package api

import (
	"encoding/json"
	"net/http"
	"time"

	"github.com/rs/zerolog/log"

	"github.com/rcourtman/pulse-go-rewrite/internal/unifiedresources"
)

// MonitoredSystemLedgerEntry represents a single counted top-level monitored
// system.
type MonitoredSystemLedgerEntry struct {
	Name                 string                                 `json:"name"`
	Type                 string                                 `json:"type"`
	Status               string                                 `json:"status"` // "online", "warning", "offline", "unknown"
	StatusExplanation    MonitoredSystemLedgerStatusExplanation `json:"status_explanation"`
	LatestIncludedSignal MonitoredSystemLedgerLatestSignal      `json:"latest_included_signal"`
	Source               string                                 `json:"source"`
	Explanation          MonitoredSystemLedgerExplanation       `json:"explanation"`
}

type MonitoredSystemLedgerLatestSignal struct {
	Name   string `json:"name"`
	Type   string `json:"type"`
	Source string `json:"source"`
	At     string `json:"at"`
}

type MonitoredSystemLedgerStatusExplanation struct {
	Summary string                              `json:"summary"`
	Reasons []MonitoredSystemLedgerStatusReason `json:"reasons"`
}

type MonitoredSystemLedgerStatusReason struct {
	Kind       string `json:"kind"`
	Name       string `json:"name"`
	Type       string `json:"type"`
	Source     string `json:"source"`
	Status     string `json:"status"`
	ReportedAt string `json:"reported_at"`
	Summary    string `json:"summary"`
}

type MonitoredSystemLedgerExplanation struct {
	Summary  string                                    `json:"summary"`
	Reasons  []MonitoredSystemLedgerExplanationReason  `json:"reasons"`
	Surfaces []MonitoredSystemLedgerExplanationSurface `json:"surfaces"`
}

type MonitoredSystemLedgerExplanationReason struct {
	Kind    string `json:"kind"`
	Signal  string `json:"signal"`
	Summary string `json:"summary"`
}

type MonitoredSystemLedgerExplanationSurface struct {
	Name   string `json:"name"`
	Type   string `json:"type"`
	Source string `json:"source"`
}

// MonitoredSystemLedgerResponse is the response for GET /api/license/monitored-system-ledger.
type MonitoredSystemLedgerResponse struct {
	Systems []MonitoredSystemLedgerEntry `json:"systems"`
	Total   int                          `json:"total"`
	Limit   int                          `json:"limit"` // 0 = unlimited
}

func EmptyMonitoredSystemLedgerResponse() MonitoredSystemLedgerResponse {
	return MonitoredSystemLedgerResponse{}.NormalizeCollections()
}

func (r MonitoredSystemLedgerResponse) NormalizeCollections() MonitoredSystemLedgerResponse {
	if r.Systems == nil {
		r.Systems = []MonitoredSystemLedgerEntry{}
	}
	for i := range r.Systems {
		r.Systems[i] = r.Systems[i].NormalizeCollections()
	}
	return r
}

func (e MonitoredSystemLedgerEntry) NormalizeCollections() MonitoredSystemLedgerEntry {
	if e.LatestIncludedSignal.Name == "" {
		e.LatestIncludedSignal.Name = "Unnamed source"
	}
	if e.LatestIncludedSignal.Type == "" {
		e.LatestIncludedSignal.Type = "system"
	}
	if e.StatusExplanation.Reasons == nil {
		e.StatusExplanation.Reasons = []MonitoredSystemLedgerStatusReason{}
	}
	if e.Explanation.Reasons == nil {
		e.Explanation.Reasons = []MonitoredSystemLedgerExplanationReason{}
	}
	if e.Explanation.Surfaces == nil {
		e.Explanation.Surfaces = []MonitoredSystemLedgerExplanationSurface{}
	}
	return e
}

func (r *Router) handleMonitoredSystemLedger(w http.ResponseWriter, req *http.Request) {
	orgID := GetOrgID(req.Context())

	// Get canonical monitored systems from the unified ReadState surface.
	var systems []unifiedresources.MonitoredSystemRecord
	var monitorResolved bool
	if r.mtMonitor != nil {
		monitor, monErr := r.mtMonitor.GetMonitor(orgID)
		if monErr != nil {
			log.Warn().Err(monErr).Str("org", orgID).Msg("monitored-system-ledger: failed to resolve tenant monitor")
		}
		if monitor != nil {
			if rs := monitor.GetUnifiedReadState(); rs != nil {
				systems = unifiedresources.MonitoredSystems(rs)
			}
			monitorResolved = true
		}
	}
	// Fallback to the default monitor only for the default org to avoid cross-tenant data leaks.
	if !monitorResolved && orgID == "default" && r.monitor != nil {
		if rs := r.monitor.GetUnifiedReadState(); rs != nil {
			systems = unifiedresources.MonitoredSystems(rs)
		}
	}

	entries := make([]MonitoredSystemLedgerEntry, 0, len(systems))
	for _, system := range systems {
		entries = append(entries, monitoredSystemLedgerEntry(system))
	}

	limit := maxMonitoredSystemsLimitForContext(req.Context())

	resp := EmptyMonitoredSystemLedgerResponse()
	resp.Systems = entries
	resp.Total = len(entries)
	resp.Limit = limit

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp.NormalizeCollections())
}

func monitoredSystemLedgerEntry(system unifiedresources.MonitoredSystemRecord) MonitoredSystemLedgerEntry {
	status := normalizeStatus(string(system.Status))
	latestIncludedSignal := monitoredSystemLedgerLatestSignal(system.LatestIncludedSignal)
	return MonitoredSystemLedgerEntry{
		Name:                 system.Name,
		Type:                 system.Type,
		Status:               status,
		StatusExplanation:    monitoredSystemLedgerStatusExplanation(system.StatusExplanation, status),
		LatestIncludedSignal: latestIncludedSignal,
		Source:               system.Source,
		Explanation:          monitoredSystemLedgerExplanation(system.Explanation),
	}
}

// ---------------------------------------------------------------------------
// Status helpers
// ---------------------------------------------------------------------------

func normalizeStatus(s string) string {
	switch s {
	case "online", "warning", "offline", "unknown":
		return s
	default:
		return "unknown"
	}
}

func monitoredSystemLedgerStatusExplanation(
	explanation unifiedresources.MonitoredSystemStatusExplanation,
	status string,
) MonitoredSystemLedgerStatusExplanation {
	reasons := make([]MonitoredSystemLedgerStatusReason, 0, len(explanation.Reasons))
	for _, reason := range explanation.Reasons {
		reasons = append(reasons, MonitoredSystemLedgerStatusReason{
			Kind:       reason.Kind,
			Name:       reason.Name,
			Type:       reason.Type,
			Source:     reason.Source,
			Status:     normalizeMonitoredSystemLedgerReasonStatus(reason.Status),
			ReportedAt: formatMonitoredSystemTime(reason.ReportedAt),
			Summary:    reason.Summary,
		})
	}

	summary := explanation.Summary
	if summary == "" {
		summary = defaultMonitoredSystemLedgerStatusSummary(status)
	}

	return MonitoredSystemLedgerStatusExplanation{
		Summary: summary,
		Reasons: reasons,
	}
}

func defaultMonitoredSystemLedgerStatusSummary(status string) string {
	switch status {
	case "online":
		return "All included top-level collection paths currently report online status."
	case "warning":
		return "At least one included top-level collection path is degraded, so Pulse marks this monitored system as warning."
	case "offline":
		return "At least one included source is offline or disconnected, so Pulse marks this monitored system as offline."
	default:
		return "Pulse cannot determine a canonical runtime status for this monitored system yet."
	}
}

func normalizeMonitoredSystemLedgerReasonStatus(status string) string {
	switch status {
	case "online", "stale", "offline", "unknown":
		return status
	default:
		return "unknown"
	}
}

func normalizeMonitoredSystemLedgerSource(source string) string {
	switch source {
	case "agent", "docker", "kubernetes", "pbs", "pmg", "proxmox", "truenas":
		return source
	default:
		return ""
	}
}

func monitoredSystemLedgerLatestSignal(
	signal unifiedresources.MonitoredSystemLatestSignal,
) MonitoredSystemLedgerLatestSignal {
	return MonitoredSystemLedgerLatestSignal{
		Name:   signal.Name,
		Type:   signal.Type,
		Source: normalizeMonitoredSystemLedgerSource(signal.Source),
		At:     formatMonitoredSystemTime(signal.At),
	}
}

func formatMonitoredSystemTime(t time.Time) string {
	if t.IsZero() {
		return ""
	}
	return t.UTC().Format(time.RFC3339)
}

func monitoredSystemLedgerExplanation(
	explanation unifiedresources.MonitoredSystemGroupingExplanation,
) MonitoredSystemLedgerExplanation {
	reasons := make([]MonitoredSystemLedgerExplanationReason, 0, len(explanation.Reasons))
	for _, reason := range explanation.Reasons {
		reasons = append(reasons, MonitoredSystemLedgerExplanationReason{
			Kind:    reason.Kind,
			Signal:  reason.Signal,
			Summary: reason.Summary,
		})
	}

	surfaces := make([]MonitoredSystemLedgerExplanationSurface, 0, len(explanation.Surfaces))
	for _, surface := range explanation.Surfaces {
		surfaces = append(surfaces, MonitoredSystemLedgerExplanationSurface{
			Name:   surface.Name,
			Type:   surface.Type,
			Source: surface.Source,
		})
	}

	return MonitoredSystemLedgerExplanation{
		Summary:  explanation.Summary,
		Reasons:  reasons,
		Surfaces: surfaces,
	}
}