// Package wing decides which brain wing an incoming raw note belongs to
// without the human typing it (hyperguild#205, #208).
//
// An earlier design classified each note with a local model and cross-checked
// it with a text score. Measured against pages whose wing a human had chosen,
// the model was right 60% of the time with a saturated self-reported
// confidence, and the cross-check was right 11% of the time, so the gate it
// formed placed 2 of 55 pages (hyperguild#208). The Router that replaced it
// decides with rules only: a deliberate folder or frontmatter wing, else one
// default wing; nothing it cannot decide safely is guessed.
package wing

import (
	"context"
	"strings"
)

// Source says how a Decision was reached.
type Source string

const (
	Explicit  Source = "explicit"  // subfolder or frontmatter named the wing
	Default   Source = "default"   // no signal; the configured default wing
	Exception Source = "exception" // needs a human
)

// Note is what the Placer sees of an incoming raw note.
type Note struct {
	Dir             string // first subfolder under raw/, "" when dropped at the top
	FrontmatterWing string // `wing:` from the note's frontmatter, "" if absent
	Text            string
}

// Decision is the outcome. For an Exception, Wing holds the proposal when
// there was one (so a reviewer can approve it) and is empty otherwise.
type Decision struct {
	Wing       string
	Source     Source
	Confidence float64
	Reason     string
}

// Placer decides where a raw note goes. Router is the production
// implementation; the interface lets the watcher stay ignorant of how.
type Placer interface {
	Resolve(ctx context.Context, n Note) Decision
}

func exception(w string, conf float64, reason string) Decision {
	return Decision{Wing: w, Source: Exception, Confidence: conf, Reason: reason}
}

func norm(s string) string { return strings.ToLower(strings.TrimSpace(s)) }