package metrics

import (
	"sort"
	"time"

	"edp.buildth.ing/DevFW-CICD/forgejo-runner-optimiser/internal/cgroup"
	"edp.buildth.ing/DevFW-CICD/forgejo-runner-optimiser/internal/proc"
)

// Aggregator collects and aggregates metrics from processes
type Aggregator struct {
	procPath          string
	topN              int
	prevCPU           *CPUSnapshot
	prevProcCPU       map[int]*ProcessCPUSnapshot
	cgroupLimits      cgroup.CgroupLimits      // container name -> limits
	processMapping    cgroup.ProcessMapping    // process name -> container name
	cgroupPathMapping cgroup.CgroupPathMapping // cgroup path -> container name (built at runtime)
	prevCgroupCPU     map[string]uint64        // container name -> previous total ticks
	prevCgroupTime    time.Time                // previous collection time for cgroup CPU calc
}

// NewAggregator creates a new metrics aggregator
func NewAggregator(procPath string, topN int) *Aggregator {
	// Parse cgroup configuration from environment
	limits, _ := cgroup.ParseCgroupLimitsEnv()
	processMap, _ := cgroup.ParseProcessMappingEnv()

	return &Aggregator{
		procPath:          procPath,
		topN:              topN,
		prevProcCPU:       make(map[int]*ProcessCPUSnapshot),
		cgroupLimits:      limits,
		processMapping:    processMap,
		cgroupPathMapping: make(cgroup.CgroupPathMapping),
		prevCgroupCPU:     make(map[string]uint64),
	}
}

// Collect gathers all system metrics
func (a *Aggregator) Collect() (*SystemMetrics, error) {
	now := time.Now()

	// Read system info
	sysInfo, err := proc.ReadSystemInfo(a.procPath)
	if err != nil {
		return nil, err
	}

	// Read system CPU
	user, nice, system, idle, iowait, irq, softirq, err := proc.ReadSystemCPU(a.procPath)
	if err != nil {
		return nil, err
	}

	currentCPU := &CPUSnapshot{
		Timestamp: now,
		User:      user,
		Nice:      nice,
		System:    system,
		Idle:      idle,
		IOWait:    iowait,
		IRQ:       irq,
		SoftIRQ:   softirq,
	}

	// Calculate CPU percentages
	cpuMetrics := a.calculateCPUMetrics(currentCPU)
	a.prevCPU = currentCPU

	// Read all processes
	processes, err := proc.ReadAllProcesses(a.procPath)
	if err != nil {
		return nil, err
	}

	// Calculate per-process metrics
	processMetrics := a.calculateProcessMetrics(processes, now)

	// Calculate memory metrics
	memMetrics := a.calculateMemoryMetrics(sysInfo, processMetrics)

	// Get top CPU consumers
	topCPU := a.getTopByMetric(processMetrics, func(p ProcessMetrics) float64 {
		return p.CPUPercent
	})

	// Get top memory consumers
	topMemory := a.getTopByMetric(processMetrics, func(p ProcessMetrics) float64 {
		return float64(p.MemRSS)
	})

	// Discover cgroup path mappings from known processes
	a.discoverCgroupMappings(processes)

	// Calculate per-cgroup metrics
	cgroupMetrics := a.calculateCgroupMetrics(processes, processMetrics, now)

	return &SystemMetrics{
		Timestamp:      now,
		TotalProcesses: len(processes),
		CPU:            cpuMetrics,
		Memory:         memMetrics,
		TopCPU:         topCPU,
		TopMemory:      topMemory,
		Cgroups:        cgroupMetrics,
	}, nil
}

// calculateCPUMetrics calculates CPU percentages between snapshots
func (a *Aggregator) calculateCPUMetrics(current *CPUSnapshot) CPUMetrics {
	if a.prevCPU == nil {
		return CPUMetrics{}
	}

	totalDelta := float64(current.Total() - a.prevCPU.Total())
	if totalDelta <= 0 {
		return CPUMetrics{}
	}

	userDelta := float64(current.User+current.Nice) - float64(a.prevCPU.User+a.prevCPU.Nice)
	systemDelta := float64(current.System+current.IRQ+current.SoftIRQ) - float64(a.prevCPU.System+a.prevCPU.IRQ+a.prevCPU.SoftIRQ)
	idleDelta := float64(current.Idle) - float64(a.prevCPU.Idle)
	iowaitDelta := float64(current.IOWait) - float64(a.prevCPU.IOWait)

	return CPUMetrics{
		TotalPercent:  (totalDelta - idleDelta - iowaitDelta) / totalDelta * 100,
		UserPercent:   userDelta / totalDelta * 100,
		SystemPercent: systemDelta / totalDelta * 100,
		IdlePercent:   idleDelta / totalDelta * 100,
		IOWaitPercent: iowaitDelta / totalDelta * 100,
	}
}

// calculateProcessMetrics calculates metrics for each process
func (a *Aggregator) calculateProcessMetrics(processes []*proc.ProcessInfo, now time.Time) []ProcessMetrics {
	newProcCPU := make(map[int]*ProcessCPUSnapshot)
	metrics := make([]ProcessMetrics, 0, len(processes))

	for _, p := range processes {
		pid := p.Stat.PID

		// Calculate CPU percentage for this process
		cpuPercent := 0.0
		if prev, ok := a.prevProcCPU[pid]; ok && a.prevCPU != nil {
			totalDelta := float64(a.prevCPU.Total())
			if a.prevCPU != nil {
				// Use system CPU total delta for process CPU calculation
				currentTotal := a.prevCPU.Total()
				if currentTotal > 0 {
					procDelta := float64(p.Stat.TotalTime()) - float64(prev.Total())
					if procDelta > 0 {
						// Calculate based on elapsed time and clock ticks
						elapsed := now.Sub(prev.Timestamp).Seconds()
						if elapsed > 0 {
							// CPU percent = (process ticks / clock_ticks_per_sec) / elapsed_time * 100
							cpuPercent = (procDelta / float64(proc.DefaultClockTicks)) / elapsed * 100
							if cpuPercent > 100 {
								cpuPercent = 100 // Cap at 100% per CPU
							}
						}
					}
				}
			}
			_ = totalDelta // Avoid unused variable warning
		}

		// Store current snapshot for next iteration
		newProcCPU[pid] = &ProcessCPUSnapshot{
			PID:       pid,
			Timestamp: now,
			UTime:     p.Stat.UTime,
			STime:     p.Stat.STime,
		}

		state := string(p.Stat.State)
		if state == "" {
			state = "?"
		}

		cgroupPath := ""
		if p.Cgroup != nil {
			cgroupPath = p.Cgroup.Path
		}

		metrics = append(metrics, ProcessMetrics{
			PID:        pid,
			Name:       p.Status.Name,
			CPUPercent: cpuPercent,
			MemRSS:     p.Status.VmRSS,
			MemVirtual: p.Status.VmSize,
			Threads:    p.Status.Threads,
			State:      state,
			CgroupPath: cgroupPath,
		})
	}

	// Update process CPU snapshots for next iteration
	a.prevProcCPU = newProcCPU

	return metrics
}

// calculateMemoryMetrics calculates aggregated memory metrics
func (a *Aggregator) calculateMemoryMetrics(sysInfo *proc.SystemInfo, processes []ProcessMetrics) MemoryMetrics {
	var totalRSS uint64
	for _, p := range processes {
		totalRSS += p.MemRSS
	}

	usedBytes := sysInfo.MemTotal - sysInfo.MemAvailable
	usedPercent := 0.0
	rssPercent := 0.0

	if sysInfo.MemTotal > 0 {
		usedPercent = float64(usedBytes) / float64(sysInfo.MemTotal) * 100
		rssPercent = float64(totalRSS) / float64(sysInfo.MemTotal) * 100
	}

	return MemoryMetrics{
		TotalBytes:     sysInfo.MemTotal,
		UsedBytes:      usedBytes,
		FreeBytes:      sysInfo.MemFree,
		AvailableBytes: sysInfo.MemAvailable,
		UsedPercent:    usedPercent,
		TotalRSSBytes:  totalRSS,
		RSSPercent:     rssPercent,
	}
}

// getTopByMetric returns the top N processes by a given metric
func (a *Aggregator) getTopByMetric(metrics []ProcessMetrics, getValue func(ProcessMetrics) float64) []ProcessMetrics {
	if len(metrics) == 0 {
		return nil
	}

	// Sort by the metric value (descending)
	sorted := make([]ProcessMetrics, len(metrics))
	copy(sorted, metrics)
	sort.Slice(sorted, func(i, j int) bool {
		return getValue(sorted[i]) > getValue(sorted[j])
	})

	// Return top N
	n := a.topN
	if n > len(sorted) {
		n = len(sorted)
	}

	return sorted[:n]
}

// discoverCgroupMappings discovers cgroup path to container name mappings
// by looking for processes that match the configured process mapping.
func (a *Aggregator) discoverCgroupMappings(processes []*proc.ProcessInfo) {
	if len(a.processMapping) == 0 {
		return
	}

	for _, p := range processes {
		if p.Cgroup == nil || p.Cgroup.Path == "" {
			continue
		}

		// Check if this process name is in our mapping
		if containerName, ok := a.processMapping[p.Status.Name]; ok {
			// Map this cgroup path to the container name
			a.cgroupPathMapping[p.Cgroup.Path] = containerName
		}
	}
}

// resolveContainerName returns the container name for a cgroup path,
// or the raw path if no mapping exists.
func (a *Aggregator) resolveContainerName(cgroupPath string) string {
	if name, ok := a.cgroupPathMapping[cgroupPath]; ok {
		return name
	}
	// Use raw path as fallback
	if cgroupPath == "" {
		return "<unknown>"
	}
	return cgroupPath
}

// calculateCgroupMetrics computes metrics grouped by container/cgroup.
func (a *Aggregator) calculateCgroupMetrics(
	processes []*proc.ProcessInfo,
	processMetrics []ProcessMetrics,
	now time.Time,
) map[string]*CgroupMetrics {
	// Build lookup from PID to ProcessMetrics
	pmByPID := make(map[int]ProcessMetrics)
	for _, pm := range processMetrics {
		pmByPID[pm.PID] = pm
	}

	// Group processes by container name
	type cgroupData struct {
		cgroupPath string
		procs      []*proc.ProcessInfo
		metrics    []ProcessMetrics
	}
	containerGroups := make(map[string]*cgroupData)

	for _, p := range processes {
		cgroupPath := ""
		if p.Cgroup != nil {
			cgroupPath = p.Cgroup.Path
		}

		containerName := a.resolveContainerName(cgroupPath)

		if _, ok := containerGroups[containerName]; !ok {
			containerGroups[containerName] = &cgroupData{
				cgroupPath: cgroupPath,
			}
		}

		containerGroups[containerName].procs = append(containerGroups[containerName].procs, p)

		if pm, ok := pmByPID[p.Stat.PID]; ok {
			containerGroups[containerName].metrics = append(containerGroups[containerName].metrics, pm)
		}
	}

	// Calculate elapsed time since last collection
	elapsed := 0.0
	if !a.prevCgroupTime.IsZero() {
		elapsed = now.Sub(a.prevCgroupTime).Seconds()
	}
	a.prevCgroupTime = now

	// Calculate metrics for each container
	result := make(map[string]*CgroupMetrics)

	for containerName, data := range containerGroups {
		// Sum CPU ticks (utime + stime only, not cutime/cstime)
		var totalTicks uint64
		var totalRSS uint64

		for _, p := range data.procs {
			totalTicks += p.Stat.TotalTime()
			totalRSS += p.Status.VmRSS
		}

		// Calculate CPU cores used from delta
		usedCores := 0.0
		hasDelta := false
		if prev, ok := a.prevCgroupCPU[containerName]; ok && elapsed > 0 {
			// Guard against underflow: if processes exited and new ones started,
			// totalTicks could be less than prev. In that case, skip this sample.
			if totalTicks >= prev {
				deltaTicks := totalTicks - prev
				// Convert ticks to cores: deltaTicks / (elapsed_seconds * CLK_TCK)
				usedCores = float64(deltaTicks) / (elapsed * float64(proc.DefaultClockTicks))
				hasDelta = true
			}
		}
		a.prevCgroupCPU[containerName] = totalTicks

		// Calculate percentages against limits if available
		cpuPercent := 0.0
		memPercent := 0.0
		var limitCores float64
		var limitBytes uint64

		if limit, ok := a.cgroupLimits[containerName]; ok {
			limitCores = limit.CPUCores
			limitBytes = limit.MemoryBytes
			if limit.CPUCores > 0 {
				cpuPercent = (usedCores / limit.CPUCores) * 100
			}
			if limit.MemoryBytes > 0 {
				memPercent = (float64(totalRSS) / float64(limit.MemoryBytes)) * 100
			}
		}

		result[containerName] = &CgroupMetrics{
			Name:       containerName,
			CgroupPath: data.cgroupPath,
			CPU: CgroupCPUMetrics{
				TotalTicks:  totalTicks,
				UsedCores:   usedCores,
				UsedPercent: cpuPercent,
				LimitCores:  limitCores,
				HasDelta:    hasDelta,
			},
			Memory: CgroupMemoryMetrics{
				TotalRSSBytes: totalRSS,
				UsedPercent:   memPercent,
				LimitBytes:    limitBytes,
			},
			Processes: data.metrics,
			NumProcs:  len(data.procs),
		}
	}

	return result
}