package agents

import (
	"context"
	"fmt"
	"log/slog"

	"g.fc.run/misc/byre/internal/api"
	"g.fc.run/misc/byre/internal/git"
)

func mergeInPrompt(target string) string {
	return fmt.Sprintf("Merge %[1]s into this branch: run `git merge --no-ff --no-commit %[1]s`. "+
		"Resolve any conflicts keeping both sides' intent; regenerate generated files instead of hand-merging them. "+
		"Check that the build and tests pass. Leave the merge uncommitted: byre concludes it when the turn ends.", target)
}

func (m *Manager) MergeIn(ctx context.Context, task api.Task, user api.User, target string) (api.AgentSession, error) {
	sessions, err := m.store.ListSessions(ctx, task.Id)
	if err != nil {
		return api.AgentSession{}, err
	}

	for _, sess := range sessions {
		if sess.State != api.AgentSessionStateCompleted {
			return m.Send(ctx, sess.Id, "byre", mergeInPrompt(target), "")
		}
	}

	return m.create(ctx, task, user, mergeInPrompt(target), "", "byre", nil)
}

func (m *Manager) Merge(ctx context.Context, task api.Task, project api.Project, user api.User) (api.AgentSession, error) {
	if user.GitName == "" || user.GitEmail == "" {
		return api.AgentSession{}, ErrNoGitIdentity
	}

	m.mu.Lock()
	m.merges[task.Id] = user.Login
	m.mu.Unlock()

	sess, err := m.MergeIn(ctx, task, user, project.DefaultBranch)
	if err != nil {
		m.mu.Lock()
		delete(m.merges, task.Id)
		m.mu.Unlock()
	}
	return sess, err
}

func (m *Manager) takeMerge(taskID string) (string, bool) {
	m.mu.Lock()
	defer m.mu.Unlock()
	login, ok := m.merges[taskID]
	delete(m.merges, taskID)
	return login, ok
}

func (m *Manager) finishMerge(l *live, login string) {
	ctx := context.Background()
	err := m.squashAndClose(ctx, l.taskID, login)
	if err == nil {
		return
	}

	slog.Error("finish merge", "task", l.taskID, "err", err)
	m.fileError(l, "The agent merged the default branch in, but squashing onto it failed: "+err.Error())
	err = m.Deliver(ctx, l.id)
	if err != nil {
		slog.Error("deliver inbox responses", "session", l.id, "err", err)
	}
}

func (m *Manager) squashAndClose(ctx context.Context, taskID, login string) error {
	task, err := m.store.GetTask(ctx, taskID)
	if err != nil {
		return err
	}
	project, err := m.store.GetProject(ctx, task.ProjectId)
	if err != nil {
		return err
	}
	user, err := m.store.GetUser(ctx, login)
	if err != nil {
		return err
	}

	commit, err := git.SquashMerge(project.RepoPath, task.WorktreePath, project.DefaultBranch, task.Title, []string{
		"GIT_AUTHOR_NAME=" + user.GitName,
		"GIT_AUTHOR_EMAIL=" + user.GitEmail,
		"GIT_COMMITTER_NAME=" + user.GitName,
		"GIT_COMMITTER_EMAIL=" + user.GitEmail,
	})
	if err != nil {
		return err
	}

	err = m.RemoveTask(ctx, task, project, login)
	if err != nil {
		return err
	}

	_, err = m.store.MergeTask(ctx, taskID, commit, login)
	return err
}

func (m *Manager) RemoveTask(ctx context.Context, task api.Task, project api.Project, actor string) error {
	err := m.StopTask(ctx, task.Id, actor)
	if err != nil {
		return err
	}
	return git.RemoveWorktree(project.RepoPath, task.WorktreePath, task.Branch)
}