package web

import (
	"context"
	"net/http"
	"time"

	"gitea.mynodes.xyz/ilker/llmgw/internal/promq"
	"gitea.mynodes.xyz/ilker/llmgw/internal/store"
)

// UsageAdmin is the store half of the usage report.
type UsageAdmin interface {
	UsageBucketsBy(ctx context.Context, g store.Grouping,
		since time.Time, width time.Duration) ([]store.UsageSeries, error)
}

// usageWindow is one length of history the page offers, and the slice it is cut
// into.
//
// The bucket width is chosen with the window rather than separately. A day in
// five-minute slices is 288 points across 720 pixels, which is a texture; a
// month in five-minute slices is 8,640, which is a smear. Roughly fifty to a
// hundred points is what a line of this size can actually show.
type usageWindow struct {
	Key   string
	Label string
	Span  time.Duration
	Width time.Duration
}

var usageWindows = []usageWindow{
	{"24h", "last 24 hours", 24 * time.Hour, 20 * time.Minute},
	{"7d", "last 7 days", 7 * 24 * time.Hour, 2 * time.Hour},
	{"30d", "last 30 days", 30 * 24 * time.Hour, 12 * time.Hour},
}

func windowFor(key string) usageWindow {
	for _, w := range usageWindows {
		if w.Key == key {
			return w
		}
	}
	return usageWindows[1]
}

// usageGroup names one grouping for the chooser.
type usageGroup struct {
	Key      string
	Label    string
	Selected bool
}

// usageRow is one group's totals, shown under the charts.
type usageRow struct {
	Name     string
	Requests int64
	Tokens   int64
	Spend    string
	Errors   int64
}

type adminUsageData struct {
	Groups  []usageGroup
	Windows []struct {
		Key, Label string
		Selected   bool
	}
	By     string
	Window string

	Requests TimeSeries
	Tokens   TimeSeries
	Spend    TimeSeries

	Rows []usageRow
	// Priced is false when no model has a price, which makes the spend chart a
	// flat zero however busy the cluster is. Said rather than drawn, because a
	// chart along the bottom reads as "nobody spent anything".
	Priced bool

	Error   string
	Version string
	Now     string
}

// RegisterAdminUsage mounts the usage report under /admin/usage.
//
// Separate from the quotas page although both read the same tree. Quotas is a
// page for writing a number and seeing whether it is being approached; this one
// answers "who is using the cluster, and when" — including per person, which is
// not a level quotas can be written on at all.
func (p *AccountPages) RegisterAdminUsage(mux *http.ServeMux, s UsageAdmin, priced Priced) {
	mux.HandleFunc("GET /admin/usage", p.AdminPage(
		func(w http.ResponseWriter, r *http.Request) {
			p.renderUsage(w, r, s, priced)
		}))
}

func (p *AccountPages) renderUsage(w http.ResponseWriter, r *http.Request,
	s UsageAdmin, priced Priced,
) {
	by := store.Grouping(r.URL.Query().Get("by"))
	if !by.Valid() {
		by = store.GroupByTeam
	}
	win := windowFor(r.URL.Query().Get("window"))

	d := adminUsageData{
		By: string(by), Window: win.Key,
		Priced:  priced != nil && priced.AnythingPriced(),
		Version: p.version,
		Now:     time.Now().UTC().Format(time.RFC3339),
	}
	for _, g := range store.Groupings() {
		d.Groups = append(d.Groups, usageGroup{
			Key: string(g), Label: groupLabel(g), Selected: g == by,
		})
	}
	for _, uw := range usageWindows {
		d.Windows = append(d.Windows, struct {
			Key, Label string
			Selected   bool
		}{uw.Key, uw.Label, uw.Key == win.Key})
	}

	rows, err := s.UsageBucketsBy(r.Context(), by, time.Now().Add(-win.Span), win.Width)
	if err != nil {
		p.log.Error("could not read usage over time", "by", by, "err", err)
		d.Error = "could not read usage"
		render(w, "admin_usage", d)
		return
	}

	d.Requests = LineChartTotals(seriesOf(rows, func(b store.Bucket) float64 {
		return float64(b.Requests)
	}), "", 4)
	d.Tokens = LineChartTotals(seriesOf(rows, func(b store.Bucket) float64 {
		return float64(b.Prompt + b.Completion)
	}), "", 4)
	d.Spend = LineChartTotals(seriesOf(rows, func(b store.Bucket) float64 {
		// Shown in whole units, as every other spend figure is: a budget is
		// written in units and a chart in micros would not compare with it.
		return float64(b.CostMicros) / 1e6
	}), "", 4)

	for _, u := range rows {
		d.Rows = append(d.Rows, usageRow{
			Name:     displayName(u),
			Requests: u.Requests,
			Tokens:   u.Tokens(),
			Spend:    unitsOf(u.CostMicros),
			Errors:   u.Errors,
		})
	}
	render(w, "admin_usage", d)
}

// seriesOf turns each group's buckets into a line of one measure.
//
// One pass per measure rather than one query per measure: the buckets are
// already in memory and already share a clock, and three queries that could
// disagree about the window is a worse answer than three loops.
func seriesOf(rows []store.UsageSeries, value func(store.Bucket) float64) []promq.Series {
	out := make([]promq.Series, 0, len(rows))
	for _, u := range rows {
		s := promq.Series{Name: displayName(u)}
		for _, b := range u.Buckets {
			s.Points = append(s.Points, promq.Point{At: b.Start, Value: value(b)})
		}
		out = append(out, s)
	}
	return out
}

// displayName is what a line and a row are labelled with.
//
// A person with no account is named rather than left blank: keys issued before
// accounts existed carry real traffic, and an unlabelled line in a legend is
// the one nobody can act on.
func displayName(u store.UsageSeries) string {
	if u.Name != "" {
		return u.Name
	}
	if u.Grouping == store.GroupByUser {
		return "keys with no owner"
	}
	if u.ID != "" {
		return u.ID
	}
	return "unknown"
}

func groupLabel(g store.Grouping) string {
	switch g {
	case store.GroupByOrg:
		return "organization"
	case store.GroupByTeam:
		return "team"
	case store.GroupByProject:
		return "project"
	case store.GroupByUser:
		return "person"
	default:
		return string(g)
	}
}