// Package config loads repospawner runtime configuration from the environment.
package config

import (
	"fmt"
	"os"
	"strings"
)

// Config is the fully-resolved repospawner configuration. The same struct is
// loaded by the server and by the job subcommands, which run from the same
// image with the same environment.
type Config struct {
	// Listen is the HTTP listen address, e.g. ":8080".
	Listen string
	// Namespace is where request Jobs are created and looked up.
	Namespace string
	// Image is repospawner's own image reference; Jobs run it with a
	// different argv, so the deployment must pass its own tag through.
	Image string
	// JobServiceAccount is the service account the request Jobs run as; it
	// carries the projected vault-audience token.
	JobServiceAccount string
	// GiteaURL is the forge base URL, e.g. https://git.unkin.net.
	GiteaURL string
	// TFGitRepo is the "owner/name" of the terraform-git repository whose
	// config tree owns repository definitions.
	TFGitRepo string
	// VaultAddr, VaultK8sMount and VaultK8sRole drive the native kubernetes
	// auth login used to mint short-lived Gitea tokens.
	VaultAddr     string
	VaultK8sMount string
	VaultK8sRole  string
	// VaultSATokenPath is the projected service account token with the
	// "vault" audience.
	VaultSATokenPath string
	// GiteaCredsPath is the vault path of the dynamic Gitea credential.
	GiteaCredsPath string
	// WoodpeckerServer is the CI server base URL.
	WoodpeckerServer string
	// WoodpeckerTokenFile holds the Woodpecker API token. Absent means
	// Woodpecker enablement is unavailable, not fatal.
	WoodpeckerTokenFile string
	// WoodpeckerSecret is the Secret the enablement Job mounts to obtain
	// WoodpeckerTokenFile; the server reads the same file to decide whether
	// enablement is offered at all.
	WoodpeckerSecret string
	// GroupsHeader is the oauth2-proxy header carrying Authentik group names.
	GroupsHeader string
	// AllowedGroups gates every page load and API call. Never empty.
	AllowedGroups []string
}

// Load resolves configuration from the environment, failing closed on an empty
// allow-list (an empty list would authorize nobody or, worse, be read as
// "anyone" by a future refactor).
func Load() (*Config, error) {
	c := &Config{
		Listen:              envOr("REPOSPAWNER_LISTEN", ":8080"),
		Namespace:           envOr("REPOSPAWNER_NAMESPACE", "repospawner"),
		Image:               envOr("REPOSPAWNER_IMAGE", ""),
		JobServiceAccount:   envOr("REPOSPAWNER_JOB_SERVICE_ACCOUNT", "repospawner"),
		GiteaURL:            envOr("GITEA_URL", "https://git.unkin.net"),
		TFGitRepo:           envOr("REPOSPAWNER_TFGIT_REPO", "unkin/terraform-git"),
		VaultAddr:           envOr("VAULT_ADDR", "https://vault.service.consul:8200"),
		VaultK8sMount:       envOr("REPOSPAWNER_VAULT_K8S_MOUNT", "k8s/au/syd1"),
		VaultK8sRole:        envOr("REPOSPAWNER_VAULT_K8S_ROLE", "repospawner"),
		VaultSATokenPath:    envOr("REPOSPAWNER_VAULT_SA_TOKEN_PATH", "/var/run/secrets/vault/token"),
		GiteaCredsPath:      envOr("REPOSPAWNER_GITEA_CREDS_PATH", "gitea/creds/repospawner"),
		WoodpeckerServer:    envOr("WOODPECKER_SERVER", "https://ci.k8s.syd1.au.unkin.net"),
		WoodpeckerTokenFile: envOr("REPOSPAWNER_WOODPECKER_TOKEN_FILE", "/etc/repospawner/woodpecker/token"),
		WoodpeckerSecret:    envOr("REPOSPAWNER_WOODPECKER_SECRET", "repospawner-woodpecker"),
		GroupsHeader:        envOr("REPOSPAWNER_GROUPS_HEADER", "X-Forwarded-Groups"),
		AllowedGroups:       ParseGroups(envOr("REPOSPAWNER_ALLOWED_GROUPS", "akP-repospawner-user")),
	}

	if len(c.AllowedGroups) == 0 {
		return nil, fmt.Errorf("REPOSPAWNER_ALLOWED_GROUPS must name at least one group")
	}
	if strings.TrimSpace(c.GroupsHeader) == "" {
		return nil, fmt.Errorf("REPOSPAWNER_GROUPS_HEADER must not be empty")
	}
	if strings.TrimSpace(c.Namespace) == "" {
		return nil, fmt.Errorf("REPOSPAWNER_NAMESPACE must not be empty")
	}
	if strings.TrimSpace(c.JobServiceAccount) == "" {
		return nil, fmt.Errorf("REPOSPAWNER_JOB_SERVICE_ACCOUNT must not be empty")
	}
	if strings.TrimSpace(c.VaultK8sMount) == "" || strings.TrimSpace(c.VaultK8sRole) == "" {
		return nil, fmt.Errorf("REPOSPAWNER_VAULT_K8S_MOUNT and REPOSPAWNER_VAULT_K8S_ROLE must not be empty")
	}
	if strings.TrimSpace(c.GiteaCredsPath) == "" {
		return nil, fmt.Errorf("REPOSPAWNER_GITEA_CREDS_PATH must not be empty")
	}
	if err := requireHTTP("GITEA_URL", c.GiteaURL); err != nil {
		return nil, err
	}
	if err := requireHTTP("VAULT_ADDR", c.VaultAddr); err != nil {
		return nil, err
	}
	if err := requireHTTP("WOODPECKER_SERVER", c.WoodpeckerServer); err != nil {
		return nil, err
	}
	if _, _, err := SplitRepo(c.TFGitRepo); err != nil {
		return nil, fmt.Errorf("REPOSPAWNER_TFGIT_REPO: %w", err)
	}
	return c, nil
}

// SplitRepo splits an "owner/name" reference.
func SplitRepo(s string) (owner, name string, err error) {
	owner, name, ok := strings.Cut(strings.TrimSpace(s), "/")
	if !ok || owner == "" || name == "" || strings.Contains(name, "/") {
		return "", "", fmt.Errorf("%q is not owner/name", s)
	}
	return owner, name, nil
}

// ParseGroups splits a group list tolerating both comma and whitespace
// separation, dropping empties. oauth2-proxy emits comma-separated groups but
// deployments hand-write the allow-list.
func ParseGroups(s string) []string {
	fields := strings.FieldsFunc(s, func(r rune) bool {
		return r == ',' || r == ' ' || r == '\t' || r == '\n' || r == '\r' || r == ';'
	})
	out := make([]string, 0, len(fields))
	for _, f := range fields {
		if f = strings.TrimSpace(f); f != "" {
			out = append(out, f)
		}
	}
	return out
}

func requireHTTP(name, val string) error {
	if !strings.HasPrefix(val, "http://") && !strings.HasPrefix(val, "https://") {
		return fmt.Errorf("%s %q must be an http(s) URL", name, val)
	}
	return nil
}

func envOr(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}