package provider

import (
	"fmt"
	"os"

	"sigs.k8s.io/yaml"
)

// Config is the top-level shape of the --providers-config file.
type Config struct {
	Providers []ProviderConfig `json:"providers"`
}

// ProviderConfig is one named, typed provider instance — e.g. "gcp-eu" and
// "gcp-us" can be two ProviderConfigs of Type "gcp" with different GCP
// blocks. Exactly one of the type-specific blocks below should be set,
// matching Type.
type ProviderConfig struct {
	Name       string            `json:"name"`
	Type       string            `json:"type"`
	Kubernetes *KubernetesConfig `json:"kubernetes,omitempty"`
	GCP        *GCPConfig        `json:"gcp,omitempty"`
}

// KubernetesConfig configures the kubernetes-pod provider, which creates
// proxy Pods in the same cluster the operator itself runs in.
type KubernetesConfig struct {
	// Image is the proxy container image. Default "ubuntu/squid:6.6-24.04_edge".
	Image string `json:"image,omitempty"`
}

// GCPConfig configures a named GCP provider instance.
type GCPConfig struct {
	// Project is the GCP project ID. Required.
	Project string `json:"project"`
	// Network is the VPC network name. Default "default".
	Network string `json:"network,omitempty"`
	// NetworkTag is the firewall/network tag applied to created instances.
	// Default "proxy-operator".
	NetworkTag string `json:"networkTag,omitempty"`
	// DiskSizeGB is the boot disk size in GB. Default 10.
	DiskSizeGB int64 `json:"diskSizeGb,omitempty"`
}

// LoadConfigFile reads and parses a providers-config file from disk.
func LoadConfigFile(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading providers config %s: %w", path, err)
	}
	return LoadConfig(data)
}

// LoadConfig parses and validates providers-config YAML. It fails fast:
// unknown provider types, duplicate names, and missing type-specific
// required fields are all load-time errors here, not runtime surprises
// discovered only when a provider is actually used.
func LoadConfig(data []byte) (*Config, error) {
	var cfg Config
	if err := yaml.UnmarshalStrict(data, &cfg); err != nil {
		return nil, fmt.Errorf("parsing providers config: %w", err)
	}
	if err := cfg.validate(); err != nil {
		return nil, fmt.Errorf("validating providers config: %w", err)
	}
	return &cfg, nil
}

func (c *Config) validate() error {
	if len(c.Providers) == 0 {
		return fmt.Errorf("providers: at least one provider must be configured")
	}
	seen := make(map[string]bool, len(c.Providers))
	for i, p := range c.Providers {
		if p.Name == "" {
			return fmt.Errorf("providers[%d]: name is required", i)
		}
		if seen[p.Name] {
			return fmt.Errorf("providers[%d]: duplicate provider name %q", i, p.Name)
		}
		seen[p.Name] = true

		switch p.Type {
		case "kubernetes":
			if p.GCP != nil {
				return fmt.Errorf("providers[%d] %q: type is kubernetes but a gcp block is set", i, p.Name)
			}
		case "gcp":
			if p.Kubernetes != nil {
				return fmt.Errorf("providers[%d] %q: type is gcp but a kubernetes block is set", i, p.Name)
			}
			if p.GCP == nil || p.GCP.Project == "" {
				return fmt.Errorf("providers[%d] %q: gcp.project is required", i, p.Name)
			}
		case "":
			return fmt.Errorf("providers[%d] %q: type is required", i, p.Name)
		default:
			return fmt.Errorf("providers[%d] %q: unknown provider type %q", i, p.Name, p.Type)
		}
	}
	return nil
}