// Package bootstrap implements first-run bootstrap.json ingestion (slice 8A → v0.40.0 onboarding,
// doc 03 §6, config-contract decision (c)/(d)). The host agent's provisioning back-half writes a
// stable bootstrap.json into a read-only config mount carrying ONLY the customer id, the hub URL, a
// per-customer RETRIEVAL PASSPHRASE, and the per-guest local-API handle. On first run the controller
// uses the passphrase to PULL its full controller.yaml from the hub (which mints the customer-scoped
// hub api_key + identity + assets + backup + CF config), MERGES in the per-guest local_api block (the
// only thing the hub yaml lacks, because the hub must not know per-guest Proxmox internals), writes
// it, and comes up CONFIGURED — skipping the setup wizard.
//
// This replaces the old "seed a configured yaml from the agent's HOST key" path, which made the
// controller's hub reports 401 (the hub's /report needs the customer-scoped key, not the host key).
package bootstrap

import (
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/config"
	"gopkg.in/yaml.v3"
)

// DefaultMountPath is where the agent attaches the read-only config mount (spike S2). Override
// with FELHOM_BOOTSTRAP_PATH for tests / non-standard layouts.
const DefaultMountPath = "/etc/felhom-bootstrap/bootstrap.json"

// SchemaV2 is the stable contract version the agent emits and the controller ingests. v2 changed the
// contract's MEANING (the controller pulls its config from the hub rather than seeding it from the
// agent's host key) and its field set, so it is a clean version bump with no v1 back-compat
// (pre-launch; zero v1 guests deployed). A non-v2 schema is rejected → setup mode.
const SchemaV2 = "felhom.bootstrap/v2"

// ErrPullTransient marks a pull failure as retryable (a boot-time network race reaching the hub).
// The wiring (main.go) wraps report.ErrHubUnreachable with this; permanent failures (auth /
// not-found) are NOT wrapped, so MaybeIngest fails fast on them. Keeping this sentinel here (rather
// than importing the heavy internal/report package) keeps bootstrap decoupled — decision (b).
var ErrPullTransient = errors.New("bootstrap: transient pull failure")

// pullRetryDelays is the backoff between transient pull retries (one initial attempt + one retry per
// entry → 4 attempts total on persistent transient failure). Overridable in tests for speed.
var pullRetryDelays = []time.Duration{2 * time.Second, 4 * time.Second, 8 * time.Second}

// PullFunc fetches a generated controller.yaml from the hub for a customer, authenticated by the
// retrieval passphrase. Injected (decision (b)) so MaybeIngest never imports internal/report; the
// production wiring passes report.PullConfig. A transient (retryable) failure must be
// errors.Is(err, ErrPullTransient); any other error is treated as permanent (no retry).
type PullFunc func(hubURL, customerID, retrievalPassword string) (string, error)

// Bootstrap is the stable agent→controller config contract (JSON, schema v2). It carries ONLY what
// the controller needs to PULL its config (customer id + hub url + retrieval passphrase) and reach
// the agent's local API (endpoint/fingerprint/token). It is deliberately a SEPARATE shape from
// controller.yaml: the agent never needs to know the controller's full config schema, and never
// holds the customer-scoped hub key or CF tokens (those come from the hub pull).
type Bootstrap struct {
	Schema   string            `json:"schema"`
	Customer BootstrapCustomer `json:"customer"` // only id (the pull target); the hub provides name/domain/email
	Hub      BootstrapHub      `json:"hub"`
	LocalAPI BootstrapLocalAPI `json:"local_api"`
}

type BootstrapCustomer struct {
	ID string `json:"id"`
}

type BootstrapHub struct {
	URL               string `json:"url"`
	RetrievalPassword string `json:"retrieval_password"` // SECRET — pulls the full config (incl. the customer key)
}

type BootstrapLocalAPI struct {
	Endpoint    string `json:"endpoint"`    // host bridge IP:port
	Fingerprint string `json:"fingerprint"` // agent leaf-cert SHA-256 (hex) to pin
	Token       string `json:"token"`       // per-guest bearer; SECRET
}

// Path returns the bootstrap mount path (env override → default).
func Path() string {
	if p := strings.TrimSpace(os.Getenv("FELHOM_BOOTSTRAP_PATH")); p != "" {
		return p
	}
	return DefaultMountPath
}

// MaybeIngest, on an unconfigured controller, pulls the full controller.yaml from the hub (using the
// bootstrap's retrieval passphrase), merges in the per-guest local_api block, writes controller.yaml,
// and returns the reloaded config. Returns the config the caller should use.
//
// Contract:
//   - Idempotent: if cfg is already configured (customer.id set), the existing controller.yaml is
//     NEVER clobbered and the hub is NEVER pulled — returns cfg unchanged.
//   - Fail-safe: an absent/malformed bootstrap, a non-v2 schema, a missing required field, or a hub
//     pull that ultimately fails leaves cfg unchanged (the caller proceeds to setup mode). It logs
//     and NEVER crashes — a hub outage at first boot must not brick the guest.
//   - On success: writes controller.yaml (0600, atomic), reloads it, and returns the reloaded cfg.
func MaybeIngest(configPath string, cfg *config.Config, logger *log.Logger, pull PullFunc) *config.Config {
	if cfg != nil && cfg.Customer.ID != "" {
		return cfg // already configured — do not clobber, do not pull (idempotent)
	}
	bpath := Path()
	data, err := os.ReadFile(bpath)
	if err != nil {
		if !os.IsNotExist(err) {
			logger.Printf("[WARN] bootstrap: cannot read %s: %v — staying in setup", bpath, err)
		}
		return cfg // no bootstrap → normal setup
	}

	var b Bootstrap
	if err := json.Unmarshal(data, &b); err != nil {
		logger.Printf("[WARN] bootstrap: %s is not valid JSON: %v — staying in setup", bpath, err)
		return cfg
	}
	if b.Schema != SchemaV2 {
		logger.Printf("[WARN] bootstrap: unsupported schema %q (want %q) — staying in setup", b.Schema, SchemaV2)
		return cfg
	}
	if b.Customer.ID == "" || b.Hub.URL == "" || b.Hub.RetrievalPassword == "" {
		logger.Printf("[WARN] bootstrap: %s missing customer.id / hub.url / hub.retrieval_password — staying in setup", bpath)
		return cfg
	}
	if b.LocalAPI.Endpoint == "" || b.LocalAPI.Fingerprint == "" || b.LocalAPI.Token == "" {
		logger.Printf("[WARN] bootstrap: %s missing local_api.{endpoint,fingerprint,token} — staying in setup", bpath)
		return cfg
	}
	if pull == nil {
		logger.Printf("[WARN] bootstrap: no pull function wired — staying in setup")
		return cfg
	}

	// --- Pull the full controller.yaml from the hub, with bounded retry on transient errors only. ---
	pulled, err := pullWithRetry(pull, b.Hub.URL, b.Customer.ID, b.Hub.RetrievalPassword, logger)
	if err != nil {
		logger.Printf("[WARN] bootstrap: hub config pull failed for customer %s from %s: %v — staying in setup (manual setup wizard remains the fallback)",
			b.Customer.ID, b.Hub.URL, err)
		return cfg
	}

	// --- Merge the per-guest local_api block into the hub yaml at the MAP level (decision (c)) so
	//     every field the hub emits is preserved (forward-compat with hub template changes). ---
	merged, err := mergeLocalAPI(pulled, b.LocalAPI)
	if err != nil {
		logger.Printf("[WARN] bootstrap: merging local_api into pulled config failed: %v — staying in setup", err)
		return cfg
	}
	if err := writeFileAtomic(configPath, merged); err != nil {
		logger.Printf("[WARN] bootstrap: could not write %s: %v — staying in setup", configPath, err)
		return cfg
	}
	reloaded, err := config.LoadPermissive(configPath)
	if err != nil {
		logger.Printf("[WARN] bootstrap: wrote %s but reload failed: %v — staying in setup", configPath, err)
		return cfg
	}
	logger.Printf("[INFO] bootstrap: pulled config from %s for %s, merged local_api (%s) — coming up configured",
		b.Hub.URL, b.Customer.ID, b.LocalAPI.Endpoint)
	return reloaded
}

// pullWithRetry calls pull once, then retries on transient (ErrPullTransient) failures only, with
// the pullRetryDelays backoff. Permanent failures (anything not ErrPullTransient) fail fast.
func pullWithRetry(pull PullFunc, hubURL, customerID, password string, logger *log.Logger) (string, error) {
	var lastErr error
	for attempt := 0; ; attempt++ {
		yaml, err := pull(hubURL, customerID, password)
		if err == nil {
			return yaml, nil
		}
		lastErr = err
		if !errors.Is(err, ErrPullTransient) {
			return "", err // permanent (auth/not-found/other) — no retry
		}
		if attempt >= len(pullRetryDelays) {
			break // exhausted retries
		}
		delay := pullRetryDelays[attempt]
		logger.Printf("[INFO] bootstrap: hub unreachable (attempt %d), retrying in %s …", attempt+1, delay)
		time.Sleep(delay)
	}
	return "", lastErr
}

// mergeLocalAPI parses the pulled controller.yaml as a generic map, sets the local_api block from the
// bootstrap (overwriting any hub-emitted placeholder), and re-marshals. local_api.enabled is NOT set
// — it defaults on once endpoint is present (config.LocalAPIConfig).
func mergeLocalAPI(pulledYAML string, la BootstrapLocalAPI) ([]byte, error) {
	m := map[string]any{}
	if err := yaml.Unmarshal([]byte(pulledYAML), &m); err != nil {
		return nil, fmt.Errorf("parse pulled yaml: %w", err)
	}
	m["local_api"] = map[string]any{
		"endpoint":    la.Endpoint,
		"fingerprint": la.Fingerprint,
		"token":       la.Token,
	}
	out, err := yaml.Marshal(m)
	if err != nil {
		return nil, fmt.Errorf("marshal merged yaml: %w", err)
	}
	return out, nil
}

// writeFileAtomic writes b to path atomically (tmp + rename), 0600 (it carries the local-api token +
// the customer hub key).
func writeFileAtomic(path string, b []byte) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return fmt.Errorf("config dir: %w", err)
	}
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, b, 0o600); err != nil {
		return err
	}
	return os.Rename(tmp, path)
}