// Package servicedef handles parsing and writing TOML service definition files.
package servicedef

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	toml "github.com/pelletier/go-toml/v2"

	mcpv1 "git.wntrmute.dev/mc/mcp/gen/mcp/v1"
)

// ServiceDef is the top-level TOML structure for a service definition file.
type ServiceDef struct {
	Name       string         `toml:"name"`
	Node       string         `toml:"node"`
	Active     *bool          `toml:"active,omitempty"`
	Path       string         `toml:"path,omitempty"`
	Build      *BuildDef      `toml:"build,omitempty"`
	Components []ComponentDef `toml:"components"`
}

// BuildDef describes how to build container images for a service.
type BuildDef struct {
	Images   map[string]string `toml:"images"`
	UsesMCDSL bool            `toml:"uses_mcdsl,omitempty"`
}

// RouteDef describes a route for a component, used for automatic port
// allocation and mc-proxy integration.
type RouteDef struct {
	Name     string `toml:"name,omitempty"`
	Port     int    `toml:"port"`
	Mode     string `toml:"mode,omitempty"`
	Hostname string `toml:"hostname,omitempty"`
}

// ComponentDef describes a single container component within a service.
type ComponentDef struct {
	Name    string     `toml:"name"`
	Image   string     `toml:"image"`
	Network string     `toml:"network,omitempty"`
	User    string     `toml:"user,omitempty"`
	Restart string     `toml:"restart,omitempty"`
	Ports   []string   `toml:"ports,omitempty"`
	Volumes []string   `toml:"volumes,omitempty"`
	Cmd     []string   `toml:"cmd,omitempty"`
	Routes  []RouteDef `toml:"routes,omitempty"`
	Env     []string   `toml:"env,omitempty"`
}

// Load reads and parses a TOML service definition file. If the active field
// is omitted, it defaults to true.
func Load(path string) (*ServiceDef, error) {
	data, err := os.ReadFile(path) //nolint:gosec // path from trusted config dir
	if err != nil {
		return nil, fmt.Errorf("read service def %q: %w", path, err)
	}

	var def ServiceDef
	if err := toml.Unmarshal(data, &def); err != nil {
		return nil, fmt.Errorf("parse service def %q: %w", path, err)
	}

	if err := validate(&def); err != nil {
		return nil, fmt.Errorf("validate service def %q: %w", path, err)
	}

	if def.Active == nil {
		t := true
		def.Active = &t
	}

	return &def, nil
}

// Write serializes a ServiceDef to TOML and writes it to the given path
// with 0644 permissions. Parent directories are created if needed.
func Write(path string, def *ServiceDef) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil { //nolint:gosec // service defs are non-secret
		return fmt.Errorf("create parent dirs for %q: %w", path, err)
	}

	data, err := toml.Marshal(def)
	if err != nil {
		return fmt.Errorf("marshal service def: %w", err)
	}

	if err := os.WriteFile(path, data, 0o644); err != nil { //nolint:gosec // service defs are non-secret
		return fmt.Errorf("write service def %q: %w", path, err)
	}

	return nil
}

// LoadAll reads all .toml files from dir, parses each one, and returns the
// list sorted by service name.
func LoadAll(dir string) ([]*ServiceDef, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, fmt.Errorf("read service dir %q: %w", dir, err)
	}

	var defs []*ServiceDef
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".toml") {
			continue
		}
		def, err := Load(filepath.Join(dir, e.Name()))
		if err != nil {
			return nil, err
		}
		defs = append(defs, def)
	}

	sort.Slice(defs, func(i, j int) bool {
		return defs[i].Name < defs[j].Name
	})

	return defs, nil
}

// validate checks that a ServiceDef has all required fields and that
// component names are unique.
func validate(def *ServiceDef) error {
	if def.Name == "" {
		return fmt.Errorf("service name is required")
	}
	if def.Node == "" {
		return fmt.Errorf("service node is required")
	}
	if len(def.Components) == 0 {
		return fmt.Errorf("service %q must have at least one component", def.Name)
	}

	seen := make(map[string]bool)
	for _, c := range def.Components {
		if c.Name == "" {
			return fmt.Errorf("component name is required in service %q", def.Name)
		}
		if c.Image == "" {
			return fmt.Errorf("component %q image is required in service %q", c.Name, def.Name)
		}
		if seen[c.Name] {
			return fmt.Errorf("duplicate component name %q in service %q", c.Name, def.Name)
		}
		seen[c.Name] = true

		if err := validateRoutes(c.Name, def.Name, c.Routes); err != nil {
			return err
		}
	}

	return nil
}

// validateRoutes checks that routes within a component are valid.
func validateRoutes(compName, svcName string, routes []RouteDef) error {
	if len(routes) == 0 {
		return nil
	}

	routeNames := make(map[string]bool)
	for i, r := range routes {
		if r.Port <= 0 {
			return fmt.Errorf("route port must be > 0 in component %q of service %q", compName, svcName)
		}
		if r.Mode != "" && r.Mode != "l4" && r.Mode != "l7" {
			return fmt.Errorf("route mode must be \"l4\" or \"l7\" in component %q of service %q", compName, svcName)
		}
		if len(routes) > 1 && r.Name == "" {
			return fmt.Errorf("route name is required when component has multiple routes in component %q of service %q", compName, svcName)
		}

		// Use index-based key for unnamed single routes.
		key := r.Name
		if key == "" {
			key = fmt.Sprintf("_route_%d", i)
		}
		if routeNames[key] {
			return fmt.Errorf("duplicate route name %q in component %q of service %q", r.Name, compName, svcName)
		}
		routeNames[key] = true
	}
	return nil
}

// ToProto converts a ServiceDef to a proto ServiceSpec.
func ToProto(def *ServiceDef) *mcpv1.ServiceSpec {
	spec := &mcpv1.ServiceSpec{
		Name:   def.Name,
		Active: def.Active != nil && *def.Active,
	}

	for _, c := range def.Components {
		cs := &mcpv1.ComponentSpec{
			Name:    c.Name,
			Image:   c.Image,
			Network: c.Network,
			User:    c.User,
			Restart: c.Restart,
			Ports:   c.Ports,
			Volumes: c.Volumes,
			Cmd:     c.Cmd,
			Env:     c.Env,
		}
		for _, r := range c.Routes {
			cs.Routes = append(cs.Routes, &mcpv1.RouteSpec{
				Name:     r.Name,
				Port:     int32(r.Port),
				Mode:     r.Mode,
				Hostname: r.Hostname,
			})
		}
		spec.Components = append(spec.Components, cs)
	}

	return spec
}

// FromProto converts a proto ServiceSpec back to a ServiceDef. The node
// parameter is required because ServiceSpec does not include the node field
// (it is a CLI-side routing concern).
func FromProto(spec *mcpv1.ServiceSpec, node string) *ServiceDef {
	active := spec.GetActive()
	def := &ServiceDef{
		Name:   spec.GetName(),
		Node:   node,
		Active: &active,
	}

	for _, c := range spec.GetComponents() {
		cd := ComponentDef{
			Name:    c.GetName(),
			Image:   c.GetImage(),
			Network: c.GetNetwork(),
			User:    c.GetUser(),
			Restart: c.GetRestart(),
			Ports:   c.GetPorts(),
			Volumes: c.GetVolumes(),
			Cmd:     c.GetCmd(),
			Env:     c.GetEnv(),
		}
		for _, r := range c.GetRoutes() {
			cd.Routes = append(cd.Routes, RouteDef{
				Name:     r.GetName(),
				Port:     int(r.GetPort()),
				Mode:     r.GetMode(),
				Hostname: r.GetHostname(),
			})
		}
		def.Components = append(def.Components, cd)
	}

	return def
}