package core

import (
	"errors"
	"testing"
)

func TestParseProposalState(t *testing.T) {
	tests := []struct {
		in string
		ok bool
	}{
		{"open", true},
		{"merged", true},
		{"rejected", true},

		// The states that were deliberately collapsed away. Accepting either
		// would resurrect a review conversation that has no second party.
		{"approved", false},
		{"changes-requested", false},
		{"closed", false},
		{"draft", false},

		{"", false},
		{"Open", false},
		{"OPEN", false},
		{"open ", false},
		{" open", false},
		{"открыт", false},
	}
	for _, tc := range tests {
		st, err := ParseProposalState(tc.in)
		if (err == nil) != tc.ok {
			t.Errorf("ParseProposalState(%q) = %q, %v, want ok=%v", tc.in, st, err, tc.ok)
		}
		if err != nil && !errors.Is(err, ErrInvalidState) {
			t.Errorf("ParseProposalState(%q) error %v is not ErrInvalidState", tc.in, err)
		}
	}
}

func TestProposalStatesIsExactlyThree(t *testing.T) {
	got := ProposalStates()
	if len(got) != 3 {
		t.Fatalf("ProposalStates() = %v, want exactly open/merged/rejected", got)
	}
	want := []ProposalState{StateOpen, StateMerged, StateRejected}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("ProposalStates() = %v, want %v", got, want)
		}
	}
}

func TestProposalTransitions(t *testing.T) {
	all := []ProposalState{StateOpen, StateMerged, StateRejected}

	// The whole table, explicitly: only the two edges out of `open` exist.
	want := map[ProposalState]map[ProposalState]bool{
		StateOpen:     {StateOpen: false, StateMerged: true, StateRejected: true},
		StateMerged:   {StateOpen: false, StateMerged: false, StateRejected: false},
		StateRejected: {StateOpen: false, StateMerged: false, StateRejected: false},
	}

	for _, from := range all {
		for _, to := range all {
			t.Run(string(from)+"->"+string(to), func(t *testing.T) {
				expect := want[from][to]
				if got := ValidTransition(from, to); got != expect {
					t.Fatalf("ValidTransition(%s, %s) = %v, want %v", from, to, got, expect)
				}
				err := from.CanTransitionTo(to)
				if (err == nil) != expect {
					t.Fatalf("%s.CanTransitionTo(%s) = %v, want ok=%v", from, to, err, expect)
				}
				if err != nil && !errors.Is(err, ErrInvalidTransition) {
					t.Fatalf("error %v is not ErrInvalidTransition", err)
				}
			})
		}
	}
}

func TestCanTransitionToRejectsUnknownStates(t *testing.T) {
	// An unparseable state is a different failure class from an illegal edge:
	// it means something wrote garbage into the proposal row.
	if err := ProposalState("approved").CanTransitionTo(StateMerged); !errors.Is(err, ErrInvalidState) {
		t.Fatalf("from=approved: %v, want ErrInvalidState", err)
	}
	if err := StateOpen.CanTransitionTo("approved"); !errors.Is(err, ErrInvalidState) {
		t.Fatalf("to=approved: %v, want ErrInvalidState", err)
	}
	if err := ProposalState("").CanTransitionTo(StateMerged); !errors.Is(err, ErrInvalidState) {
		t.Fatalf("from=empty: %v, want ErrInvalidState", err)
	}
}

func TestProposalStateTerminal(t *testing.T) {
	tests := []struct {
		in   ProposalState
		want bool
	}{
		{StateOpen, false},
		{StateMerged, true},
		{StateRejected, true},
		{"", false},
		{"approved", false},
	}
	for _, tc := range tests {
		if got := tc.in.Terminal(); got != tc.want {
			t.Errorf("%q.Terminal() = %v, want %v", tc.in, got, tc.want)
		}
	}
}

func TestParseApproval(t *testing.T) {
	tests := []struct {
		in string
		ok bool
	}{
		{"human", true},
		{"policy", true},

		{"", false},
		{"auto", false},
		{"Human", false},
		{"human ", false},
		{"approved", false},
	}
	for _, tc := range tests {
		a, err := ParseApproval(tc.in)
		if (err == nil) != tc.ok {
			t.Errorf("ParseApproval(%q) = %q, %v, want ok=%v", tc.in, a, err, tc.ok)
		}
		if err != nil && !errors.Is(err, ErrInvalidApproval) {
			t.Errorf("ParseApproval(%q) error %v is not ErrInvalidApproval", tc.in, err)
		}
	}
}

// A policy-merged document must be distinguishable from a human-approved one:
// collapsing the two would quietly launder unreviewed agent output as blessed.
func TestApprovalKindsAreDistinct(t *testing.T) {
	if ApprovalHuman == ApprovalPolicy {
		t.Fatal("human and policy approval must not be the same value")
	}
}