package runtime

import (
	"github.com/krow/krow-backend/go-api/internal/config"
	"github.com/krow/krow-backend/go-api/internal/gateway"
	"github.com/krow/krow-backend/go-api/internal/knowledge"
	"github.com/krow/krow-backend/go-api/internal/repo"
	"github.com/krow/krow-backend/go-api/internal/tools"
)

// NewModelEngine builds the production runtime: the loader, the agent loop, a
// live model gateway and a Postgres trajectory sink.
//
// One call, because the alternative is four, and four assembled at a call site
// is how a deployment ends up running with a DiscardSink nobody chose. A test
// that wants a fake model still reaches for NewEngine with WithAgentExecutor —
// this function is the wiring, not a second way to configure the runtime.
//
// Skills keep the refusing stub. A skill has no executor of its own: the loop
// runs agents, and a skill reaches a model only as a capability an agent
// carries. Handing SkillExec a model would create a second, unbounded path to
// one — which is exactly the shape I3 exists to prevent.
func NewModelEngine(db repo.Querier, cfg config.Config) *Engine {
	gw := gateway.NewAnthropic(gateway.FromConfig(cfg.Model))
	retriever := knowledge.NewRetriever(db, NewEmbedder(cfg))
	exec := NewModelExecutor(gw, NewPostgresSink(db), DefaultTools(db, retriever)).
		WithRetriever(retriever)
	return NewEngine(db, WithAgentExecutor(exec))
}

// NewEmbedder picks the embedding provider from configuration.
//
// Explicit first, then what is configured, then nothing. The order is the whole
// design: three providers all return vectors and retrieval works with any of
// them, so a deployment running the wrong one looks identical to one running
// the right one until somebody phrases a question differently. Naming the
// provider is how that stops being a silent condition.
//
//	ollama    A model on this machine. Real semantics, no credential, no
//	          per-token cost, no tenant text leaving the host. The default
//	          worth reaching for.
//	voyage    Hosted. Better on subtle retrieval over a large messy corpus,
//	          and the only one that needs a credential.
//	lexical   The deterministic stand-in. NOT semantic — it matches shared
//	          vocabulary and nothing else. Development only; config.validate
//	          refuses it in production.
//
// Returns nil when nothing is configured, and retrieval then runs keyword-only,
// saying so on every result. Nil rather than a hosted client with an empty key:
// both end up keyword-only, but nil says "no embedder is configured" once, at
// wiring time, instead of failing an HTTP call per query to learn the same
// thing.
func NewEmbedder(cfg config.Config) knowledge.Embedder {
	k := cfg.Knowledge

	provider := k.EmbedProvider
	if provider == "" {
		// Nothing named. Infer from what is actually present, preferring the
		// one that costs nothing and keeps text local.
		switch {
		case k.UseLexicalEmbedder:
			provider = "lexical"
		case k.EmbedBaseURL != "":
			provider = "ollama"
		case k.EmbedAPIKey != "":
			provider = "voyage"
		default:
			return nil
		}
	}

	switch provider {
	case "ollama":
		return knowledge.NewOllama(k.EmbedBaseURL, k.EmbedModel, k.EmbedDims)

	case "voyage":
		if k.EmbedAPIKey == "" {
			// Named but unusable. Nil, so retrieval degrades honestly rather
			// than failing a request per query on a credential nobody set.
			return nil
		}
		model, dims := k.EmbedModel, k.EmbedDims
		if model == "" {
			model = knowledge.DefaultVoyageModel
		}
		if dims == 0 {
			dims = knowledge.DefaultVoyageDims
		}
		return knowledge.NewVoyage(k.EmbedAPIKey, model, dims)

	case "lexical":
		dims := k.EmbedDims
		if dims == 0 {
			dims = 256
		}
		e := knowledge.NewLexical(dims)
		// Told what environment it is in, so its own refusal is the backstop
		// behind config.validate's.
		e.Production = cfg.AppEnv == "production"
		return e
	}
	return nil
}

// DefaultTools is the tool registry this service ships with.
//
// One function, so "which tools exist" has a single answer that a test and the
// server reach the same way. Registration panics on a malformed tool: a
// service that booted without a capability its specs name would fail one run
// at a time instead of once, loudly, at startup.
func DefaultTools(db repo.Querier, retriever *knowledge.Retriever) *tools.Registry {
	// The confirmation store is Postgres-backed, not in-process. A pending
	// write is asked about in one request and approved in another, and nothing
	// guarantees those two reach the same replica — an in-memory store would
	// refuse a large share of perfectly good approvals, for a reason invisible
	// to the person clicking. See tools.MemoryStore's own warning.
	reg := tools.NewRegistryWithStore(tools.NewPostgresStore(db))
	for _, t := range []tools.Tool{
		// Activity
		tools.ActivityBreakdown(db),
		tools.ActivitySignals(db),
		// Workforce
		tools.WorkforceAttendance(db),
		tools.WorkforceOvertime(db),
		tools.WorkforceCoverage(db),
		tools.WorkforceTraining(db),
		// Hiring
		tools.CandidatesQuality(db),
		tools.HiresRecent(db),
		tools.HiresPerformance(db),
		tools.PositionsRisk(db),
		tools.TalentPool(db),
		// Cross-domain
		tools.WorkspaceSummary(db),
		tools.OperationsRisk(db),
		// Assignments: the two lookups that yield ids, and the one write that
		// consumes them. assign_worker is the only tool here with an effect,
		// and it cannot run without an approval — see tools/confirm.go.
		tools.OpenPositions(db),
		tools.AvailableWorkers(db),
		tools.AssignWorker(db),
		// The hiring funnel: the lookup that yields application ids, and the
		// write that moves somebody through it. Replaces the browser panel's
		// interview matcher, which was the one capability the old templates had
		// that the tool layer did not.
		tools.CandidatesAwaiting(db),
		tools.MoveApplication(db),
		// Knowledge. Registered once; which corpora it may read comes from the
		// running agent's spec by way of the tool Context, so this single
		// registration serves every agent without any of them being able to
		// name another's documents.
		tools.KnowledgeSearch(retriever),
	} {
		reg.MustRegister(t)
	}
	return reg
}