package proc

import (
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

type AMDReader struct {
	hwmonDir    string
	driver      string
	energyState map[string]EnergyState // tracks (path -> energy state) for energy*_input calculations
}

type EnergyState struct {
	lastEnergy uint64
	lastTime   time.Time
}

func NewAMDReader() (*AMDReader, error) {
	// Locate AMD k10temp or zenpower hwmon path
	matches, err := filepath.Glob("/sys/class/hwmon/hwmon*")
	if err != nil {
		return nil, err
	}

	for _, dir := range matches {
		b, err := os.ReadFile(filepath.Join(dir, "name"))
		if err != nil {
			continue
		}
		drv := strings.TrimSpace(string(b))
		if drv == "k10temp" || drv == "zenpower" {
			return &AMDReader{
				hwmonDir: dir,
				driver:   drv,
			}, nil
		}
	}

	return nil, fmt.Errorf("k10temp/zenpower driver not found under /sys/class/hwmon/")
}

func (r *AMDReader) ReadTemperatureSensors() ([]TempSensor, error) {
	inputs, err := filepath.Glob(filepath.Join(r.hwmonDir, "temp*_input"))
	if err != nil || len(inputs) == 0 {
		return nil, fmt.Errorf("no temperature inputs found in %s", r.hwmonDir)
	}

	temps := []TempSensor{}

	for _, inputPath := range inputs {
		valBytes, err := os.ReadFile(inputPath)
		if err != nil {
			continue
		}

		milliC, err := strconv.ParseFloat(strings.TrimSpace(string(valBytes)), 64)
		if err != nil {
			continue
		}

		labelPath := strings.TrimSuffix(inputPath, "_input") + "_label"
		label := ""
		if lBytes, err := os.ReadFile(labelPath); err == nil {
			label = strings.TrimSpace(string(lBytes))
		} else {
			label = filepath.Base(strings.TrimSuffix(inputPath, "_input"))
		}

		temps = append(temps, TempSensor{
			Name:  label,
			TempC: milliC / 1000.0,
		})
	}

	return temps, nil
}

func (r *AMDReader) ReadPowerSensors() ([]PowerSensor, error) {
	hwmonSensors := r.readHwmonPower()
	if len(hwmonSensors) > 0 {
		return hwmonSensors, nil
	}

	return r.readRaplPower(), nil
}

func (r *AMDReader) readHwmonPower() []PowerSensor {
	var powerSensors []PowerSensor

	getLabel := func(inputPath string) string {
		labelPath := strings.TrimSuffix(inputPath, "_input") + "_label"
		if lBytes, err := os.ReadFile(labelPath); err == nil {
			return strings.TrimSpace(string(lBytes))
		}
		return filepath.Base(strings.TrimSuffix(inputPath, "_input"))
	}

	powerInputs, _ := filepath.Glob(filepath.Join(r.hwmonDir, "power*_input"))
	for _, inputPath := range powerInputs {
		valBytes, err := os.ReadFile(inputPath)
		if err != nil {
			continue
		}

		microWatts, err := strconv.ParseFloat(strings.TrimSpace(string(valBytes)), 64)
		if err != nil {
			continue
		}

		powerSensors = append(powerSensors, PowerSensor{
			Name:  getLabel(inputPath),
			Watts: microWatts / 1_000_000.0,
		})
	}

	energyInputs, _ := filepath.Glob(filepath.Join(r.hwmonDir, "energy*_input"))
	if len(energyInputs) > 0 {
		r.calculateEnergyDelta(energyInputs, getLabel, &powerSensors)
	}

	return powerSensors
}

func (r *AMDReader) readRaplPower() []PowerSensor {
	var powerSensors []PowerSensor

	// Match both top-level and nested RAPL zone directories
	patterns := []string{
		"/sys/class/powercap/intel-rapl*/energy_uj",
		"/sys/class/powercap/intel-rapl/intel-rapl*/energy_uj",
		"/sys/class/powercap/intel-rapl/intel-rapl*/*/energy_uj",
	}

	var energyInputs []string
	seen := make(map[string]bool)

	for _, pattern := range patterns {
		matches, _ := filepath.Glob(pattern)
		for _, match := range matches {
			// Resolve symlinks to get real sysfs path
			realPath, err := filepath.EvalSymlinks(match)
			if err != nil {
				realPath = match
			}
			if !seen[realPath] {
				seen[realPath] = true
				energyInputs = append(energyInputs, realPath)
			}
		}
	}

	if len(energyInputs) == 0 {
		return powerSensors
	}

	getLabel := func(inputPath string) string {
		dir := filepath.Dir(inputPath)
		if nameBytes, err := os.ReadFile(filepath.Join(dir, "name")); err == nil {
			return strings.TrimSpace(string(nameBytes))
		}
		return filepath.Base(dir)
	}

	r.calculateEnergyDelta(energyInputs, getLabel, &powerSensors)
	return powerSensors
}

func (r *AMDReader) calculateEnergyDelta(inputs []string, getLabel func(string) string, out *[]PowerSensor) {
	now := time.Now()
	if r.energyState == nil {
		r.energyState = make(map[string]EnergyState)
	}

	for _, inputPath := range inputs {
		// Canonicalize path to resolve symlinks and prevent map key duplication
		realPath, err := filepath.EvalSymlinks(inputPath)
		if err != nil {
			realPath = inputPath
		}

		valBytes, err := os.ReadFile(realPath)
		if err != nil {
			continue
		}

		microJoules, err := strconv.ParseUint(strings.TrimSpace(string(valBytes)), 10, 64)
		if err != nil {
			continue
		}

		prevState, exists := r.energyState[realPath]
		r.energyState[realPath] = EnergyState{
			lastEnergy: microJoules,
			lastTime:   now,
		}

		// Initial seed step: power delta requires two distinct reads
		if !exists {
			continue
		}

		timeDiff := now.Sub(prevState.lastTime).Seconds()
		if timeDiff <= 0 {
			continue
		}

		maxRange := uint64(1<<64 - 1)
		rangeBytes, err := os.ReadFile(filepath.Join(filepath.Dir(realPath), "max_energy_range_uj"))
		if err == nil {
			if parsedMax, err := strconv.ParseUint(strings.TrimSpace(string(rangeBytes)), 10, 64); err == nil {
				maxRange = parsedMax
			}
		}

		var energyDiff uint64
		if microJoules >= prevState.lastEnergy {
			energyDiff = microJoules - prevState.lastEnergy
		} else {
			energyDiff = maxRange - prevState.lastEnergy + microJoules
		}

		watts := (float64(energyDiff) / 1_000_000.0) / timeDiff
		*out = append(*out, PowerSensor{
			Name:  getLabel(realPath),
			Watts: watts,
		})
	}
}