package service

import (
	"bytes"
	"context"
	"testing"
)

// TestProposalDiffReturnsChangedDocuments proves ProposalDiff returns exactly
// the documents a proposal changes — a modified one with its base and proposed
// content, and an added one marked new — and not the documents it leaves alone.
func TestProposalDiffReturnsChangedDocuments(t *testing.T) {
	svc, _ := newTestService(t)
	ctx := context.Background()
	sp, err := svc.CreateSpace(ctx, fxSpace)
	if err != nil {
		t.Fatalf("CreateSpace: %v", err)
	}
	// The approved head carries two documents; the proposal edits one, adds a
	// third, and leaves the second untouched.
	commitFiles(t, sp, sp.ApprovedBranch(), 1, map[string][]byte{
		"specs/a.md":    mdDoc("S-1", "A", "original body"),
		"specs/keep.md": mdDoc("S-2", "Keep", "unchanged body"),
	})
	base, err := sp.Repo.ApprovedHead(ctx)
	if err != nil {
		t.Fatalf("ApprovedHead: %v", err)
	}
	res, err := svc.Propose(ctx, ProposeRequest{
		Space:     fxSpace,
		Principal: agentPrincipal(),
		Title:     "edit and add",
		IfMatch:   base.String(),
		Message:   "two changes",
		Writes: []DocumentWrite{
			{Path: "specs/a.md", Content: mdDoc("S-1", "A", "revised body")},
			{Path: "specs/new.md", Content: mdDoc("S-3", "New", "brand new body")},
		},
	})
	if err != nil {
		t.Fatalf("Propose: %v", err)
	}

	docs, err := svc.ProposalDiff(ctx, res.Proposal)
	if err != nil {
		t.Fatalf("ProposalDiff: %v", err)
	}
	byPath := make(map[string]ProposalDoc, len(docs))
	for _, d := range docs {
		byPath[d.Path] = d
	}
	if _, ok := byPath["specs/keep.md"]; ok {
		t.Errorf("ProposalDiff returned the untouched specs/keep.md")
	}

	edited, ok := byPath["specs/a.md"]
	if !ok {
		t.Fatalf("ProposalDiff missing the edited document")
	}
	if edited.New {
		t.Errorf("specs/a.md marked new, want an edit")
	}
	if !bytes.Contains(edited.Base, []byte("original body")) {
		t.Errorf("edited doc base = %q, want the approved content", edited.Base)
	}
	if !bytes.Contains(edited.Proposed, []byte("revised body")) {
		t.Errorf("edited doc proposed = %q, want the proposal content", edited.Proposed)
	}

	added, ok := byPath["specs/new.md"]
	if !ok {
		t.Fatalf("ProposalDiff missing the added document")
	}
	if !added.New || added.Base != nil {
		t.Errorf("added doc = %+v, want New with a nil base", added)
	}
}