package buildstep

import (
	"context"
	"encoding/json"
	"fmt"

	"git.novox.be/novox/mesh-sdk/go/delivery"
)

// Guard is a build module's check that the toolchain installed on its node is the one its recipe builds with
// (novox/hq ADR 0469 §1; issue 1473). The same guard serves ADR 0470 §4's postgres major for the integration
// level, with its own Probe and Want.
type Guard struct {
	// Language is the toolchain's key part: go or typescript (delivery.ToolchainKey).
	Language string
	// Want is the toolchain version the recipe builds with, and Recipe the recipe's own version. The indexer
	// compares both texts as they are written here.
	Want, Recipe string
	// Probe reads the installed version (go version, node --version).
	Probe func(ctx context.Context) (installed string, err error)
	Node  string
	// Put is the toolchains state's Put (stdio.State(delivery.ToolchainsState).Put).
	Put Put
}

// Check probes the installed version, writes it to <node>.<language> of the toolchains state every time it runs,
// and answers nil when it is the recipe's. Otherwise it answers a *Refusal naming both versions; the installed
// version is written even then, so the indexer sees that builders disagree. A probe that fails is a *Refusal
// naming its failure, and nothing is written. A write that fails is an error that is not a Refusal.
func (g Guard) Check(ctx context.Context) error {
	installed, err := g.Probe(ctx)
	if err != nil {
		return &Refusal{Text: fmt.Sprintf("the installed %s version could not be read: %v", g.Language, err), Want: g.Want}
	}
	key, err := delivery.ToolchainKey(g.Node, g.Language)
	if err != nil {
		return err
	}
	raw, err := delivery.EncodeToolchain(delivery.Toolchain{Language: g.Language, Version: installed, Recipe: g.Recipe, At: now().UTC()})
	if err != nil {
		return err
	}
	if _, err := g.Put(key, json.RawMessage(raw)); err != nil {
		return fmt.Errorf("buildstep: writing the toolchain %s: %w", key, err)
	}
	if installed != g.Want {
		return &Refusal{Text: fmt.Sprintf("%s %s installed, the recipe builds with %s %s", g.Language, installed, g.Language, g.Want),
			Want: g.Want, Have: installed}
	}
	return nil
}