package exec

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// ChainEntry is one tier in an escalation chain.
type ChainEntry struct {
	Model   string // e.g. "ollama/phi4", "claude-sonnet-4-6"
	Tier    string // "local" | "subagent" | "managed"
	IsCloud bool   // true for claude-* models; skips verifier call
}

// EntryFor builds a ChainEntry from a model name string.
func EntryFor(model string) ChainEntry {
	cloud := strings.HasPrefix(model, "claude-")
	tier := "local"
	if cloud {
		tier = "subagent"
	}
	return ChainEntry{Model: model, Tier: tier, IsCloud: cloud}
}

// AttemptRecord captures the outcome of one tier attempt for session logging.
type AttemptRecord struct {
	Model      string
	Tier       string
	DurationMs int64
	WarmStart  bool
	Verdict    string // "accept" | "escalate" | "error"
	Feedback   string
}

// VerifierFn is the interface the orchestrator uses to verify local output.
type VerifierFn interface {
	Verify(ctx context.Context, skillPrompt, taskPrompt string, output Result) (Verdict, error)
}

// ExecutorRunFn is the signature of Executor.Run and LiteLLMExecutor.Run.
type ExecutorRunFn func(ctx context.Context, req Request) (Result, error)

// Orchestrator walks an escalation chain, delegating generation and verification.
// It implements the ExecutorFn shape expected by skill handlers.
type Orchestrator struct {
	chain        []ChainEntry
	localRun     ExecutorRunFn // for local (non-cloud) tiers; may be nil
	cloudRun     ExecutorRunFn // for cloud tiers; may be nil
	verifier     VerifierFn
	llamaSwapURL string
	attempts     *[]AttemptRecord
}

// NewOrchestrator creates an Orchestrator.
// attempts is a pointer to a slice that will be appended to on each tier attempt.
// Pass nil for localRun or cloudRun if no tiers of that type exist in the chain.
func NewOrchestrator(
	chain []ChainEntry,
	localRun ExecutorRunFn,
	cloudRun ExecutorRunFn,
	verifier VerifierFn,
	llamaSwapURL string,
	attempts *[]AttemptRecord,
) *Orchestrator {
	return &Orchestrator{
		chain:        chain,
		localRun:     localRun,
		cloudRun:     cloudRun,
		verifier:     verifier,
		llamaSwapURL: llamaSwapURL,
		attempts:     attempts,
	}
}

// Run walks the escalation chain and returns the first accepted result.
// Satisfies the ExecutorFn signature: func(context.Context, Request) (Result, error).
func (o *Orchestrator) Run(ctx context.Context, req Request) (Result, error) {
	taskPrompt := req.TaskPrompt

	for _, entry := range o.chain {
		warm := o.probeWarm(entry.Model)
		start := time.Now()

		tierReq := req
		tierReq.Model = entry.Model
		tierReq.TaskPrompt = taskPrompt

		if entry.IsCloud {
			result, genErr := o.cloudRun(ctx, tierReq)
			dur := time.Since(start).Milliseconds()
			verdict := "accept"
			if genErr != nil {
				verdict = "error"
			}
			o.appendAttempt(AttemptRecord{
				Model:      entry.Model,
				Tier:       entry.Tier,
				DurationMs: dur,
				WarmStart:  warm,
				Verdict:    verdict,
			})
			if genErr == nil {
				return result, nil
			}
			continue
		}

		// Local tier.
		result, genErr := o.localRun(ctx, tierReq)
		dur := time.Since(start).Milliseconds()

		if genErr != nil {
			o.appendAttempt(AttemptRecord{
				Model:      entry.Model,
				Tier:       entry.Tier,
				DurationMs: dur,
				WarmStart:  warm,
				Verdict:    "error",
				Feedback:   genErr.Error(),
			})
			continue
		}

		verdict, verErr := o.verifier.Verify(ctx, req.SkillPrompt, taskPrompt, result)
		if verErr != nil {
			// Treat verifier failure as escalate (safe default).
			o.appendAttempt(AttemptRecord{
				Model:      entry.Model,
				Tier:       entry.Tier,
				DurationMs: dur,
				WarmStart:  warm,
				Verdict:    "escalate",
				Feedback:   "verifier error: " + verErr.Error(),
			})
			continue
		}

		if verdict.Accept {
			o.appendAttempt(AttemptRecord{
				Model:      entry.Model,
				Tier:       entry.Tier,
				DurationMs: dur,
				WarmStart:  warm,
				Verdict:    "accept",
			})
			return result, nil
		}

		o.appendAttempt(AttemptRecord{
			Model:      entry.Model,
			Tier:       entry.Tier,
			DurationMs: dur,
			WarmStart:  warm,
			Verdict:    "escalate",
			Feedback:   verdict.Feedback,
		})
		// Inject verifier feedback into the next tier's task prompt.
		taskPrompt = taskPrompt + "\n\nPrior attempt feedback: " + verdict.Feedback
	}

	return Result{}, fmt.Errorf("all tiers exhausted after %d attempt(s)", len(o.chain))
}

func (o *Orchestrator) appendAttempt(rec AttemptRecord) {
	if o.attempts != nil {
		*o.attempts = append(*o.attempts, rec)
	}
}

// probeWarm checks whether the model is currently loaded in llama-swap.
// Returns false on any error or if llamaSwapURL is empty.
func (o *Orchestrator) probeWarm(model string) bool {
	if o.llamaSwapURL == "" {
		return false
	}
	ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, o.llamaSwapURL+"/v1/models", nil)
	if err != nil {
		return false
	}
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return false
	}
	defer resp.Body.Close() //nolint:errcheck
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return false
	}
	return strings.Contains(string(body), model)
}