package task

import (
	"errors"
	"testing"
)

type fakeLookup struct {
	tasks map[string]*Task
}

func newFakeLookup() *fakeLookup {
	return &fakeLookup{tasks: make(map[string]*Task)}
}

func (f *fakeLookup) GetTask(id string) (*Task, error) {
	t, ok := f.tasks[id]
	if !ok {
		return nil, errors.New("not found")
	}
	return t, nil
}

func (f *fakeLookup) ListDependents(taskID string) ([]*Task, error) {
	var out []*Task
	for _, t := range f.tasks {
		for _, d := range t.DependsOn {
			if d == taskID {
				out = append(out, t)
				break
			}
		}
	}
	return out, nil
}

func TestCurrentAttempt_NoFixAttempt_ReturnsAnchorItself(t *testing.T) {
	lookup := newFakeLookup()
	lookup.tasks["a"] = &Task{ID: "a"}

	got, err := CurrentAttempt(lookup, "a")
	if err != nil {
		t.Fatalf("CurrentAttempt: %v", err)
	}
	if got.ID != "a" {
		t.Errorf("got %q, want a", got.ID)
	}
}

func TestCurrentAttempt_OneFixAttempt_ResolvesToIt(t *testing.T) {
	lookup := newFakeLookup()
	lookup.tasks["a"] = &Task{ID: "a", ParentTaskID: "parent-1"}
	lookup.tasks["a-fix1"] = &Task{ID: "a-fix1", ParentTaskID: "parent-1", DependsOn: []string{"a"}}

	got, err := CurrentAttempt(lookup, "a")
	if err != nil {
		t.Fatalf("CurrentAttempt: %v", err)
	}
	if got.ID != "a-fix1" {
		t.Errorf("got %q, want a-fix1", got.ID)
	}
}

func TestCurrentAttempt_ChainOfFixAttempts_ResolvesToTip(t *testing.T) {
	lookup := newFakeLookup()
	lookup.tasks["a"] = &Task{ID: "a", ParentTaskID: "parent-1"}
	lookup.tasks["a-fix1"] = &Task{ID: "a-fix1", ParentTaskID: "parent-1", DependsOn: []string{"a"}}
	lookup.tasks["a-fix2"] = &Task{ID: "a-fix2", ParentTaskID: "parent-1", DependsOn: []string{"a-fix1"}}

	got, err := CurrentAttempt(lookup, "a")
	if err != nil {
		t.Fatalf("CurrentAttempt: %v", err)
	}
	if got.ID != "a-fix2" {
		t.Errorf("got %q, want a-fix2 (tip of the chain)", got.ID)
	}

	// Resolving from an intermediate link in the chain also lands on the tip.
	got, err = CurrentAttempt(lookup, "a-fix1")
	if err != nil {
		t.Fatalf("CurrentAttempt: %v", err)
	}
	if got.ID != "a-fix2" {
		t.Errorf("resolving from a-fix1: got %q, want a-fix2", got.ID)
	}
}

// TestCurrentAttempt_DependentWithDifferentParent_NotTreatedAsFixAttempt
// proves a task that depends on "a" but has a DIFFERENT ParentTaskID (e.g.
// an unrelated Evaluator task depending on a Builder for scheduling reasons)
// must not be mistaken for a's fix attempt.
func TestCurrentAttempt_DependentWithDifferentParent_NotTreatedAsFixAttempt(t *testing.T) {
	lookup := newFakeLookup()
	lookup.tasks["a"] = &Task{ID: "a", ParentTaskID: "parent-1"}
	lookup.tasks["unrelated"] = &Task{ID: "unrelated", ParentTaskID: "", DependsOn: []string{"a"}}

	got, err := CurrentAttempt(lookup, "a")
	if err != nil {
		t.Fatalf("CurrentAttempt: %v", err)
	}
	if got.ID != "a" {
		t.Errorf("got %q, want a (unrelated dependent must not be treated as a fix attempt)", got.ID)
	}
}

// TestCurrentAttempt_DependentWithMultipleDependsOn_NotTreatedAsFixAttempt
// proves a fix attempt has exactly one DependsOn entry (the task it
// supersedes); a task depending on "a" among several dependencies (e.g. an
// Arbitration task depending on all 4 Evaluators) must not be mistaken for
// a's fix attempt.
func TestCurrentAttempt_DependentWithMultipleDependsOn_NotTreatedAsFixAttempt(t *testing.T) {
	lookup := newFakeLookup()
	lookup.tasks["a"] = &Task{ID: "a", ParentTaskID: "parent-1"}
	lookup.tasks["multi-dep"] = &Task{ID: "multi-dep", ParentTaskID: "parent-1", DependsOn: []string{"a", "b"}}

	got, err := CurrentAttempt(lookup, "a")
	if err != nil {
		t.Fatalf("CurrentAttempt: %v", err)
	}
	if got.ID != "a" {
		t.Errorf("got %q, want a", got.ID)
	}
}

func TestCurrentAttempt_UnknownAnchor_ReturnsError(t *testing.T) {
	lookup := newFakeLookup()
	if _, err := CurrentAttempt(lookup, "does-not-exist"); err == nil {
		t.Error("expected an error for an unknown anchor ID")
	}
}