// Package compose implements the "compose" source: a docker-compose stack
// deployed as a single logical unit. Multiple service containers may
// result; each becomes one row in the containers index keyed by service
// name in Container.Role.
package compose

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/alexei/tinyforge/internal/stack"
	"github.com/alexei/tinyforge/internal/store"
	"github.com/alexei/tinyforge/internal/workload/plugin"
)

// Config is the per-workload source config blob. ComposeYAML is the
// authoritative spec — either inline (manual / paste-in flow) or fetched
// by a git trigger and stashed here on each deploy. ComposeProjectName
// is the `-p` arg passed to docker compose; defaults to a stable
// workload-derived value when blank.
type Config struct {
	ComposeYAML        string `json:"compose_yaml"`
	ComposeProjectName string `json:"compose_project_name"`
}

type source struct{}

// composeRunner is the slice of stack.Compose this plugin actually
// drives. Defined locally per the "interfaces where they are used"
// idiom so the plugin can be unit-tested without a real docker compose
// binary. `*stack.Compose` satisfies it implicitly.
type composeRunner interface {
	Up(ctx context.Context, projectName, yamlPath string) (string, error)
	Down(ctx context.Context, projectName string, removeVolumes bool) (string, error)
	Ps(ctx context.Context, projectName, yamlPath string) ([]stack.Service, error)
}

// newComposeRunner returns the runner the plugin should call. Tests
// swap this var with a fake; production code never touches it. The
// indirection costs one function-pointer dereference per Deploy /
// Teardown / Reconcile call — negligible against the docker compose
// exec it gates.
var newComposeRunner = func() composeRunner { return stack.NewCompose("") }

func init() { plugin.RegisterSource(&source{}) }

func (*source) Kind() string { return "compose" }

func (*source) SchemaSample() any {
	return Config{
		ComposeYAML: "services:\n  web:\n    image: nginx:alpine\n    ports:\n      - \"80\"\n",
	}
}

func (*source) Validate(cfg json.RawMessage) error {
	var c Config
	if len(cfg) == 0 {
		return fmt.Errorf("compose source: config is required")
	}
	if err := json.Unmarshal(cfg, &c); err != nil {
		return fmt.Errorf("compose source: invalid json: %w", err)
	}
	if strings.TrimSpace(c.ComposeYAML) == "" {
		return fmt.Errorf("compose source: compose_yaml is required")
	}
	spec, err := stack.Parse(c.ComposeYAML)
	if err != nil {
		return fmt.Errorf("compose source: parse yaml: %w", err)
	}
	if err := stack.Validate(spec); err != nil {
		return fmt.Errorf("compose source: validate yaml: %w", err)
	}
	return nil
}

// Deploy writes the compose YAML to a stable per-workload path, runs
// `docker compose -p <project> up -d`, then syncs one Container row per
// service. The workload ID is the natural compose project name unless
// the user supplied one explicitly.
func (*source) Deploy(ctx context.Context, deps plugin.Deps, w plugin.Workload, intent plugin.DeploymentIntent) error {
	cfg, err := plugin.SourceConfigOf[Config](w)
	if err != nil {
		return fmt.Errorf("compose source: decode config: %w", err)
	}
	if strings.TrimSpace(cfg.ComposeYAML) == "" {
		return fmt.Errorf("compose source: workload %s has empty compose_yaml", w.ID)
	}

	projectName := composeProjectName(cfg.ComposeProjectName, w)
	yamlPath, err := writeYAML(w.ID, cfg.ComposeYAML)
	if err != nil {
		return fmt.Errorf("compose source: write yaml: %w", err)
	}

	compose := newComposeRunner()
	out, err := compose.Up(ctx, projectName, yamlPath)
	if err != nil {
		return fmt.Errorf("compose source: docker compose up: %w (output: %s)", err, truncate(out, 1024))
	}

	if err := syncContainers(ctx, deps, compose, w, projectName, yamlPath); err != nil {
		// `up` succeeded but we could not enumerate the resulting
		// containers — surface the failure so the UI does not show an
		// empty containers index for a running stack.
		return fmt.Errorf("compose source: sync container rows: %w", err)
	}
	return nil
}

// Teardown runs `docker compose down --remove-orphans -v` and drops the
// container rows. Idempotent: missing compose project is treated as
// already-down. Volume removal is intentional — workload teardown is
// destructive by design (matches `DeleteStack(removeVolumes=true)`).
func (*source) Teardown(ctx context.Context, deps plugin.Deps, w plugin.Workload) error {
	cfg, _ := plugin.SourceConfigOf[Config](w)
	projectName := composeProjectName(cfg.ComposeProjectName, w)

	compose := newComposeRunner()
	if _, err := compose.Down(ctx, projectName, true); err != nil {
		// Log but proceed — the DB rows must not be orphaned.
		slog.Warn("compose source: docker compose down", "workload", w.ID, "error", err)
	}

	// Best-effort: remove the YAML scratch dir.
	_ = os.RemoveAll(workloadDir(w.ID))

	rows, err := deps.Store.ListContainersByWorkload(w.ID)
	if err != nil {
		return fmt.Errorf("compose source: list containers: %w", err)
	}
	for _, c := range rows {
		if err := deps.Store.DeleteContainer(c.ID); err != nil && !errors.Is(err, store.ErrNotFound) {
			slog.Warn("compose source: delete container row", "id", c.ID, "error", err)
		}
	}
	return nil
}

// Reconcile refreshes the containers index from `docker compose ps`. If
// the compose project is unknown to Docker, container rows are marked
// missing so the UI flags them. The reconciler hits this on every tick
// per workload, so the YAML is only rewritten when its content has
// actually changed.
func (*source) Reconcile(ctx context.Context, deps plugin.Deps, w plugin.Workload) error {
	cfg, err := plugin.SourceConfigOf[Config](w)
	if err != nil {
		return fmt.Errorf("compose source: decode config: %w", err)
	}
	projectName := composeProjectName(cfg.ComposeProjectName, w)
	yamlPath, _ := writeYAMLIfChanged(w.ID, cfg.ComposeYAML)

	compose := newComposeRunner()
	services, err := compose.Ps(ctx, projectName, yamlPath)
	if err != nil {
		// Likely no compose project running for this workload. Mark
		// existing rows missing so the UI surfaces it.
		rows, _ := deps.Store.ListContainersByWorkload(w.ID)
		for _, c := range rows {
			_ = deps.Store.UpdateContainerState(c.ID, "missing")
		}
		return nil
	}
	for _, svc := range services {
		state := svc.State
		if state == "" {
			state = svc.Status
		}
		upsertServiceRow(deps, w, svc, state)
	}
	return nil
}

// syncContainers shares its body with Reconcile minus the missing-row
// fallback — Deploy expects compose ps to succeed since `up` just ran.
func syncContainers(ctx context.Context, deps plugin.Deps, compose composeRunner, w plugin.Workload, projectName, yamlPath string) error {
	services, err := compose.Ps(ctx, projectName, yamlPath)
	if err != nil {
		return fmt.Errorf("compose ps: %w", err)
	}
	for _, svc := range services {
		state := svc.State
		if state == "" {
			state = svc.Status
		}
		upsertServiceRow(deps, w, svc, state)
	}
	return nil
}

func upsertServiceRow(deps plugin.Deps, w plugin.Workload, svc stack.Service, state string) {
	role := svc.Service
	if role == "" {
		role = svc.Name
	}
	if err := deps.Store.UpsertContainer(store.Container{
		ID:           w.ID + ":" + role,
		WorkloadID:   w.ID,
		WorkloadKind: "compose",
		Role:         role,
		ContainerID:  "", // reconciler fills via `docker ps` label join
		Host:         "local",
		State:        state,
		LastSeenAt:   store.Now(),
	}); err != nil {
		slog.Warn("compose source: upsert container row", "workload", w.ID, "service", role, "error", err)
	}
}

// composeProjectName returns the `-p` argument for docker compose. We
// always derive a stable name from the workload (sanitized + truncated
// ID) when the user did not set ComposeProjectName, so re-deploys of the
// same workload reuse the same project.
var projectNameSanitizer = regexp.MustCompile(`[^a-z0-9_-]`)

func composeProjectName(explicit string, w plugin.Workload) string {
	if explicit != "" {
		// Apply the same sanitizer to operator-supplied names so a value
		// like "--foo" cannot reach the docker CLI and be re-parsed as a
		// flag. Reuses the canonical lower+[^a-z0-9_-]→"-" + trim path.
		san := strings.ToLower(explicit)
		san = projectNameSanitizer.ReplaceAllString(san, "-")
		san = strings.Trim(san, "-")
		if san != "" {
			return san
		}
		// Fall through to the derived name if sanitization stripped
		// everything (operator passed e.g. "---" — degenerate input).
	}
	name := strings.ToLower(w.Name)
	name = projectNameSanitizer.ReplaceAllString(name, "-")
	name = strings.Trim(name, "-")
	if name == "" {
		name = "wkl"
	}
	idShort := w.ID
	if len(idShort) > 8 {
		idShort = idShort[:8]
	}
	return fmt.Sprintf("tf-%s-%s", name, idShort)
}

// workloadDir is the per-workload scratch directory for compose YAML.
func workloadDir(workloadID string) string {
	return filepath.Join(os.TempDir(), "tinyforge-compose", workloadID)
}

// writeYAML writes the current compose YAML to a stable path under the
// workload's scratch dir. Returns the path. Each deploy overwrites the
// file — there are no revisions at the source level (the workload row is
// the single source of truth; git or registry triggers update SourceConfig).
//
// Permissions are owner-only (0o700 / 0o600) because the YAML often
// contains environment-section secrets and the dir lives in shared /tmp.
func writeYAML(workloadID, yamlText string) (string, error) {
	dir := workloadDir(workloadID)
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return "", err
	}
	path := filepath.Join(dir, "compose.yml")
	if err := os.WriteFile(path, []byte(yamlText), 0o600); err != nil {
		return "", err
	}
	return path, nil
}

// writeYAMLIfChanged is writeYAML minus the disk write when the existing
// file already matches yamlText. Used by Reconcile, which runs per
// workload per tick; redundant fsync churn was a measurable cost.
func writeYAMLIfChanged(workloadID, yamlText string) (string, error) {
	dir := workloadDir(workloadID)
	path := filepath.Join(dir, "compose.yml")
	if existing, err := os.ReadFile(path); err == nil && string(existing) == yamlText {
		return path, nil
	}
	return writeYAML(workloadID, yamlText)
}

func truncate(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "...(truncated)"
}