package localapi

import (
	"context"
	"encoding/json"
	"net/http"
	"sync"
	"testing"

	"gitea.dooplex.hu/admin/felhom-agent/internal/proxmox"
)

// fakeMemory is a MemoryOps fake: it holds the guest's allocation/usage + host total, counts
// SetConfig calls (so refusals can prove the non-effect), and — when applyReflect is set — makes a
// SetConfig update the observed maxmem so the post-apply verify read passes.
type fakeMemory struct {
	mu           sync.Mutex
	allocMB      int64
	usageBytes   int64
	maxmemBytes  int64
	hostTotalB   int64
	status       string
	setCalls     int
	lastParams   map[string]string
	setUPID      string
	setErr       error
	applyReflect bool
}

func (f *fakeMemory) GuestConfig(_ context.Context, _ int) (proxmox.GuestConfig, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	return proxmox.GuestConfig{Memory: f.allocMB}, nil
}
func (f *fakeMemory) GuestStatus(_ context.Context, vmid int) (proxmox.Guest, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	return proxmox.Guest{VMID: vmid, Mem: f.usageBytes, MaxMem: f.maxmemBytes, Status: f.status}, nil
}
func (f *fakeMemory) NodeStatus(_ context.Context) (proxmox.NodeStatus, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	var ns proxmox.NodeStatus
	ns.Memory.Total = f.hostTotalB
	return ns, nil
}
func (f *fakeMemory) SetConfig(_ context.Context, _ int, params map[string]string) (string, error) {
	f.mu.Lock()
	defer f.mu.Unlock()
	f.setCalls++
	f.lastParams = params
	if f.setErr != nil {
		return "", f.setErr
	}
	if f.applyReflect {
		if mb, ok := params["memory"]; ok {
			var v int64
			for _, c := range mb {
				v = v*10 + int64(c-'0')
			}
			f.allocMB = v
			f.maxmemBytes = v * mib
		}
	}
	return f.setUPID, nil
}
func (f *fakeMemory) WaitTask(_ context.Context, _ string, _ proxmox.WaitOptions) (proxmox.TaskStatus, error) {
	return proxmox.TaskStatus{Status: "stopped", ExitStatus: "OK"}, nil
}
func (f *fakeMemory) calls() int { f.mu.Lock(); defer f.mu.Unlock(); return f.setCalls }

// memServer builds a valid server with the memory fake wired and token "A" → guest 8200.
func memServer(t *testing.T, f *fakeMemory) *Server {
	t.Helper()
	s := newTestServerS(t, &fakeGuests{}, &fakeBackups{}, &fakeStore{}, nil)
	s.mem = f
	return s
}

// stdFixture: allocated 8192 MB, usage 3000 MB, host_total 16384 MB, running.
func stdFixture() *fakeMemory {
	return &fakeMemory{
		allocMB:      8192,
		usageBytes:   3000 * mib,
		maxmemBytes:  8192 * mib,
		hostTotalB:   16384 * mib,
		status:       "running",
		applyReflect: true,
	}
}

type memResp struct {
	OK   bool `json:"ok"`
	Data struct {
		VMID        int    `json:"vmid"`
		AllocatedMB int64  `json:"allocated_mb"`
		UsageMB     int64  `json:"usage_mb"`
		HostTotalMB int64  `json:"host_total_mb"`
		MinMB       int64  `json:"min_mb"`
		MaxMB       int64  `json:"max_mb"`
		FloorMB     int64  `json:"floor_mb"`
		Running     bool   `json:"running"`
		Code        string `json:"code"`
		OldMB       int64  `json:"old_mb"`
		NewMB       int64  `json:"new_mb"`
		Unchanged   bool   `json:"unchanged"`
	} `json:"data"`
	Error string `json:"error"`
}

func decodeMem(t *testing.T, body []byte) memResp {
	t.Helper()
	var m memResp
	if err := json.Unmarshal(body, &m); err != nil {
		t.Fatalf("decode response %q: %v", body, err)
	}
	return m
}

// Scenario C — GET /guest/memory: every field agent-computed, in MB.
func TestGuestMemory_GET(t *testing.T) {
	f := stdFixture()
	h := memServer(t, f).Handler()
	w := do(t, h, "GET", "/guest/memory", "A", "")
	if w.Code != 200 {
		t.Fatalf("GET = %d (%s), want 200", w.Code, w.Body.String())
	}
	d := decodeMem(t, w.Body.Bytes()).Data
	if d.AllocatedMB != 8192 || d.UsageMB != 3000 || d.HostTotalMB != 16384 ||
		d.MinMB != 2048 || d.MaxMB != 14336 || d.FloorMB != 3512 || !d.Running {
		t.Errorf("GET fields wrong: %+v", d)
	}
}

// Scenario A — grow + shrink happy paths: exactly one SetConfig, correct param, success.
func TestGuestMemory_GrowAndShrink(t *testing.T) {
	t.Run("grow", func(t *testing.T) {
		f := stdFixture()
		h := memServer(t, f).Handler()
		w := do(t, h, "POST", "/guest/memory", "A", `{"memory_mb":12288}`)
		if w.Code != 200 {
			t.Fatalf("grow = %d (%s), want 200", w.Code, w.Body.String())
		}
		d := decodeMem(t, w.Body.Bytes()).Data
		if d.OldMB != 8192 || d.NewMB != 12288 {
			t.Errorf("grow result = %+v", d)
		}
		if f.calls() != 1 {
			t.Errorf("SetConfig calls = %d, want 1", f.calls())
		}
		if f.lastParams["memory"] != "12288" {
			t.Errorf("SetConfig param = %q, want 12288", f.lastParams["memory"])
		}
	})
	t.Run("shrink above floor", func(t *testing.T) {
		f := stdFixture() // floor = max(2048, 3000+512) = 3512
		h := memServer(t, f).Handler()
		w := do(t, h, "POST", "/guest/memory", "A", `{"memory_mb":4096}`)
		if w.Code != 200 {
			t.Fatalf("shrink = %d (%s), want 200 (4096 >= floor 3512)", w.Code, w.Body.String())
		}
		if f.calls() != 1 {
			t.Errorf("SetConfig calls = %d, want 1", f.calls())
		}
	})
}

// Scenario B — the ruled refusals: 412 with the code, and SetConfig NEVER called.
func TestGuestMemory_Refusals(t *testing.T) {
	cases := []struct {
		name, body, code string
	}{
		{"below_min", `{"memory_mb":1024}`, "below_min"},
		{"above_max", `{"memory_mb":15000}`, "above_max"},
		{"below_usage_floor", `{"memory_mb":3300}`, "below_usage_floor"},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			f := stdFixture()
			h := memServer(t, f).Handler()
			w := do(t, h, "POST", "/guest/memory", "A", c.body)
			if w.Code != http.StatusPreconditionFailed {
				t.Fatalf("%s = %d (%s), want 412", c.name, w.Code, w.Body.String())
			}
			d := decodeMem(t, w.Body.Bytes()).Data
			if d.Code != c.code {
				t.Errorf("code = %q, want %q", d.Code, c.code)
			}
			if f.calls() != 0 {
				t.Errorf("SetConfig called %d times on a refusal — must be 0", f.calls())
			}
			// The refusal carries fresh bounds so the UI re-renders honestly.
			if d.MinMB != 2048 || d.MaxMB != 14336 || d.FloorMB != 3512 {
				t.Errorf("refusal bounds wrong: min=%d max=%d floor=%d", d.MinMB, d.MaxMB, d.FloorMB)
			}
			if c.code == "below_usage_floor" && d.UsageMB != 3000 {
				t.Errorf("below_usage_floor usage_mb = %d, want 3000", d.UsageMB)
			}
		})
	}
}

// B4 — cross-guest body vmid → 403, SetConfig not called.
func TestGuestMemory_CrossGuestRefused(t *testing.T) {
	f := stdFixture()
	h := memServer(t, f).Handler()
	w := do(t, h, "POST", "/guest/memory", "A", `{"vmid":9999,"memory_mb":10000}`)
	if w.Code != http.StatusForbidden {
		t.Fatalf("cross-guest = %d, want 403", w.Code)
	}
	if f.calls() != 0 {
		t.Errorf("SetConfig called on a cross-guest refusal (%d)", f.calls())
	}
}

// B5 — bounds are re-read FRESH per request: raising usage between the GET and the POST makes a
// previously-valid shrink target fall below the NEW floor (a stale UI can't smuggle an old floor).
func TestGuestMemory_FreshBoundsPerRequest(t *testing.T) {
	f := stdFixture() // usage 3000 → floor 3512
	h := memServer(t, f).Handler()
	// GET sees floor 3512; target 3600 would be a valid shrink under it.
	if d := decodeMem(t, do(t, h, "GET", "/guest/memory", "A", "").Body.Bytes()).Data; d.FloorMB != 3512 {
		t.Fatalf("initial floor = %d, want 3512", d.FloorMB)
	}
	// Usage climbs to 3600 MB → floor becomes 4112. The POST must read this FRESH.
	f.mu.Lock()
	f.usageBytes = 3600 * mib
	f.mu.Unlock()
	w := do(t, h, "POST", "/guest/memory", "A", `{"memory_mb":3700}`)
	if w.Code != http.StatusPreconditionFailed {
		t.Fatalf("post = %d (%s), want 412 (fresh floor 4112 > 3700)", w.Code, w.Body.String())
	}
	d := decodeMem(t, w.Body.Bytes()).Data
	if d.Code != "below_usage_floor" || d.FloorMB != 4112 {
		t.Errorf("fresh-bounds refusal = code %q floor %d, want below_usage_floor / 4112", d.Code, d.FloorMB)
	}
	if f.calls() != 0 {
		t.Errorf("SetConfig called (%d) despite fresh-floor refusal", f.calls())
	}
}

// target == current allocation → success no-op, no SetConfig.
func TestGuestMemory_UnchangedNoOp(t *testing.T) {
	f := stdFixture()
	h := memServer(t, f).Handler()
	w := do(t, h, "POST", "/guest/memory", "A", `{"memory_mb":8192}`)
	if w.Code != 200 {
		t.Fatalf("no-op = %d (%s), want 200", w.Code, w.Body.String())
	}
	d := decodeMem(t, w.Body.Bytes()).Data
	if !d.Unchanged || f.calls() != 0 {
		t.Errorf("no-op should not SetConfig: unchanged=%v calls=%d", d.Unchanged, f.calls())
	}
}

// Verify-after-apply: SetConfig "succeeds" but the maxmem never reflects the target → 502, no false
// success (a pending/reboot-required outcome is caught, never claimed as done).
func TestGuestMemory_ApplyNotReflected(t *testing.T) {
	f := stdFixture()
	f.applyReflect = false // SetConfig returns ok but the guest keeps its old maxmem
	h := memServer(t, f).Handler()
	w := do(t, h, "POST", "/guest/memory", "A", `{"memory_mb":10000}`)
	if w.Code != http.StatusBadGateway {
		t.Fatalf("unreflected apply = %d (%s), want 502", w.Code, w.Body.String())
	}
	if f.calls() != 1 {
		t.Errorf("SetConfig calls = %d, want 1 (it was attempted)", f.calls())
	}
}

// Not configured (nil Memory) → 503 on both routes.
func TestGuestMemory_NotConfigured(t *testing.T) {
	s := newTestServerS(t, &fakeGuests{}, &fakeBackups{}, &fakeStore{}, nil) // mem stays nil
	h := s.Handler()
	if w := do(t, h, "GET", "/guest/memory", "A", ""); w.Code != http.StatusServiceUnavailable {
		t.Errorf("GET nil-mem = %d, want 503", w.Code)
	}
	if w := do(t, h, "POST", "/guest/memory", "A", `{"memory_mb":9000}`); w.Code != http.StatusServiceUnavailable {
		t.Errorf("POST nil-mem = %d, want 503", w.Code)
	}
}