package quota

import (
	"fmt"
	"math"
	"strings"
)

// Multipliers are the z.ai credit formula coefficients (per 10k tokens,
// docs.z.ai/devpack/overview). Family selects by concrete model name; the
// flash tier (GLM-5.3-Flash, routed from glm-4.7*) is the cheap one.
type Multipliers struct {
	Input        float64
	CachedInput  float64
	Output       float64
}

// Flagship multipliers: GLM-5.3 (and everything auto-routed to it).
func FlagshipMultipliers() Multipliers { return Multipliers{Input: 6.9, CachedInput: 1.7, Output: 24} }

// Flash multipliers: GLM-5.3-Flash (and glm-4.7* routing).
func FlashMultipliers() Multipliers { return Multipliers{Input: 2.3, CachedInput: 0.56, Output: 8} }

// MultipliersFor maps a concrete proxy model name to its credit multiplier
// family. Unknown models read as flagship (conservative: overestimate cost
// rather than silently burn quota).
func MultipliersFor(model string) Multipliers {
	m := strings.ToLower(model)
	switch {
	case strings.Contains(m, "flash"):
		return FlashMultipliers()
	default:
		return FlagshipMultipliers()
	}
}

// EstimateCredits computes the z.ai credits one turn consumed from its token
// usage: (input*in + cached*cache + output*out) / 10000, halved when the
// turn ran off-peak (z.ai charges 50% outside peak hours).
func EstimateCredits(model string, promptTokens, cachedTokens, completionTokens int, peak bool) float64 {
	mult := MultipliersFor(model)
	credits := (float64(promptTokens)*mult.Input +
		float64(cachedTokens)*mult.CachedInput +
		float64(completionTokens)*mult.Output) / 10000
	if !peak {
		credits /= 2
	}
	// Round to 6 decimals: keeps redis INCRBYFLOAT values readable and the
	// JSONL compact; sub-microcredit noise is meaningless.
	return math.Round(credits*1e6) / 1e6
}

// EstimateTurnInput is the per-turn usage record the loop hands the gate.
type EstimateTurnInput struct {
	Model            string
	PromptTokens     int
	CachedTokens     int
	CompletionTokens int
	Peak             bool // turn ran inside the peak window
}

// Describe renders a human summary of one turn's credit cost (logs, REPORTs).
func (e EstimateTurnInput) Describe() string {
	return fmt.Sprintf("%s: %d/%d/%d tokens (in/cached/out) %s = %.4f credits",
		e.Model, e.PromptTokens, e.CachedTokens, e.CompletionTokens,
		peakTag(e.Peak), EstimateCredits(e.Model, e.PromptTokens, e.CachedTokens, e.CompletionTokens, e.Peak))
}

func peakTag(peak bool) string {
	if peak {
		return "peak"
	}
	return "off-peak"
}