package api

import (
	"bytes"
	"context"
	"fmt"
	"net/http"
	"os"
	"runtime/pprof"
	"time"

	"github.com/safing/portbase/utils/debug"
)

func registerDebugEndpoints() error {
	if err := RegisterEndpoint(Endpoint{
		Path:        "ping",
		Read:        PermitAnyone,
		ActionFunc:  ping,
		Name:        "Ping",
		Description: "Pong.",
	}); err != nil {
		return err
	}

	if err := RegisterEndpoint(Endpoint{
		Path:        "debug/stack",
		Read:        PermitAnyone,
		DataFunc:    getStack,
		Name:        "Get Goroutine Stack",
		Description: "Returns the current goroutine stack.",
	}); err != nil {
		return err
	}

	if err := RegisterEndpoint(Endpoint{
		Path:        "debug/stack/print",
		Read:        PermitAnyone,
		ActionFunc:  printStack,
		Name:        "Print Goroutine Stack",
		Description: "Prints the current goroutine stack to stdout.",
	}); err != nil {
		return err
	}

	if err := RegisterEndpoint(Endpoint{
		Path:        "debug/cpu",
		Read:        PermitAnyone,
		DataFunc:    handleCPUProfile,
		Name:        "Get CPU Profile",
		Description: "",
		Parameters: []Parameter{{
			Method:      http.MethodGet,
			Field:       "duration",
			Value:       "10s",
			Description: "Specify the formatting style. The default is simple markdown formatting.",
		}},
	}); err != nil {
		return err
	}

	if err := RegisterEndpoint(Endpoint{
		Path:        "debug/heap",
		Read:        PermitAnyone,
		DataFunc:    handleHeapProfile,
		Name:        "Get Heap Profile",
		Description: "",
	}); err != nil {
		return err
	}

	if err := RegisterEndpoint(Endpoint{
		Path:        "debug/allocs",
		Read:        PermitAnyone,
		DataFunc:    handleAllocsProfile,
		Name:        "Get Allocs Profile",
		Description: "",
	}); err != nil {
		return err
	}

	if err := RegisterEndpoint(Endpoint{
		Path:        "debug/info",
		Read:        PermitAnyone,
		DataFunc:    debugInfo,
		Name:        "Get Debug Information",
		Description: "Returns debugging information, including the version and platform info, errors, logs and the current goroutine stack.",
		Parameters: []Parameter{{
			Method:      http.MethodGet,
			Field:       "style",
			Value:       "github",
			Description: "Specify the formatting style. The default is simple markdown formatting.",
		}},
	}); err != nil {
		return err
	}

	return nil
}

// ping responds with pong.
func ping(ar *Request) (msg string, err error) {
	return "Pong.", nil
}

// getStack returns the current goroutine stack.
func getStack(_ *Request) (data []byte, err error) {
	buf := &bytes.Buffer{}
	err = pprof.Lookup("goroutine").WriteTo(buf, 1)
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

// printStack prints the current goroutine stack to stderr.
func printStack(_ *Request) (msg string, err error) {
	_, err = fmt.Fprint(os.Stderr, "===== PRINTING STACK =====\n")
	if err == nil {
		err = pprof.Lookup("goroutine").WriteTo(os.Stderr, 1)
	}
	if err == nil {
		_, err = fmt.Fprint(os.Stderr, "===== END OF STACK =====\n")
	}
	if err != nil {
		return "", err
	}
	return "stack printed to stdout", nil
}

// handleCPUProfile returns the CPU profile.
func handleCPUProfile(ar *Request) (data []byte, err error) {
	// Parse duration.
	duration := 10 * time.Second
	if durationOption := ar.Request.URL.Query().Get("duration"); durationOption != "" {
		parsedDuration, err := time.ParseDuration(durationOption)
		if err != nil {
			return nil, fmt.Errorf("failed to parse duration: %w", err)
		}
		duration = parsedDuration
	}

	// Start CPU profiling.
	buf := new(bytes.Buffer)
	if err := pprof.StartCPUProfile(buf); err != nil {
		return nil, fmt.Errorf("failed to start cpu profile: %w", err)
	}

	// Wait for the specified duration.
	select {
	case <-time.After(duration):
	case <-ar.Context().Done():
		pprof.StopCPUProfile()
		return nil, context.Canceled
	}

	// Stop CPU profiling and return data.
	pprof.StopCPUProfile()
	return buf.Bytes(), nil
}

// handleHeapProfile returns the Heap profile.
func handleHeapProfile(ar *Request) (data []byte, err error) {
	buf := new(bytes.Buffer)
	if err := pprof.Lookup("heap").WriteTo(buf, 0); err != nil {
		return nil, fmt.Errorf("failed to write heap profile: %w", err)
	}
	return buf.Bytes(), nil
}

// handleAllocsProfile returns the Allocs profile.
func handleAllocsProfile(ar *Request) (data []byte, err error) {
	buf := new(bytes.Buffer)
	if err := pprof.Lookup("allocs").WriteTo(buf, 0); err != nil {
		return nil, fmt.Errorf("failed to write allocs profile: %w", err)
	}
	return buf.Bytes(), nil
}

// debugInfo returns the debugging information for support requests.
func debugInfo(ar *Request) (data []byte, err error) {
	// Create debug information helper.
	di := new(debug.Info)
	di.Style = ar.Request.URL.Query().Get("style")

	// Add debug information.
	di.AddVersionInfo()
	di.AddPlatformInfo(ar.Context())
	di.AddLastReportedModuleError()
	di.AddLastUnexpectedLogs()
	di.AddGoroutineStack()

	// Return data.
	return di.Bytes(), nil
}