package runner

import (
	"fmt"
	"sync"
	"time"

	"cast-loadtest/internal/config"
	"cast-loadtest/internal/sender"
	"cast-loadtest/internal/stats"
)

func Run(cfg config.Config) {
	fmt.Println("========================================")
	fmt.Println("       SMS API LOAD TESTER (Go)         ")
	fmt.Println("========================================")
	fmt.Println()
	fmt.Println("--- API Configuration ---")
	fmt.Printf("  Target:     %s\n", cfg.APIURL)
	fmt.Printf("  API Key:    %s...%s\n", cfg.APIKey[:9], cfg.APIKey[len(cfg.APIKey)-4:])
	fmt.Printf("  Sender ID:  %s\n", cfg.SenderID)
	fmt.Printf("  Recipient:  %s\n", cfg.Recipient)
	fmt.Println()
	fmt.Println("--- Message Configuration ---")
	fmt.Printf("  SMS Parts:  %d\n", cfg.MsgParts)
	fmt.Printf("  Max Chars:  %d\n", cfg.MsgParts*140)
	fmt.Println()
	fmt.Println("--- Test Parameters ---")
	fmt.Printf("  Threads:    %d\n", cfg.Threads)
	fmt.Printf("  Target RPS: %d\n", cfg.RPS)
	fmt.Printf("  Duration:   %ds\n", cfg.DurationSec)
	fmt.Printf("  Ramp-up:    %ds\n", cfg.RampUpSec)
	fmt.Println()

	// Warnings
	hasWarning := false
	if cfg.RampUpSec >= cfg.DurationSec {
		fmt.Println("WARNING: Ramp-up >= duration. The test will never reach full RPS.")
		fmt.Printf("         Reduce LOAD_TEST_RAMP_UP_SECS (currently %ds) below duration (%ds).\n", cfg.RampUpSec, cfg.DurationSec)
		hasWarning = true
	}
	// Estimate: need threads >= RPS * avg_latency_secs. Assume ~500ms avg latency.
	estimatedLatency := 0.5
	minThreads := int(float64(cfg.RPS)*estimatedLatency) + 1
	if cfg.Threads < minThreads {
		fmt.Printf("WARNING: Threads (%d) may be too low for target RPS (%d).\n", cfg.Threads, cfg.RPS)
		fmt.Printf("         Recommended: at least %d threads (based on ~%.0fms estimated latency).\n", minThreads, estimatedLatency*1000)
		hasWarning = true
	}
	if hasWarning {
		fmt.Println()
	}

	fmt.Println("========================================")
	fmt.Println()

	client := sender.NewHTTPClient(cfg.Threads)
	st := &stats.Stats{}
	duration := time.Duration(cfg.DurationSec) * time.Second
	rampUp := time.Duration(cfg.RampUpSec) * time.Second

	// Ticker for live stats
	statsTicker := time.NewTicker(500 * time.Millisecond)
	defer statsTicker.Stop()

	testStart := time.Now()
	done := make(chan struct{})

	// Live stats printer
	go func() {
		for {
			select {
			case <-statsTicker.C:
				st.PrintLive(time.Since(testStart))
			case <-done:
				return
			}
		}
	}()

	// Rate limiter with ramp-up
	var wg sync.WaitGroup
	sem := make(chan struct{}, cfg.Threads)

	targetRPS := cfg.RPS
	ticker := time.NewTicker(time.Second / time.Duration(targetRPS))
	defer ticker.Stop()

	fmt.Println("Starting load test...")
	fmt.Println()

	for {
		elapsed := time.Since(testStart)
		if elapsed >= duration {
			break
		}

		// Ramp-up: scale RPS linearly
		currentRPS := targetRPS
		if elapsed < rampUp && rampUp > 0 {
			rampFraction := float64(elapsed) / float64(rampUp)
			currentRPS = int(float64(targetRPS) * rampFraction)
			if currentRPS < 1 {
				currentRPS = 1
			}
			ticker.Reset(time.Second / time.Duration(currentRPS))
		} else if elapsed >= rampUp {
			ticker.Reset(time.Second / time.Duration(targetRPS))
		}

		<-ticker.C

		sem <- struct{}{}
		wg.Add(1)
		go func() {
			defer wg.Done()
			defer func() { <-sem }()
			sender.SendSMS(client, cfg, st)
		}()
	}

	// Wait for in-flight requests
	fmt.Println("\n\nWaiting for in-flight requests to complete...")
	wg.Wait()
	close(done)

	st.PrintFinalReport(time.Since(testStart))
}