package routing_test

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"net/http/httptest"
	"sync"
	"testing"
	"time"

	"github.com/mathiasbq/supervisor/internal/routing"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

type fakeLLM struct {
	mu    sync.Mutex
	calls []struct{ Model, System, User string }
	resp  string
	err   error
	errOn string // if non-empty, only the named model errors
}

func (f *fakeLLM) Complete(_ context.Context, model, system, user string) (string, int64, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	f.calls = append(f.calls, struct{ Model, System, User string }{model, system, user})
	if f.errOn == model {
		return "", 0, f.err
	}
	if f.err != nil && f.errOn == "" {
		return "", 0, f.err
	}
	return f.resp, 100, nil
}

func newRouter(t *testing.T, llm *fakeLLM, passRate float64) (*routing.Router, *httptest.Server, *httptest.Server) {
	t.Helper()
	brain := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.URL.Path {
		case "/pass-rate":
			_ = json.NewEncoder(w).Encode(map[string]any{"pass_rate": passRate})
		case "/mcp":
			_ = json.NewEncoder(w).Encode(map[string]any{"jsonrpc": "2.0", "id": 1, "result": map[string]any{}})
		}
	}))
	t.Cleanup(brain.Close)

	r := &routing.Router{
		Fetcher:       routing.NewFetcher(brain.URL, "7d", time.Minute),
		Logger:        routing.NewLogger(brain.URL),
		Policy:        routing.Policy{Floor: 0.9, Ceil: 0.7},
		FastModel:     "koala/qwen35-9b-fast",
		ThinkingModel: "iguana/gemma4-26b",
		Complete:      llm.Complete,
	}
	return r, brain, brain
}

func TestRouterRoutesLocalAtHighPassRate(t *testing.T) {
	llm := &fakeLLM{resp: "ok"}
	r, _, _ := newRouter(t, llm, 0.95)

	out, _, err := r.Run(context.Background(), routing.RunInput{
		Skill: "review", System: "sys", User: "user", SessionID: "s1", ProjectRoot: "/p",
	})
	require.NoError(t, err)
	assert.Equal(t, "ok", out)

	llm.mu.Lock()
	defer llm.mu.Unlock()
	require.Len(t, llm.calls, 1)
	assert.Equal(t, "koala/qwen35-9b-fast", llm.calls[0].Model)
}

func TestRouterRoutesThinkingAtLowPassRate(t *testing.T) {
	llm := &fakeLLM{resp: "ok"}
	r, _, _ := newRouter(t, llm, 0.3)

	_, _, err := r.Run(context.Background(), routing.RunInput{
		Skill: "review", System: "sys", User: "user", SessionID: "s2",
	})
	require.NoError(t, err)

	llm.mu.Lock()
	defer llm.mu.Unlock()
	require.Len(t, llm.calls, 1)
	assert.Equal(t, "iguana/gemma4-26b", llm.calls[0].Model)
}

func TestRouterFailsOpenFastErrorToThinking(t *testing.T) {
	llm := &fakeLLM{resp: "ok-after-fallback", err: errors.New("fast boom"), errOn: "koala/qwen35-9b-fast"}
	r, _, _ := newRouter(t, llm, 0.95) // would route fast

	out, _, err := r.Run(context.Background(), routing.RunInput{
		Skill: "review", System: "sys", User: "user", SessionID: "s3",
	})
	require.NoError(t, err)
	assert.Equal(t, "ok-after-fallback", out)

	llm.mu.Lock()
	defer llm.mu.Unlock()
	require.Len(t, llm.calls, 2)
	assert.Equal(t, "koala/qwen35-9b-fast", llm.calls[0].Model)
	assert.Equal(t, "iguana/gemma4-26b", llm.calls[1].Model)
}

func TestRouterDefaultsToFastWhenBrainUnreachable(t *testing.T) {
	// Brain returns 500 → fetcher errors → router treats pass rate as nil → fast.
	brain := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		http.Error(w, "down", http.StatusInternalServerError)
	}))
	defer brain.Close()

	llm := &fakeLLM{resp: "ok"}
	r := &routing.Router{
		Fetcher:       routing.NewFetcher(brain.URL, "7d", time.Minute),
		Logger:        routing.NewLogger(brain.URL),
		Policy:        routing.Policy{Floor: 0.9, Ceil: 0.7},
		FastModel:     "koala/qwen35-9b-fast",
		ThinkingModel: "iguana/gemma4-26b",
		Complete:      llm.Complete,
	}

	_, _, err := r.Run(context.Background(), routing.RunInput{
		Skill: "review", System: "sys", User: "user", SessionID: "s4",
	})
	require.NoError(t, err)

	llm.mu.Lock()
	defer llm.mu.Unlock()
	require.Len(t, llm.calls, 1)
	assert.Equal(t, "koala/qwen35-9b-fast", llm.calls[0].Model)
}