
	// ForceState, when set, unconditionally pins a state (force_state), e.g. a
	// "干练助理" persona defaults to awake regardless of intent.
	ForceState State
}

// IsZero reports whether no override is configured.
func (a Awakening) IsZero() bool {
	return a.DefaultState == "" && a.MinConfidence == 0 && a.ForceState == ""
}

// Config configures a Decider. A zero value disables capacity (all tools always
// surface), so the loop's pre-existing behavior is preserved until enabled.
type Config struct {
	// Enabled gates the whole decision layer. When false Decide returns every
	// tool and emits no events.
	Enabled bool
	// MinConfidence is the wake threshold below which the state is forced toward
	// the persona default (设计 §2.3 默认保守). Zero selects the default 0.6.
	MinConfidence float64
	// ToolSets maps a State to the allowed tool names. A missing entry selects
	// the built-in default set for that state; a nil entry means "no
	// restriction" (all tools); an empty non-nil slice means "no tools". StateFull
	// maps to nil (complete window) unless overridden.
	ToolSets map[State][]string
	// Awakening carries the persona-level override (design §3). Zero = no
	// override.
	Awakening Awakening
}

// Input is everything Decide needs to classify one round (design §4).
type Input struct {
	// Messages is the conversation text in chronological order (oldest first);
	// the last element is the current turn. Text is extracted by the caller so
	// the capacity package stays decoupled from the model message type.
	Messages []string
	// CurrentState is the state the agent occupied at the start of this round,
	// used purely to emit the FromState of a transition. An empty value is
	// treated as StateQuiet.
	CurrentState State
	// Awakening, when non-zero, overrides the Config.Awakening for this call
	// (per-persona override).
	Awakening Awakening
	// AllToolNames is the full set of known tool-spec names the dispatcher can
	// advertise; the allowed set is derived by intersecting the state's set
	// with it (preserving AllToolNames order).
	AllToolNames []string
	// Recall carries the owner's recalled habit memories for this round (design
	// §2.2 L4), filled by the caller from Retriever.Retrieve. L4 uses it to correct
	// or fill in the intent with learned user habits. Nil or empty keeps L4 silent,
	// so L1/L2 behavior is unchanged (向后兼容).
	Recall []RecallItem
}

// Option configures a Decider at construction time.
type Option func(*Decider)

// Decider is the awakened-capacity decision engine. It is immutable after New
// and safe for concurrent Decide calls.
type Decider struct {
	cfg Config
	log *slog.Logger
}

// sourcedLog returns a logger tagged with the module source (project rule §10),
// replacing a nil logger with a discard one so decide can always log safely.
func sourcedLog(l *slog.Logger) *slog.Logger {
	if l == nil {
		l = slog.New(slog.NewTextHandler(discard{}, nil))
	}
	return logger.WithSource(l, "runtime/capacity")
}

// discard is an io.Writer that drops everything; it sits behind a nil logger so
// no log dependency is forced on a caller that never logs.
type discard struct{}

func (discard) Write(p []byte) (int, error) { return len(p), nil }

// WithLogger injects the base logger. Nil is replaced with a discard logger
// tagged with source "runtime/capacity".
func WithLogger(l *slog.Logger) Option {
	return func(d *Decider) { d.log = sourcedLog(l) }
}

// New builds a Decider from cfg, applying opts in order. It applies the
// default MinConfidence of 0.6 when the config leaves it at zero.
func New(cfg Config, opts ...Option) *Decider {
	if cfg.MinConfidence <= 0 {
		cfg.MinConfidence = DefaultMinConfidence
	}
	d := &Decider{cfg: cfg}
	d.log = sourcedLog(nil)
	for _, opt := range opts {
		if opt != nil {
			opt(d)
		}
	}
	return d
}

// DefaultMinConfidence is the conservative wake threshold (design §2.3).
const DefaultMinConfidence = 0.6

// Enabled reports whether the decision layer is active.
func (d *Decider) Enabled() bool { return d.cfg.Enabled }

// Decide classifies one round and returns the state, allowed tool set and any
// transition events. When capacity is disabled it returns the full tool set and
// no events, preserving the loop's default behavior.
func (d *Decider) Decide(ctx context.Context, in Input) Decision {
	if !d.cfg.Enabled {
		return Decision{State: in.CurrentState, AllowedTools: append([]string(nil), in.AllToolNames...)}
	}
	state, conf, tool := d.intent(in)
	j := judgmentFor(in, state, conf, tool)
	state, conf = d.applyAwakening(state, conf, in)
	allowed := d.allowedTools(state, in.AllToolNames)
	events := d.stateEvents(effectiveState(in.CurrentState), state, tool, allowed)

	d.log.Debug("capacity decide",
		"from", effectiveState(in.CurrentState), "to", state,
		"confidence", conf, "allowed", len(allowed), "tool", tool,
		"is_task", j.IsTask, "task_kind", j.TaskKind)
	return Decision{State: state, AllowedTools: allowed, Events: events, Confidence: conf, Judgment: j}
}

// effectiveAwakening returns the per-call Awakening when set, else the config's.
func (d *Decider) effectiveAwakening(in Input) Awakening {
	if !in.Awakening.IsZero() {
		return in.Awakening
	}
	return d.cfg.Awakening
}

// applyAwakening overlays the persona override (design §3, B) on the intent
// layer result (A): force_state pins unconditionally; otherwise a result below
// the effective threshold falls back to the persona default (conservative).
func (d *Decider) applyAwakening(state State, conf float64, in Input) (State, float64) {
	aw := d.effectiveAwakening(in)
	if aw.ForceState != "" {
		return aw.ForceState, conf
	}
	minConf := d.cfg.MinConfidence
	if aw.MinConfidence > 0 {
		minConf = aw.MinConfidence
	}
	if conf < minConf || state == "" {
		if def := aw.DefaultState; def != "" {
			return def, conf
		}
		return StateQuiet, conf
	}
	return state, conf
}

// allowedTools returns the state's allowed set intersected with the known tool
// names, preserving AllToolNames order. StateFull (and any state whose set is
// nil) is unrestricted and returns the full tool list.
func (d *Decider) allowedTools(state State, all []string) []string {
	set := d.toolSetFor(effectiveState(state))
	if set == nil {
		return all
	}
	return intersectOrdered(set, all)
}

// toolSetFor returns the configured or built-in allowed set for state. A nil
// return means unrestricted (all tools).
func (d *Decider) toolSetFor(state State) []string {
	if ts, ok := d.cfg.ToolSets[state]; ok {
		if ts == nil {
			return nil
		}
		return ts
	}
	switch state {
	case StateQuiet:
		return defaultQuietTools()
	case StateAwake:
		return defaultAwakeTools()
	default:
		return nil // StateFull → complete window
	}
}

// stateEvents builds the transition event when the state actually changed to a
// more-awake state. tool is the lit tool, taken from the intent or, when empty,
// the first allowed tool in the target state's canonical set (deterministic). A
// change to quiet emits nothing.
func (d *Decider) stateEvents(from, to State, tool string, toAllowed []string) []Event {
	if from == to || to == StateQuiet {
		return nil
	}
	if tool == "" {
		tool = firstAllowedCanonical(d.toolSetFor(to), toAllowed)
	}
	return []Event{{Type: EventAwaken, FromState: from, ToState: to, Tool: tool, At: time.Now()}}
}

// firstAllowedCanonical returns the first tool in the canonical state set that is
// actually allowed (present in allowed). An unrestricted set (nil canonical)
// falls back to the first tool of allowed. It is deterministic because the
// canonical sets use a fixed order, unlike the registry's map iteration order.
func firstAllowedCanonical(canonical, allowed []string) string {
	if len(canonical) == 0 {
		if len(allowed) > 0 {
			return allowed[0]
		}
		return ""
	}
	allowedSet := make(map[string]bool, len(allowed))
	for _, n := range allowed {
		allowedSet[n] = true
	}
	for _, n := range canonical {
		if allowedSet[n] {
			return n
		}
	}
	return ""
}

// intersectOrdered keeps the tools of all that are in allow, preserving the
// all order so the advertised schema list stays stable.
func intersectOrdered(allow, all []string) []string {
	if len(allow) == 0 || len(all) == 0 {
		return []string{}
	}
	allowSet := make(map[string]bool, len(allow))
	for _, a := range allow {
		allowSet[a] = true
	}
	out := make([]string, 0, len(all))
	for _, name := range all {
		if allowSet[name] {
			out = append(out, name)
		}
	}
	return out
}

// effectiveState returns StateQuiet for an empty state, so the CurrentState of
// a nil input is always a valid resting state.
func effectiveState(s State) State {
	if s == "" {
		return StateQuiet
	}
	return s
}