package mcp

import (
	"time"

	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
)

// pendingNudgeThreshold is how old a raw/ note has to be before brain_context
// mentions the queue. Two weeks: long enough that a note written this sprint
// does not nag, short enough that four items cannot sit unnoticed for three
// months again (#82).
const pendingNudgeThreshold = 14 * 24 * time.Hour

// PendingNudge is the in-session reminder that the promote/reject queue has
// items waiting. It is advisory: a count, an age, and how to look.
type PendingNudge struct {
	Pending    int    `json:"pending"`     // everything in the queue
	Aging      int    `json:"aging"`       // those past the threshold
	Oldest     string `json:"oldest"`      // filename of the oldest pending note
	OldestDays int    `json:"oldest_days"` // its age, in whole days
	Hint       string `json:"hint"`
}

// pendingNudge summarises the raw/ review queue, or returns nil when there is
// nothing worth saying.
//
// The trigger is the missing half of the queue (#82): brain_pending has always
// existed, and four real items still sat unreviewed from 2026-04-23 to
// 2026-07-15 because nothing ever prompted anyone to call it. The system
// should be what remembers the queue exists.
//
// Threshold-gated on purpose. A notice on every context call is one people
// learn to skip, which reproduces the original failure with extra steps.
//
// It never promotes, rejects, or reorders anything. Age is a reason to ask a
// human, not a verdict — an old note may be exactly right to promote once
// someone finally looks at it.
func pendingNudge(brainDir string, now time.Time, threshold time.Duration) *PendingNudge {
	pending, err := api.ListPending(brainDir)
	if err != nil || len(pending) == 0 {
		// brain_context is a hot path; a broken queue degrades to silence
		// rather than failing the call that asked for project context.
		return nil
	}

	var aging int
	var oldestName string
	var oldestAge time.Duration

	for _, p := range pending {
		created, perr := time.Parse(time.RFC3339, p.CreatedAt)
		if perr != nil {
			continue // an unparseable timestamp is not evidence of age
		}
		age := now.Sub(created)
		if age >= threshold {
			aging++
		}
		if age > oldestAge {
			oldestAge, oldestName = age, p.Filename
		}
	}

	if aging == 0 {
		return nil
	}

	return &PendingNudge{
		Pending:    len(pending),
		Aging:      aging,
		Oldest:     oldestName,
		OldestDays: int(oldestAge.Hours() / 24),
		Hint:       "call brain_pending to review; nothing is promoted or rejected automatically",
	}
}