package adminapi

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

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

// PriceStore is what a price is suggested from: what each model held of
// the cluster, and the tokens it served.
type PriceStore interface {
	HeldSince(ctx context.Context, since time.Time) ([]store.Held, time.Time, error)
	UsageByModel(ctx context.Context, since time.Time) ([]store.ModelUsage, error)
}

// PriceConfig is the cost basis and the prices in force.
type PriceConfig struct {
	Basis   accounting.Basis
	Current map[string]accounting.Price
	Default accounting.Price
}

// PriceSuggestions is a model's price from its cost, for each model.
type PriceSuggestions struct {
	// Days is the window; RecordedFrom the first hour held is known for,
	// later than the window's start on a cluster that began keeping it
	// since, which makes the window shorter than asked.
	Days         int               `json:"days"`
	Since        time.Time         `json:"since"`
	RecordedFrom time.Time         `json:"recorded_from,omitempty"`
	GPUHourCost  float64           `json:"gpu_hour_cost"`
	CoreHourCost float64           `json:"core_hour_cost"`
	Models       []PriceSuggestion `json:"models"`
}

// PriceSuggestion is one model's.
type PriceSuggestion struct {
	accounting.Suggestion
	Current accounting.Price `json:"current"`
}

// SetPrices gives the API what prices are suggested from.
func (a *API) SetPrices(st PriceStore, cfg func() PriceConfig) { a.prices, a.priceCfg = st, cfg }

func (a *API) registerPrices(mux Mux) {
	mux.HandleFunc("GET /api/v1/prices/suggest", a.suggestPrices)
}

func (a *API) suggestPrices(w http.ResponseWriter, r *http.Request) {
	if a.prices == nil || a.priceCfg == nil {
		writeError(w, http.StatusNotImplemented, "prices are suggested from the store, which this control plane runs without")
		return
	}
	days := 30
	if v := r.URL.Query().Get("days"); v != "" {
		n, err := strconv.Atoi(v)
		if err != nil || n < 1 || n > 366 {
			writeError(w, http.StatusBadRequest, "days is a whole number of days, 1 to 366")
			return
		}
		days = n
	}
	cfg := a.priceCfg()
	if cfg.Basis.GPUHour <= 0 && cfg.Basis.CoreHour <= 0 {
		writeError(w, http.StatusConflict, "no cost to price from: set auth.gpu_hour_cost (and auth.core_hour_cost for "+
			"models on CPUs), what an hour of one costs, in the units budgets are in")
		return
	}
	since := time.Now().Add(-time.Duration(days) * 24 * time.Hour)
	rows, first, err := a.prices.HeldSince(r.Context(), since)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	// Tokens from when holding was first recorded, so both sides cover the
	// same hours.
	from := since
	if first.After(from) {
		from = first
	}
	usage, err := a.prices.UsageByModel(r.Context(), from)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	held := map[string]accounting.Held{}
	for _, h := range rows {
		held[h.Model] = accounting.Held{GPUSeconds: h.GPUSeconds, CoreSeconds: h.CoreSeconds}
	}
	served := map[string]accounting.Served{}
	for _, u := range usage {
		served[u.Model] = accounting.Served{Prompt: u.Prompt, Completion: u.Completion}
	}
	out := PriceSuggestions{Days: days, Since: since.UTC(), RecordedFrom: first,
		GPUHourCost: cfg.Basis.GPUHour, CoreHourCost: cfg.Basis.CoreHour, Models: []PriceSuggestion{}}
	for _, s := range accounting.Suggest(held, served, cfg.Basis) {
		cur, ok := cfg.Current[s.Model]
		if !ok {
			cur = cfg.Default
		}
		out.Models = append(out.Models, PriceSuggestion{Suggestion: s, Current: cur})
	}
	writeJSON(w, http.StatusOK, out)
}