package coderd

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"runtime"
	"runtime/pprof"
	"runtime/trace"
	"slices"
	"strings"
	"time"

	"github.com/google/uuid"
	"golang.org/x/xerrors"

	"cdr.dev/slog/v3"
	"github.com/coder/coder/v2/coderd/audit"
	"github.com/coder/coder/v2/coderd/database"
	"github.com/coder/coder/v2/coderd/httpapi"
	"github.com/coder/coder/v2/coderd/httpmw"
	"github.com/coder/coder/v2/coderd/rbac"
	"github.com/coder/coder/v2/coderd/rbac/policy"
	"github.com/coder/coder/v2/coderd/util/slice"
	"github.com/coder/coder/v2/codersdk"
	"github.com/coder/coder/v2/codersdk/healthsdk"
)

// @Summary Debug Info Wireguard Coordinator
// @ID debug-info-wireguard-coordinator
// @Security CoderSessionToken
// @Produce text/html
// @Tags Debug
// @Success 200
// @Router /debug/coordinator [get]
func (api *API) debugCoordinator(rw http.ResponseWriter, r *http.Request) {
	(*api.TailnetCoordinator.Load()).ServeHTTPDebug(rw, r)
}

// @Summary Debug Info Tailnet
// @ID debug-info-tailnet
// @Security CoderSessionToken
// @Produce text/html
// @Tags Debug
// @Success 200
// @Router /debug/tailnet [get]
func (api *API) debugTailnet(rw http.ResponseWriter, r *http.Request) {
	api.agentProvider.ServeHTTPDebug(rw, r)
}

// @Summary Debug Info Deployment Health
// @ID debug-info-deployment-health
// @Security CoderSessionToken
// @Produce json
// @Tags Debug
// @Success 200 {object} healthsdk.HealthcheckReport
// @Router /debug/health [get]
// @Param force query boolean false "Force a healthcheck to run"
func (api *API) debugDeploymentHealth(rw http.ResponseWriter, r *http.Request) {
	apiKey := httpmw.APITokenFromRequest(r)
	ctx, cancel := context.WithTimeout(r.Context(), api.Options.HealthcheckTimeout)
	defer cancel()

	// Load sections previously marked as dismissed.
	// We hydrate this here as we cache the healthcheck and hydrating in the
	// healthcheck function itself can lead to stale results.
	dismissed := loadDismissedHealthchecks(ctx, api.Database, api.Logger)

	// Check if the forced query parameter is set.
	forced := r.URL.Query().Get("force") == "true"

	// Get cached report if it exists and the requester did not force a refresh.
	if !forced {
		if report := api.healthCheckCache.Load(); report != nil {
			if time.Since(report.Time) < api.Options.HealthcheckRefresh {
				formatHealthcheck(ctx, rw, r, *report, dismissed...)
				return
			}
		}
	}

	resChan := api.healthCheckGroup.DoChan("", func() (*healthsdk.HealthcheckReport, error) {
		// Create a new context not tied to the request.
		ctx, cancel := context.WithTimeout(context.Background(), api.Options.HealthcheckTimeout)
		defer cancel()

		// Create and store progress tracker for timeout diagnostics.
		report := api.HealthcheckFunc(ctx, apiKey, &api.healthCheckProgress)
		if report != nil { // Only store non-nil reports.
			api.healthCheckCache.Store(report)
		}
		api.healthCheckProgress.Reset()
		return report, nil
	})

	select {
	case <-ctx.Done():
		summary := api.healthCheckProgress.Summary()
		httpapi.Write(ctx, rw, http.StatusServiceUnavailable, codersdk.Response{
			Message: "Healthcheck timed out.",
			Detail:  summary,
		})
		return
	case res := <-resChan:
		report := res.Val
		if report == nil {
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "There was an unknown error completing the healthcheck.",
				Detail:  "nil report from healthcheck result channel",
			})
			return
		}
		formatHealthcheck(ctx, rw, r, *report, dismissed...)
		return
	}
}

func formatHealthcheck(ctx context.Context, rw http.ResponseWriter, r *http.Request, hc healthsdk.HealthcheckReport, dismissed ...healthsdk.HealthSection) {
	// Mark any sections previously marked as dismissed.
	for _, d := range dismissed {
		switch d {
		case healthsdk.HealthSectionAccessURL:
			hc.AccessURL.Dismissed = true
		case healthsdk.HealthSectionDERP:
			hc.DERP.Dismissed = true
		case healthsdk.HealthSectionDatabase:
			hc.Database.Dismissed = true
		case healthsdk.HealthSectionWebsocket:
			hc.Websocket.Dismissed = true
		case healthsdk.HealthSectionWorkspaceProxy:
			hc.WorkspaceProxy.Dismissed = true
		}
	}

	format := r.URL.Query().Get("format")
	switch format {
	case "text":
		rw.Header().Set("Content-Type", "text/plain; charset=utf-8")
		rw.WriteHeader(http.StatusOK)

		_, _ = fmt.Fprintln(rw, "time:", hc.Time.Format(time.RFC3339))
		_, _ = fmt.Fprintln(rw, "healthy:", hc.Healthy)
		_, _ = fmt.Fprintln(rw, "derp:", hc.DERP.Healthy)
		_, _ = fmt.Fprintln(rw, "access_url:", hc.AccessURL.Healthy)
		_, _ = fmt.Fprintln(rw, "websocket:", hc.Websocket.Healthy)
		_, _ = fmt.Fprintln(rw, "database:", hc.Database.Healthy)

	case "", "json":
		httpapi.WriteIndent(ctx, rw, http.StatusOK, hc)

	default:
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: fmt.Sprintf("Invalid format option %q.", format),
			Detail:  "Allowed values are: \"json\", \"simple\".",
		})
	}
}

// @Summary Get health settings
// @ID get-health-settings
// @Security CoderSessionToken
// @Produce json
// @Tags Debug
// @Success 200 {object} healthsdk.HealthSettings
// @Router /debug/health/settings [get]
func (api *API) deploymentHealthSettings(rw http.ResponseWriter, r *http.Request) {
	settingsJSON, err := api.Database.GetHealthSettings(r.Context())
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to fetch health settings.",
			Detail:  err.Error(),
		})
		return
	}

	var settings healthsdk.HealthSettings
	err = json.Unmarshal([]byte(settingsJSON), &settings)
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to unmarshal health settings.",
			Detail:  err.Error(),
		})
		return
	}

	if len(settings.DismissedHealthchecks) == 0 {
		settings.DismissedHealthchecks = []healthsdk.HealthSection{}
	}

	httpapi.Write(r.Context(), rw, http.StatusOK, settings)
}

// @Summary Update health settings
// @ID update-health-settings
// @Security CoderSessionToken
// @Accept json
// @Produce json
// @Tags Debug
// @Param request body healthsdk.UpdateHealthSettings true "Update health settings"
// @Success 200 {object} healthsdk.UpdateHealthSettings
// @Router /debug/health/settings [put]
func (api *API) putDeploymentHealthSettings(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	if !api.Authorize(r, policy.ActionUpdate, rbac.ResourceDeploymentConfig) {
		httpapi.Write(ctx, rw, http.StatusForbidden, codersdk.Response{
			Message: "Insufficient permissions to update health settings.",
		})
		return
	}

	var settings healthsdk.HealthSettings
	if !httpapi.Read(ctx, rw, r, &settings) {
		return
	}

	err := validateHealthSettings(settings)
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to validate health settings.",
			Detail:  err.Error(),
		})
		return
	}

	settingsJSON, err := json.Marshal(&settings)
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to marshal health settings.",
			Detail:  err.Error(),
		})
		return
	}

	currentSettingsJSON, err := api.Database.GetHealthSettings(r.Context())
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to fetch current health settings.",
			Detail:  err.Error(),
		})
		return
	}

	if bytes.Equal(settingsJSON, []byte(currentSettingsJSON)) {
		// See: https://www.rfc-editor.org/rfc/rfc7231#section-6.3.5
		rw.WriteHeader(http.StatusNoContent)
		return
	}

	auditor := api.Auditor.Load()
	aReq, commitAudit := audit.InitRequest[database.HealthSettings](rw, &audit.RequestParams{
		Audit:   *auditor,
		Log:     api.Logger,
		Request: r,
		Action:  database.AuditActionWrite,
	})
	defer commitAudit()

	aReq.New = database.HealthSettings{
		ID:                    uuid.New(),
		DismissedHealthchecks: slice.ToStrings(settings.DismissedHealthchecks),
	}

	err = api.Database.UpsertHealthSettings(ctx, string(settingsJSON))
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to update health settings.",
			Detail:  err.Error(),
		})
		return
	}

	httpapi.Write(r.Context(), rw, http.StatusOK, settings)
}

func validateHealthSettings(settings healthsdk.HealthSettings) error {
	for _, dismissed := range settings.DismissedHealthchecks {
		ok := slices.Contains(healthsdk.HealthSections, dismissed)
		if !ok {
			return xerrors.Errorf("unknown healthcheck section: %s", dismissed)
		}
	}
	return nil
}

// For some reason the swagger docs need to be attached to a function.

// @Summary Debug Info Websocket Test
// @ID debug-info-websocket-test
// @Security CoderSessionToken
// @Produce json
// @Tags Debug
// @Success 201 {object} codersdk.Response
// @Router /debug/ws [get]
// @x-apidocgen {"skip": true}
func _debugws(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug DERP traffic
// @ID debug-derp-traffic
// @Security CoderSessionToken
// @Produce json
// @Success 200 {array} derp.BytesSentRecv
// @Tags Debug
// @Router /debug/derp/traffic [get]
// @x-apidocgen {"skip": true}
func _debugDERPTraffic(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug expvar
// @ID debug-expvar
// @Security CoderSessionToken
// @Produce json
// @Tags Debug
// @Success 200 {object} map[string]any
// @Router /debug/expvar [get]
// @x-apidocgen {"skip": true}
func _debugExpVar(http.ResponseWriter, *http.Request) {} //nolint:unused

func loadDismissedHealthchecks(ctx context.Context, db database.Store, logger slog.Logger) []healthsdk.HealthSection {
	dismissedHealthchecks := []healthsdk.HealthSection{}
	settingsJSON, err := db.GetHealthSettings(ctx)
	if err == nil {
		var settings healthsdk.HealthSettings
		err = json.Unmarshal([]byte(settingsJSON), &settings)
		if len(settings.DismissedHealthchecks) > 0 {
			dismissedHealthchecks = settings.DismissedHealthchecks
		}
	}
	if err != nil && !xerrors.Is(err, sql.ErrNoRows) {
		logger.Error(ctx, "unable to fetch health settings", slog.Error(err))
	}
	return dismissedHealthchecks
}

// ProfileCollector abstracts the mechanics of collecting pprof/trace
// data from the Go runtime. Production code uses defaultProfileCollector;
// tests can substitute a stub to avoid process-global side-effects.
type ProfileCollector interface {
	// StartCPUProfile begins CPU profiling, writing to w. It returns
	// a stop function that must be called to finish profiling.
	StartCPUProfile(w io.Writer) (stop func(), err error)
	// StartTrace begins execution tracing, writing to w. It returns
	// a stop function that must be called to finish tracing.
	StartTrace(w io.Writer) (stop func(), err error)
	// LookupProfile writes the named snapshot profile to w.
	LookupProfile(name string, w io.Writer) error
	// SetBlockProfileRate enables/disables block profiling.
	SetBlockProfileRate(rate int)
	// SetMutexProfileFraction enables/disables mutex profiling.
	// Returns the previous fraction.
	SetMutexProfileFraction(rate int) int
}

// defaultProfileCollector delegates to the real runtime/pprof and
// runtime/trace packages.
type defaultProfileCollector struct{}

func (defaultProfileCollector) StartCPUProfile(w io.Writer) (func(), error) {
	if err := pprof.StartCPUProfile(w); err != nil {
		return nil, err
	}
	return pprof.StopCPUProfile, nil
}

func (defaultProfileCollector) StartTrace(w io.Writer) (func(), error) {
	if err := trace.Start(w); err != nil {
		return nil, err
	}
	return trace.Stop, nil
}

func (defaultProfileCollector) LookupProfile(name string, w io.Writer) error {
	p := pprof.Lookup(name)
	if p == nil {
		return nil
	}
	return p.WriteTo(w, 0)
}

func (defaultProfileCollector) SetBlockProfileRate(rate int) { runtime.SetBlockProfileRate(rate) }
func (defaultProfileCollector) SetMutexProfileFraction(rate int) int {
	return runtime.SetMutexProfileFraction(rate)
}

// defaultProfiles is the set of profiles collected when none are specified.
var defaultProfiles = []string{"cpu", "heap", "allocs", "block", "mutex", "goroutine"}

// allValidProfiles enumerates every profile name accepted by the endpoint.
var allValidProfiles = map[string]bool{
	"cpu":          true,
	"heap":         true,
	"allocs":       true,
	"block":        true,
	"mutex":        true,
	"goroutine":    true,
	"threadcreate": true,
	"trace":        true,
}

const (
	// profileDurationDefault is used when no ?duration is supplied.
	profileDurationDefault = 10 * time.Second
	// profileDurationMax prevents callers from asking for arbitrarily long
	// collections that tie up the runtime-global CPU profiler.
	profileDurationMax = 60 * time.Second
)

// @Summary Collect debug profiles
// @ID collect-debug-profiles
// @Security CoderSessionToken
// @Tags Debug
// @Success 200
// @Router /debug/profile [post]
// @x-apidocgen {"skip": true}
func (api *API) debugCollectProfile(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Parse duration.
	duration := profileDurationDefault
	if v := r.URL.Query().Get("duration"); v != "" {
		d, err := time.ParseDuration(v)
		if err != nil {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Invalid duration parameter.",
				Detail:  err.Error(),
			})
			return
		}
		if d <= 0 {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Duration must be positive.",
			})
			return
		}
		if d > profileDurationMax {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: fmt.Sprintf("Duration cannot exceed %s.", profileDurationMax),
			})
			return
		}
		duration = d
	}

	// Parse requested profiles.
	profiles := defaultProfiles
	if v := r.URL.Query().Get("profiles"); v != "" {
		profiles = strings.Split(v, ",")
		for _, p := range profiles {
			if !allValidProfiles[p] {
				httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
					Message: fmt.Sprintf("Unknown profile type: %q.", p),
					Detail:  "Valid types: cpu, heap, allocs, block, mutex, goroutine, threadcreate, trace",
				})
				return
			}
		}
	}

	// Only one profile collection can run at a time because the CPU
	// profiler is process-global.
	if !api.ProfileCollecting.CompareAndSwap(false, true) {
		httpapi.Write(ctx, rw, http.StatusConflict, codersdk.Response{
			Message: "A profile collection is already in progress. Try again later.",
		})
		return
	}
	defer api.ProfileCollecting.Store(false)

	// Temporarily enable block and mutex profiling so those profiles are
	// actually populated. Restore previous values when we are done.
	// SetBlockProfileRate does not return the previous value, so we
	// simply disable it again after collection (the default is 0).
	pc := api.ProfileCollector
	pc.SetBlockProfileRate(1)
	prevMutexFraction := pc.SetMutexProfileFraction(1)
	defer pc.SetBlockProfileRate(0)
	defer pc.SetMutexProfileFraction(prevMutexFraction)

	// Determine which profiles need the timed collection (cpu, trace) vs
	// instant snapshots.
	wantCPU := false
	wantTrace := false
	for _, p := range profiles {
		switch p {
		case "cpu":
			wantCPU = true
		case "trace":
			wantTrace = true
		}
	}

	// Collect timed profiles (cpu and/or trace) for the requested
	// duration. StartCPUProfile and StartTrace each return a stop
	// function that must be called to finish collection.
	var cpuBuf, traceBuf bytes.Buffer
	var stopCPU, stopTrace func()
	if wantCPU {
		var err error
		stopCPU, err = pc.StartCPUProfile(&cpuBuf)
		if err != nil {
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "Failed to start CPU profile.",
				Detail:  err.Error(),
			})
			return
		}
	}
	if wantTrace {
		var err error
		stopTrace, err = pc.StartTrace(&traceBuf)
		if err != nil {
			if stopCPU != nil {
				stopCPU()
			}
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "Failed to start trace.",
				Detail:  err.Error(),
			})
			return
		}
	}

	if wantCPU || wantTrace {
		timer := api.Clock.NewTimer(duration, "debugCollectProfile")
		defer timer.Stop()
		select {
		case <-ctx.Done():
			if stopCPU != nil {
				stopCPU()
			}
			if stopTrace != nil {
				stopTrace()
			}
			// Client disconnected; nothing to write.
			return
		case <-timer.C:
		}
		if stopCPU != nil {
			stopCPU()
		}
		if stopTrace != nil {
			stopTrace()
		}
	}

	// Build the tar.gz archive.
	var archive bytes.Buffer
	gzw := gzip.NewWriter(&archive)
	tw := tar.NewWriter(gzw)

	addFile := func(name string, data []byte) error {
		hdr := &tar.Header{
			Name: name,
			Mode: 0o644,
			Size: int64(len(data)),
		}
		if err := tw.WriteHeader(hdr); err != nil {
			return xerrors.Errorf("write tar header for %s: %w", name, err)
		}
		if _, err := tw.Write(data); err != nil {
			return xerrors.Errorf("write tar data for %s: %w", name, err)
		}
		return nil
	}

	for _, p := range profiles {
		switch p {
		case "cpu":
			if err := addFile("cpu.prof", cpuBuf.Bytes()); err != nil {
				httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
					Message: "Failed to write CPU profile to archive.",
					Detail:  err.Error(),
				})
				return
			}
		case "trace":
			if err := addFile("trace.out", traceBuf.Bytes()); err != nil {
				httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
					Message: "Failed to write trace to archive.",
					Detail:  err.Error(),
				})
				return
			}
		default:
			// Snapshot profiles: heap, allocs, block, mutex, goroutine,
			// threadcreate.
			var buf bytes.Buffer
			if err := pc.LookupProfile(p, &buf); err != nil {
				httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
					Message: fmt.Sprintf("Failed to collect %s profile.", p),
					Detail:  err.Error(),
				})
				return
			}
			if err := addFile(p+".prof", buf.Bytes()); err != nil {
				httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
					Message: fmt.Sprintf("Failed to write %s profile to archive.", p),
					Detail:  err.Error(),
				})
				return
			}
		}
	}

	if err := tw.Close(); err != nil {
		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to finalize tar archive.",
			Detail:  err.Error(),
		})
		return
	}
	if err := gzw.Close(); err != nil {
		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to finalize gzip archive.",
			Detail:  err.Error(),
		})
		return
	}

	filename := fmt.Sprintf("coderd-profile-%d.tar.gz", time.Now().Unix())
	rw.Header().Set("Content-Type", "application/gzip")
	rw.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", filename))
	rw.WriteHeader(http.StatusOK)
	_, _ = rw.Write(archive.Bytes())
}

// @Summary Debug pprof index
// @ID debug-pprof-index
// @Security CoderSessionToken
// @Success 200
// @Tags Debug
// @Router /debug/pprof [get]
// @x-apidocgen {"skip": true}
func _debugPprofIndex(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug pprof cmdline
// @ID debug-pprof-cmdline
// @Security CoderSessionToken
// @Success 200
// @Tags Debug
// @Router /debug/pprof/cmdline [get]
// @x-apidocgen {"skip": true}
func _debugPprofCmdline(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug pprof profile
// @ID debug-pprof-profile
// @Security CoderSessionToken
// @Success 200
// @Tags Debug
// @Router /debug/pprof/profile [get]
// @x-apidocgen {"skip": true}
func _debugPprofProfile(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug pprof symbol
// @ID debug-pprof-symbol
// @Security CoderSessionToken
// @Success 200
// @Tags Debug
// @Router /debug/pprof/symbol [get]
// @x-apidocgen {"skip": true}
func _debugPprofSymbol(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug pprof trace
// @ID debug-pprof-trace
// @Security CoderSessionToken
// @Success 200
// @Tags Debug
// @Router /debug/pprof/trace [get]
// @x-apidocgen {"skip": true}
func _debugPprofTrace(http.ResponseWriter, *http.Request) {} //nolint:unused

// @Summary Debug metrics
// @ID debug-metrics
// @Security CoderSessionToken
// @Success 200
// @Tags Debug
// @Router /debug/metrics [get]
// @x-apidocgen {"skip": true}
func _debugMetrics(http.ResponseWriter, *http.Request) {} //nolint:unused