package provision

import (
	"fmt"
	"time"

	"github.com/carlosframework/platform/internal/release"
)

// InstallRequest is one "Update now" (spec §4.2).
type InstallRequest struct {
	ID        uint64    `json:"id"`
	FastTrack bool      `json:"fast_track,omitempty"`
	At        time.Time `json:"at"`
	By        string    `json:"by,omitempty"`
}

// UpdatePolicy is the app's instance update policy (spec §3.2). The default
// channel is the manifest's own Channel (index Q4).
type UpdatePolicy struct {
	InstanceControl []string `json:"instance_control,omitempty"`
	DefaultUpdates  string   `json:"default_updates,omitempty"`
	DefaultMajor    *int     `json:"default_major,omitempty"`
}

// EffectiveUpdates resolves one instance's settings: its own explicit values,
// else the app's defaults, else today's. A major hold off stable is dropped:
// only stable promotions cut tags (spec §3.1), so it could never hold.
func EffectiveUpdates(rec Record, p *UpdatePolicy) release.UpdateSettings {
	u := release.UpdateSettings{Updates: release.UpdatesAuto, Channel: rec.Channel, Pin: rec.Pin}
	if p != nil {
		if p.DefaultUpdates != "" {
			u.Updates = p.DefaultUpdates
		}
		u.Major = p.DefaultMajor
		u.Control = append([]string(nil), p.InstanceControl...)
	}
	if rec.Updates != "" {
		u.Updates = rec.Updates
	}
	if rec.Major != nil {
		u.Major = rec.Major
	}
	if u.Channel != "stable" {
		u.Major = nil
	}
	if rec.InstallRequest != nil {
		u.InstallRequest, u.InstallFastTrack = rec.InstallRequest.ID, rec.InstallRequest.FastTrack
	}
	return u
}

// ValidateUpdates is the record's door check (the console's PUT).
func ValidateUpdates(rec Record) error {
	if rec.Updates != "" && rec.Updates != release.UpdatesAuto && rec.Updates != release.UpdatesManual {
		return fmt.Errorf("updates must be auto or manual")
	}
	if rec.Major != nil && *rec.Major < 0 {
		return fmt.Errorf("major must be a whole number, 0 or more")
	}
	if rec.Major != nil && rec.Channel != "stable" {
		return fmt.Errorf("major applies only to the stable channel")
	}
	if rec.Pin != "" && (!release.ValidVersion(rec.Pin) || rec.Pin == "dev") {
		return fmt.Errorf("invalid pin %q", rec.Pin)
	}
	return nil
}

// ValidatePolicy is the app policy's door check.
func ValidatePolicy(p *UpdatePolicy) error {
	if p == nil {
		return nil
	}
	if !release.ValidControl(p.InstanceControl) {
		return fmt.Errorf("instance_control must name updates, channel, major or pin, each once")
	}
	if p.DefaultUpdates != "" && p.DefaultUpdates != release.UpdatesAuto && p.DefaultUpdates != release.UpdatesManual {
		return fmt.Errorf("default_updates must be auto or manual")
	}
	if p.DefaultMajor != nil && *p.DefaultMajor < 0 {
		return fmt.Errorf("default_major must be a whole number, 0 or more")
	}
	return nil
}