// Package agentapi is the in-guest controller's client for the host agent's per-guest local
// API (doc 03 §6, slice 8A). It reaches the agent over the bridge, pinning the agent's
// self-signed leaf by SHA-256 (the same pin convention the agent uses for the Proxmox/PBS host
// certs), and authenticates with the per-guest bearer token. In 8A it exercises GET /storage
// (connectivity + the controller learning its mounts); the full surface (the /backup/due
// quiesce loop) lands in 8B.
package agentapi

import (
	"bytes"
	"context"
	"crypto/sha256"
	"crypto/tls"
	"crypto/x509"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// Client talks to one agent local-API endpoint with a pinned leaf + bearer token.
type Client struct {
	baseURL string
	token   string
	hc      *http.Client
}

// MountInfo mirrors the agent's GET /storage mount entry (doc 03 §6).
type MountInfo struct {
	Key        string `json:"key"`
	Storage    string `json:"storage"`
	MountPoint string `json:"mount_point"`
	Class      string `json:"class"` // fast | slow | ""
	Backup     bool   `json:"backup"`
}

// StorageResponse mirrors the agent's GET /storage data payload.
type StorageResponse struct {
	VMID   int         `json:"vmid"`
	Mounts []MountInfo `json:"mounts"`
}

// apiResponse is the agent's {ok,data,error} envelope.
type apiResponse struct {
	OK    bool            `json:"ok"`
	Data  json.RawMessage `json:"data"`
	Error string          `json:"error"`
}

// New builds a pinned client for endpoint ("host:port") with the given per-guest token and the
// agent leaf-cert SHA-256 fingerprint (hex, ':'-separators tolerated). The pin is the trust
// anchor — the agent serves a self-signed cert, so chain verification is replaced by an exact
// leaf-DER SHA-256 match (fails closed on any mismatch).
func New(endpoint, token, fingerprintHex string) (*Client, error) {
	endpoint = strings.TrimSpace(endpoint)
	if endpoint == "" {
		return nil, fmt.Errorf("agentapi: endpoint required")
	}
	if token == "" {
		return nil, fmt.Errorf("agentapi: token required")
	}
	want, err := normalizeFingerprint(fingerprintHex)
	if err != nil {
		return nil, err
	}
	tlsCfg := &tls.Config{
		InsecureSkipVerify: true, // self-signed leaf — the pin below is the real check
		VerifyPeerCertificate: func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
			if len(rawCerts) == 0 {
				return fmt.Errorf("agentapi: TLS pin: peer presented no certificate")
			}
			got := sha256.Sum256(rawCerts[0]) // leaf DER
			if hex.EncodeToString(got[:]) != want {
				return fmt.Errorf("agentapi: TLS pin mismatch: agent leaf SHA-256 does not match the bootstrap fingerprint")
			}
			return nil
		},
		MinVersion: tls.VersionTLS12,
	}
	return &Client{
		baseURL: "https://" + endpoint,
		token:   token,
		hc: &http.Client{
			Timeout:   15 * time.Second,
			Transport: &http.Transport{TLSClientConfig: tlsCfg},
		},
	}, nil
}

// Storage calls GET /storage and returns this guest's mounts (connectivity + placement view).
func (c *Client) Storage(ctx context.Context) (StorageResponse, error) {
	var out StorageResponse
	body, err := c.get(ctx, "/storage")
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode /storage: %w", err)
	}
	return out, nil
}

// ---- slice 8B: app-consistent backup (quiesce loop) -------------------------------------

// DueResponse mirrors the agent's GET /backup/due payload.
type DueResponse struct {
	VMID   int    `json:"vmid"`
	Due    bool   `json:"due"`
	Reason string `json:"reason"`
}

// BackupResponse mirrors the agent's POST /backup payload.
type BackupResponse struct {
	VMID  int    `json:"vmid"`
	JobID string `json:"job_id"`
	Phase string `json:"phase"`
}

// StatusResponse mirrors the agent's GET /backup/status payload.
type StatusResponse struct {
	VMID  int    `json:"vmid"`
	Phase string `json:"phase"` // idle | running | done | failed
	JobID string `json:"job_id"`
	Error string `json:"error"`
}

// Backup status phases (mirror the agent's vocabulary).
const (
	PhaseIdle    = "idle"
	PhaseRunning = "running"
	PhaseDone    = "done"
	PhaseFailed  = "failed"
)

// BackupDue reports whether a policy-scheduled backup is due for this guest (the quiesce trigger).
func (c *Client) BackupDue(ctx context.Context) (DueResponse, error) {
	var out DueResponse
	body, err := c.get(ctx, "/backup/due")
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode /backup/due: %w", err)
	}
	return out, nil
}

// StartBackup enqueues a backup of this guest (the agent vzdump) and returns the job to poll.
func (c *Client) StartBackup(ctx context.Context) (BackupResponse, error) {
	var out BackupResponse
	body, err := c.post(ctx, "/backup", struct{}{})
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode POST /backup: %w", err)
	}
	return out, nil
}

// BackupStatus reports the current/last backup job phase for this guest.
func (c *Client) BackupStatus(ctx context.Context) (StatusResponse, error) {
	var out StatusResponse
	body, err := c.get(ctx, "/backup/status")
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode /backup/status: %w", err)
	}
	return out, nil
}

// ---- slice 8C: disk management (execution is the agent's) --------------------------------

// DiskInfo mirrors the agent's GET /disks entry.
type DiskInfo struct {
	Name          string `json:"name"`
	Type          string `json:"type"`
	State         string `json:"state"`
	BackingDevice string `json:"backing_device"`
	MountPath     string `json:"mount_path"`
	Class         string `json:"class"`
	// Role is the agent's AUTHORITATIVE protection tier: "system" | "backup" | "user-data". The UI
	// is driven from it — system/backup get a lock badge and NO destructive controls; user-data is
	// customer-manageable (eject/wipe with type-to-confirm).
	Role         string  `json:"role"`
	DataBearing  bool    `json:"data_bearing"`
	DataReason   string  `json:"data_reason"`
	TotalBytes   int64   `json:"total_bytes"`
	UsedBytes    int64   `json:"used_bytes"`
	UsedFraction float64 `json:"used_fraction"`
	// DurableID is the target's stable identity (e.g. "uuid:<fs-uuid>" for usb/local-dir). The
	// fs UUID (strip the "uuid:" prefix) is the key the controller passes to AssignDisk — it's the
	// only way the de-privileged controller learns a mount key it cannot read off the device itself.
	DurableID string `json:"durable_id"`
}

// FSUUID returns the raw filesystem UUID from a "uuid:<…>" DurableID, or "" if this disk's identity
// is not a filesystem UUID (network/lvm targets — not assignable as a host mount).
func (d DiskInfo) FSUUID() string {
	if rest, ok := strings.CutPrefix(d.DurableID, "uuid:"); ok {
		return rest
	}
	return ""
}

// DisksResponse mirrors GET /disks.
type DisksResponse struct {
	VMID  int        `json:"vmid"`
	Disks []DiskInfo `json:"disks"`
}

// FormatResult mirrors POST /disks/format (the success/refusal payload).
type FormatResult struct {
	VMID        int    `json:"vmid"`
	Device      string `json:"device"`
	Formatted   bool   `json:"formatted"`
	DataBearing bool   `json:"data_bearing"`
	Reason      string `json:"reason"`
	// Role is the agent's tier for this device (system | backup | user-data).
	Role string `json:"role,omitempty"`
	// NeedsConfirmation is set on a USER-DATA data-bearing refusal: re-submit with confirmed=true +
	// DurableID after the type-to-confirm UI (NOT an operator signature).
	NeedsConfirmation bool   `json:"needs_confirmation,omitempty"`
	DurableID         string `json:"durable_id,omitempty"`
	// PendingOp is set on a SYSTEM/BACKUP data-bearing refusal — the operator-signature op.
	PendingOp *PendingOp `json:"pending_op,omitempty"`
}

// PendingOp mirrors the agent's bound destructive intent on a data-bearing refusal. The controller
// surfaces the exact `felhom-opsign` command from it — it CANNOT complete a destructive format itself.
type PendingOp struct {
	Op        string `json:"op"`         // e.g. "storage_wipe"
	HostScope string `json:"host_scope"` // the agent's host id (anti-retarget)
	DurableID string `json:"durable_id"` // byid:…|byuuid:… — the device's stable identity
	FSType    string `json:"fstype"`     // the filesystem to mkfs after the wipe
}

// OpsignCommand returns the literal command the operator must run offline to authorize the wipe.
func (p PendingOp) OpsignCommand() string {
	return fmt.Sprintf("felhom-opsign -op %s -host %s -durable-id %s", p.Op, p.HostScope, p.DurableID)
}

// ErrFormatRefused is returned by FormatDisk when the agent refuses a data-bearing format on a
// SYSTEM/BACKUP device (operator signature required). The UI surfaces the pending opsign command.
var ErrFormatRefused = fmt.Errorf("agentapi: format refused — system/backup device (operator authorization required)")

// ErrNeedsConfirmation is returned by FormatDisk when the agent refuses a data-bearing format on a
// USER-DATA device pending the CUSTOMER's informed-confirmation (bound to FormatResult.DurableID).
// The UI surfaces the type-to-confirm flow, then re-submits with confirmed=true + that durable id.
var ErrNeedsConfirmation = fmt.Errorf("agentapi: format needs customer confirmation — user-data device")

// Disks lists the host drives the agent manages, with a data-bearing flag per drive.
func (c *Client) Disks(ctx context.Context) (DisksResponse, error) {
	var out DisksResponse
	body, err := c.get(ctx, "/disks")
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode /disks: %w", err)
	}
	return out, nil
}

// AssignDisk attaches a drive (by fs-UUID) as a host mount (benign, self-serve).
func (c *Client) AssignDisk(ctx context.Context, uuid, where, fstype, options string) error {
	_, err := c.post(ctx, "/disks/assign", map[string]string{
		"uuid": uuid, "where": where, "fstype": fstype, "options": options,
	})
	return err
}

// EjectResult mirrors POST /disks/eject (the dependent-guest warning).
type EjectResult struct {
	VMID            int    `json:"vmid"`
	Ejected         string `json:"ejected"`
	DependentGuests []int  `json:"dependent_guests"`
}

// EjectDisk safe-unmounts a host mount (data preserved) and returns the dependent guests.
func (c *Client) EjectDisk(ctx context.Context, where string) (EjectResult, error) {
	var out EjectResult
	body, err := c.post(ctx, "/disks/eject", map[string]string{"where": where})
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode /disks/eject: %w", err)
	}
	return out, nil
}

// FormatDisk asks the agent to format a device. The AGENT inspects the device and tiers it by ROLE
// (its own classification, never the controller's claim):
//   - blank device → formatted.
//   - user-data, data-bearing, NOT confirmed → ErrNeedsConfirmation (out.DurableID = the id to confirm).
//   - user-data, data-bearing, confirmed + matching durable id → formatted.
//   - system/backup, data-bearing → ErrFormatRefused (out.PendingOp = the operator opsign command).
//
// confirmed + durableID authorize a user-data wipe (the durable id the agent gave on the prior
// ErrNeedsConfirmation); they are inert for system/backup.
func (c *Client) FormatDisk(ctx context.Context, device, fstype string, confirmed bool, durableID string) (FormatResult, error) {
	var out FormatResult
	// Status-aware POST: the agent returns the FULL FormatResponse (incl. pending_op / durable_id)
	// even on the 403 refusal, so we must read the body on non-2xx rather than discarding it.
	data, status, err := c.postWithStatus(ctx, "/disks/format", map[string]any{
		"device": device, "fstype": fstype, "confirmed": confirmed, "durable_id": durableID,
	})
	if err != nil {
		return out, err
	}
	// data is the envelope's {data:…} payload (present on both success and the 403 refusal).
	if len(data) > 0 {
		_ = json.Unmarshal(data, &out) // best-effort; fields default on a missing/partial body
	}
	if out.Formatted {
		return out, nil
	}
	if out.NeedsConfirmation {
		out.DataBearing = true
		return out, ErrNeedsConfirmation // user-data: surface the type-to-confirm flow
	}
	if status == http.StatusForbidden || (out.DataBearing && !out.Formatted) {
		out.DataBearing = true
		return out, ErrFormatRefused // system/backup: surface the opsign command
	}
	return out, nil
}

// postWithStatus issues an authenticated JSON POST and returns the envelope's data payload + the HTTP
// status, even on a non-2xx (so callers like FormatDisk can read a 403 refusal body). A transport or
// envelope-parse failure is still an error; an `ok:false` business refusal is NOT (the data carries it).
func (c *Client) postWithStatus(ctx context.Context, path string, body any) (json.RawMessage, int, error) {
	buf, err := json.Marshal(body)
	if err != nil {
		return nil, 0, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+path, bytes.NewReader(buf))
	if err != nil {
		return nil, 0, err
	}
	req.Header.Set("Authorization", "Bearer "+c.token)
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.hc.Do(req)
	if err != nil {
		return nil, 0, fmt.Errorf("agentapi: POST %s: %w", path, err)
	}
	defer resp.Body.Close()
	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	var env apiResponse
	if err := json.Unmarshal(raw, &env); err != nil {
		return nil, resp.StatusCode, fmt.Errorf("agentapi: POST %s: HTTP %d, bad envelope: %w", path, resp.StatusCode, err)
	}
	return env.Data, resp.StatusCode, nil
}

// ---- slice 9: host metrics (the customer host-health view) -------------------------------

// HostMetrics mirrors the agent's GET /host/metrics `host` block (shared HostMetrics wire shape).
// CPUTempC is a pointer so a host with no temp sensor is null ("n/a"), distinct from a real 0.
type HostMetrics struct {
	Node             string   `json:"node"`
	CPUPercent       float64  `json:"cpu_percent"` // 0–100
	MemoryTotalBytes int64    `json:"memory_total_bytes"`
	MemoryUsedBytes  int64    `json:"memory_used_bytes"`
	MemoryPercent    float64  `json:"memory_percent"`
	DiskTotalBytes   int64    `json:"disk_total_bytes"` // host root fs
	DiskUsedBytes    int64    `json:"disk_used_bytes"`
	DiskPercent      float64  `json:"disk_percent"`
	LoadAvg          []string `json:"loadavg"`
	UptimeSeconds    int64    `json:"uptime_seconds"`
	CPUTempC         *int     `json:"cpu_temp_c"` // °C or null ("n/a")
}

// ThinPoolFill mirrors the agent's lvmthin pool fill (a full thin-pool corrupts every guest on it).
type ThinPoolFill struct {
	DataUsedFraction     float64  `json:"data_used_fraction"`
	MetadataUsedFraction *float64 `json:"metadata_used_fraction"`
}

// SmartSummary mirrors the agent's per-disk SMART health (only the fields the UI renders). Pointers
// are null when the device type does not expose that attribute.
type SmartSummary struct {
	Health         string `json:"health"` // PASSED | FAILING | UNKNOWN
	TemperatureC   *int   `json:"temperature_c"`
	PercentageUsed *int   `json:"percentage_used"` // NVMe wear (%); null for SATA/USB
}

// StorageTarget mirrors the agent's GET /host/metrics storage_targets entry (the per-storage
// capacity + health the monitoring view renders). It is a SUBSET of the agent's wire shape — only
// the fields the UI reads; unknown JSON keys are ignored.
type StorageTarget struct {
	Name         string        `json:"name"`
	Type         string        `json:"type"`
	State        string        `json:"state"`
	Reachable    bool          `json:"reachable"`
	TotalBytes   int64         `json:"total_bytes"`
	UsedBytes    int64         `json:"used_bytes"`
	AvailBytes   int64         `json:"avail_bytes"`
	UsedFraction float64       `json:"used_fraction"`
	Content      string        `json:"content"`
	MountPath    string        `json:"mount_path"`
	ClassHint    string        `json:"class_hint"`
	ThinPool     *ThinPoolFill `json:"thin_pool,omitempty"`
	Smart        SmartSummary  `json:"smart"`
}

// HostMetricsResponse mirrors the agent's GET /host/metrics payload (host-wide health + per-storage
// capacity). Host-wide and token-authed (one-customer-per-host); a fresh collect, not a snapshot.
type HostMetricsResponse struct {
	VMID           int             `json:"vmid"`
	Host           HostMetrics     `json:"host"`
	StorageTargets []StorageTarget `json:"storage_targets"`
}

// HostMetrics calls GET /host/metrics and returns the host's live health + per-storage capacity.
func (c *Client) HostMetrics(ctx context.Context) (HostMetricsResponse, error) {
	var out HostMetricsResponse
	body, err := c.get(ctx, "/host/metrics")
	if err != nil {
		return out, err
	}
	if err := json.Unmarshal(body, &out); err != nil {
		return out, fmt.Errorf("agentapi: decode /host/metrics: %w", err)
	}
	return out, nil
}

// get issues an authenticated GET and unwraps the {ok,data,error} envelope.
func (c *Client) get(ctx context.Context, path string) (json.RawMessage, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+path, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Authorization", "Bearer "+c.token)
	resp, err := c.hc.Do(req)
	if err != nil {
		return nil, fmt.Errorf("agentapi: GET %s: %w", path, err)
	}
	defer resp.Body.Close()
	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("agentapi: GET %s: HTTP %d", path, resp.StatusCode)
	}
	var env apiResponse
	if err := json.Unmarshal(raw, &env); err != nil {
		return nil, fmt.Errorf("agentapi: GET %s: bad envelope: %w", path, err)
	}
	if !env.OK {
		return nil, fmt.Errorf("agentapi: GET %s: %s", path, env.Error)
	}
	return env.Data, nil
}

// post issues an authenticated JSON POST and unwraps the {ok,data,error} envelope. The agent
// returns 200 or 202 for accepted requests.
func (c *Client) post(ctx context.Context, path string, body any) (json.RawMessage, error) {
	buf, err := json.Marshal(body)
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+path, bytes.NewReader(buf))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Authorization", "Bearer "+c.token)
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.hc.Do(req)
	if err != nil {
		return nil, fmt.Errorf("agentapi: POST %s: %w", path, err)
	}
	defer resp.Body.Close()
	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusAccepted {
		return nil, fmt.Errorf("agentapi: POST %s: HTTP %d", path, resp.StatusCode)
	}
	var env apiResponse
	if err := json.Unmarshal(raw, &env); err != nil {
		return nil, fmt.Errorf("agentapi: POST %s: bad envelope: %w", path, err)
	}
	if !env.OK {
		return nil, fmt.Errorf("agentapi: POST %s: %s", path, env.Error)
	}
	return env.Data, nil
}

// normalizeFingerprint lowercases and strips ':'/' ' separators, requiring a 64-hex SHA-256.
func normalizeFingerprint(fp string) (string, error) {
	s := strings.ToLower(strings.NewReplacer(":", "", " ", "", "\t", "").Replace(strings.TrimSpace(fp)))
	if len(s) != 64 {
		return "", fmt.Errorf("agentapi: fingerprint must be a SHA-256 (64 hex chars), got %d", len(s))
	}
	if _, err := hex.DecodeString(s); err != nil {
		return "", fmt.Errorf("agentapi: fingerprint is not valid hex: %w", err)
	}
	return s, nil
}