// Package doctor implements `orca doctor`, a small battery of self-checks
// for the orca installation. The cert, network, and db checks surface
// common configuration errors before they become runtime failures.
//
// REQ-032: `orca doctor` is a first-class subcommand in v0.2 P01.
// Per-phase subcommands:
//
//	orca doctor            — runs all checks, prints a summary
//	orca doctor cert       — CA, server cert, expiry, fingerprint pin
//	orca doctor network    — TCP reachability + mTLS handshake (stub in P01)
//	orca doctor db         — SQLite open + migration apply (stub in P01)
//
// Each check returns a Result of PASS, WARN, or FAIL with a free-form
// message. The aggregator prints one line per check.
package doctor

import (
	"context"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"net/http"
	"os"
	"sort"
	"strings"
	"time"

	"golang.org/x/crypto/ssh"

	"git.cloudinit.dev/coreci/orca/internal/certpaths"
	"git.cloudinit.dev/coreci/orca/internal/model"
	"git.cloudinit.dev/coreci/orca/internal/osdetect"
	"git.cloudinit.dev/coreci/orca/internal/proxmox"
	"git.cloudinit.dev/coreci/orca/internal/security"
	"git.cloudinit.dev/coreci/orca/internal/store"
	"git.cloudinit.dev/coreci/orca/internal/transport"
)

// Result is the outcome of a single check.
type Result string

const (
	ResultPass Result = "PASS"
	ResultWarn Result = "WARN"
	ResultFail Result = "FAIL"
)

// Check is a single self-check.
type Check struct {
	Name        string
	Description string
	Run         func(ctx context.Context) (Result, string)
}

// Report is the aggregated result of running all checks.
type Report struct {
	Time   time.Time
	Checks []CheckResult
}

// CheckResult is the outcome of one Check.
type CheckResult struct {
	Name    string
	Result  Result
	Message string
}

// All returns the full battery of checks.
func All() []Check {
	return []Check{
		CertCA(),
		CertServer(),
		CertExpiry(),
		CertFingerprint(),
		OS(),
		Network(),
		Proxmox(),
		DB(),
	}
}

// Run executes every check and returns a Report.
func Run(ctx context.Context) *Report {
	checks := All()
	results := make([]CheckResult, 0, len(checks))
	for _, c := range checks {
		r, msg := c.Run(ctx)
		results = append(results, CheckResult{
			Name:    c.Name,
			Result:  r,
			Message: msg,
		})
	}
	return &Report{Time: time.Now(), Checks: results}
}

// Print renders the Report.
func (r *Report) Print() string {
	out := fmt.Sprintf("orca doctor — %s\n\n", r.Time.UTC().Format(time.RFC3339))
	pass, warn, fail := 0, 0, 0
	sort.Slice(r.Checks, func(i, j int) bool { return r.Checks[i].Name < r.Checks[j].Name })
	for _, c := range r.Checks {
		out += fmt.Sprintf("%-20s %-5s  %s\n", c.Name, c.Result, c.Message)
		switch c.Result {
		case ResultPass:
			pass++
		case ResultWarn:
			warn++
		case ResultFail:
			fail++
		}
	}
	out += fmt.Sprintf("\n%d PASS, %d WARN, %d FAIL\n", pass, warn, fail)
	return out
}

// CertCA checks the on-disk CA exists with the right file modes (REQ-033).
func CertCA() Check {
	return Check{
		Name:        "cert.ca",
		Description: "CA at ~/.orca with mode 0600/0644 (REQ-033)",
		Run: func(_ context.Context) (Result, string) {
			dir := certpaths.Dir()
			if err := security.EnforceFileModes(dir); err != nil {
				return ResultFail, err.Error()
			}
			return ResultPass, fmt.Sprintf("CA at %s with mode 0644/0600", dir)
		},
	}
}

// CertServer checks the server cert is present and parseable.
func CertServer() Check {
	return Check{
		Name:        "cert.server",
		Description: "server.crt exists, signed by local CA",
		Run: func(_ context.Context) (Result, string) {
			certPath := certpaths.ServerCertPath()
			if _, err := os.Stat(certPath); err != nil {
				return ResultFail, fmt.Sprintf("server cert missing: %v", err)
			}
			fp, err := security.Fingerprint(certPath)
			if err != nil {
				return ResultFail, err.Error()
			}
			return ResultPass, fmt.Sprintf("server cert at %s, fp=%s", certPath, fp[:16]+"...")
		},
	}
}

// CertExpiry returns WARN if the server cert is within 30 days of expiry
// (REQ-034). Otherwise PASS.
func CertExpiry() Check {
	return Check{
		Name:        "cert.expiry",
		Description: "server cert validity window (> 30d = PASS, ≤ 30d = WARN)",
		Run: func(_ context.Context) (Result, string) {
			cert, err := loadCert(certpaths.ServerCertPath())
			if err != nil {
				return ResultFail, err.Error()
			}
			remaining := time.Until(cert.NotAfter)
			days := int(remaining.Hours() / 24)
			if days < 0 {
				return ResultFail, fmt.Sprintf("server cert EXPIRED %dd ago", -days)
			}
			if days <= 30 {
				return ResultWarn, fmt.Sprintf("server cert expires in %dd — run `orca cert renew`", days)
			}
			return ResultPass, fmt.Sprintf("server cert valid for %dd more", days)
		},
	}
}

// CertFingerprint prints the CA fingerprint so the operator can copy
// it to peers. Always PASS (or FAIL if the cert is missing).
func CertFingerprint() Check {
	return Check{
		Name:        "cert.fingerprint",
		Description: "CA fingerprint (for cross-node pinning)",
		Run: func(_ context.Context) (Result, string) {
			fp, err := security.Fingerprint(certpaths.CACertPath())
			if err != nil {
				return ResultFail, err.Error()
			}
			return ResultPass, fmt.Sprintf("CA fp=%s (use at `orca node join --ca-fingerprint`)", fp)
		},
	}
}

// DB checks SQLite integrity and migration version (REQ-032 completion).
func DB() Check {
	return Check{
		Name:        "db",
		Description: "SQLite integrity_check + migration version",
		Run: func(ctx context.Context) (Result, string) {
			path := certpaths.DBPath()
			db, err := store.Open(path)
			if err != nil {
				return ResultFail, fmt.Sprintf("open db: %v", err)
			}
			defer db.Close()

			var integrity string
			if err := db.QueryRowContext(ctx, "PRAGMA integrity_check").Scan(&integrity); err != nil {
				return ResultFail, fmt.Sprintf("integrity_check: %v", err)
			}
			if !strings.EqualFold(integrity, "ok") {
				return ResultFail, fmt.Sprintf("integrity_check: %s", integrity)
			}

			version, err := store.MigrationVersion(ctx, db)
			if err != nil {
				return ResultFail, fmt.Sprintf("migration version: %v", err)
			}
			if version == "" {
				return ResultWarn, "integrity OK but no migrations applied (fresh db)"
			}
			return ResultPass, fmt.Sprintf("integrity OK, migrations up to %s", version)
		},
	}
}

// Network probes peer reachability via mTLS /healthz (REQ-032 completion).
// Peers are sourced from the persisted nodes table (not the in-memory
// PeerRegistry, which is empty at CLI time). Zero peers → WARN (single-node
// is legitimate). Any peer unreachable → FAIL (D-038).
func Network() Check {
	return Check{
		Name:        "network",
		Description: "peer reachability via mTLS /healthz probe",
		Run: func(ctx context.Context) (Result, string) {
			caPath := certpaths.CACertPath()
			certPath := certpaths.ServerCertPath()
			keyPath := certpaths.ServerKeyPath()

			// Check that cert files exist before attempting probes.
			if _, err := os.Stat(caPath); err != nil {
				return ResultFail, fmt.Sprintf("CA cert missing: %v (run `orca cert init`)", err)
			}

			path := certpaths.DBPath()
			db, err := store.Open(path)
			if err != nil {
				return ResultFail, fmt.Sprintf("open db: %v", err)
			}
			defer db.Close()

			nodes, err := store.NewNodeRepo(db).List(ctx)
			if err != nil {
				return ResultFail, fmt.Sprintf("list nodes: %v", err)
			}

			live := make([]*model.Node, 0, len(nodes))
			for _, n := range nodes {
				if n.State != model.NodeStateLeft {
					live = append(live, n)
				}
			}

			if len(live) == 0 {
				return ResultWarn, "no peers registered (single-node?)"
			}

			var lines []string
			anyFail := false
			for _, n := range live {
				probeCtx, cancel := context.WithTimeout(ctx, 3*time.Second)
				err := probeHealthz(probeCtx, caPath, certPath, keyPath, n.Name, n.Address)
				cancel()
				if err != nil {
					anyFail = true
					lines = append(lines, fmt.Sprintf("  ✗ %s (%s): %v", n.Name, n.Address, err))
				} else {
					lines = append(lines, fmt.Sprintf("  ✓ %s (%s)", n.Name, n.Address))
				}
			}

			result := ResultPass
			if anyFail {
				result = ResultFail
			}
			return result, strings.Join(lines, "\n")
		},
	}
}

// probeHealthz opens an mTLS connection to the peer and GETs /healthz.
func probeHealthz(ctx context.Context, caPath, certPath, keyPath, serverName, addr string) error {
	client, err := transport.NewMTLSClient(caPath, serverName, certPath, keyPath)
	if err != nil {
		return fmt.Errorf("mTLS client: %w", err)
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://"+addr+"/healthz", nil)
	if err != nil {
		return fmt.Errorf("request: %w", err)
	}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("probe: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("healthz returned %d", resp.StatusCode)
	}
	return nil
}

// OS checks that the auto-detected OS matches the stored localhost
// node's os field (REQ-052). Drift (e.g., OS upgraded since init)
// returns WARN; match returns PASS; missing localhost node returns FAIL.
func OS() Check {
	return Check{
		Name:        "os",
		Description: "localhost OS detection vs stored node row",
		Run: func(ctx context.Context) (Result, string) {
			detected := osdetect.Detect()

			db, err := store.Open(certpaths.DBPath())
			if err != nil {
				return ResultFail, fmt.Sprintf("open db: %v", err)
			}
			defer db.Close()

			node, err := store.NewNodeRepo(db).GetByName(ctx, "localhost")
			if err == store.ErrNotFound {
				return ResultFail, "no localhost node registered — run `orca init`"
			}
			if err != nil {
				return ResultFail, fmt.Sprintf("lookup localhost node: %v", err)
			}
			if node.OS == "" {
				return ResultWarn, fmt.Sprintf("localhost node has no os field (pre-0006 row?); detected=%s — re-run `orca init` to refresh", detected)
			}
			if node.OS != detected {
				return ResultWarn, fmt.Sprintf("OS drift: init=%s, now=%s — re-run `orca init` to refresh", node.OS, detected)
			}
			return ResultPass, fmt.Sprintf("localhost os=%s (matches /etc/os-release)", detected)
		},
	}
}

// Proxmox probes each kind=proxmox node via SSH with `pveversion`
// (REQ-052). Clones the Network() pattern: list nodes, filter by kind,
// 3s timeout per peer, PASS/WARN/FAIL per node. Zero proxmox nodes
// returns WARN (single-node cluster is legitimate).
func Proxmox() Check {
	return Check{
		Name:        "proxmox",
		Description: "proxmox node reachability via SSH pveversion probe",
		Run: func(ctx context.Context) (Result, string) {
			db, err := store.Open(certpaths.DBPath())
			if err != nil {
				return ResultFail, fmt.Sprintf("open db: %v", err)
			}
			defer db.Close()

			nodes, err := store.NewNodeRepo(db).List(ctx)
			if err != nil {
				return ResultFail, fmt.Sprintf("list nodes: %v", err)
			}

			proxmoxNodes := make([]*model.Node, 0, len(nodes))
			for _, n := range nodes {
				if n.Kind == string(model.NodeKindProxmox) && n.State != model.NodeStateLeft {
					proxmoxNodes = append(proxmoxNodes, n)
				}
			}

			if len(proxmoxNodes) == 0 {
				return ResultWarn, "no proxmox nodes registered (single-node?)"
			}

			var lines []string
			anyFail := false
			for _, n := range proxmoxNodes {
				probeCtx, cancel := context.WithTimeout(ctx, 3*time.Second)
				err := probeProxmoxPVEVersion(probeCtx, n.Name)
				cancel()
				if err != nil {
					anyFail = true
					lines = append(lines, fmt.Sprintf("  ✗ %s: %v", n.Name, err))
				} else {
					lines = append(lines, fmt.Sprintf("  ✓ %s", n.Name))
				}
			}

			result := ResultPass
			if anyFail {
				result = ResultFail
			}
			return result, strings.Join(lines, "\n")
		},
	}
}

// probeProxmoxPVEVersion SSHes into the proxmox host and runs
// `pveversion` to verify reachability + PVE installation. Uses the
// orca SSH key for auth (deployed during `orca node join --type proxmox`)
// and the known_hosts TOFU store for host-key verification (D-035).
func probeProxmoxPVEVersion(ctx context.Context, host string) error {
	// Load the orca SSH key for public-key auth.
	keyPEM, err := os.ReadFile(certpaths.SSHKeyPath())
	if err != nil {
		return fmt.Errorf("read SSH key: %w (run `orca node join --type proxmox` first)", err)
	}
	signer, err := ssh.ParsePrivateKey(keyPEM)
	if err != nil {
		return fmt.Errorf("parse SSH key: %w", err)
	}

	// Extract host from the node address (orca stores host:8443;
	// SSH needs host:22). We dial the SSH port, not the orca daemon port.
	sshHost := host
	if strings.Contains(host, ":") {
		sshHost = strings.SplitN(host, ":", 2)[0]
	}
	sshAddr := sshHost + ":22"

	// Use the shared TOFU capture-fix wrapper (T02.9 — GRILL condition
	// #2: doctor parity with bootstrap). Without this, a first-connect
	// proxmox node (entry missing from known_hosts) fails the doctor
	// probe even though it joined fine — the v0.6 ship-defect.
	hostKeyCallback, err := proxmox.TOFUHostKeyCallback(sshAddr, nil)
	if err != nil {
		return fmt.Errorf("known_hosts: %w", err)
	}

	config := &ssh.ClientConfig{
		User:            "orca",
		Auth:            []ssh.AuthMethod{ssh.PublicKeys(signer)},
		HostKeyCallback: hostKeyCallback,
		Timeout:         3 * time.Second,
	}

	dialer := &netDialer{}
	conn, err := dialer.DialContext(ctx, "tcp", sshAddr, config)
	if err != nil {
		return fmt.Errorf("ssh dial: %w", err)
	}
	defer conn.Close()

	session, err := conn.NewSession()
	if err != nil {
		return fmt.Errorf("new session: %w", err)
	}
	defer session.Close()

	out, err := session.CombinedOutput("pveversion")
	if err != nil {
		return fmt.Errorf("pveversion: %w (output: %s)", err, strings.TrimSpace(string(out)))
	}
	return nil
}

// netDialer wraps ssh.Dial with context support. The ssh package's
// Dial doesn't accept a context directly, so we use a dialer that
// respects ctx cancellation via a goroutine + channel.
type netDialer struct{}

func (d *netDialer) DialContext(ctx context.Context, network, addr string, config *ssh.ClientConfig) (*ssh.Client, error) {
	type result struct {
		client *ssh.Client
		err    error
	}
	ch := make(chan result, 1)
	go func() {
		client, err := ssh.Dial(network, addr, config)
		ch <- result{client, err}
	}()
	select {
	case <-ctx.Done():
		// Best-effort: if the dial succeeds after ctx cancellation,
		// the goroutine will close the client. We return the ctx error.
		go func() {
			if r := <-ch; r.client != nil {
				_ = r.client.Close()
			}
		}()
		return nil, ctx.Err()
	case r := <-ch:
		return r.client, r.err
	}
}

// loadCert reads a PEM cert from path and parses the first CERTIFICATE
// block.
func loadCert(path string) (*x509.Certificate, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read %s: %w", path, err)
	}
	block, _ := pem.Decode(data)
	if block == nil {
		return nil, fmt.Errorf("no PEM block in %s", path)
	}
	if block.Type != "CERTIFICATE" {
		return nil, fmt.Errorf("PEM type %q in %s, want CERTIFICATE", block.Type, path)
	}
	return x509.ParseCertificate(block.Bytes)
}