use anyhow::Context as _;

/// Read all issues to generate the full techtree
pub async fn collect_tree(ctx: &crate::Context) -> anyhow::Result<crate::tree::Tree> {
    let mut issues = vec![];
    for page in 1.. {
        let new = ctx
            .forgejo
            .issue_list_issues(
                &ctx.owner,
                &ctx.repo,
                forgejo_api::structs::IssueListIssuesQuery {
                    // We also want the closed issues
                    state: Some(forgejo_api::structs::IssueListIssuesQueryState::All),
                    // We cannot turn off pagination entirely, but let's set the limit as high as
                    // Forgejo lets us.
                    limit: Some(10000),
                    page: Some(page),
                    // Only issues
                    r#type: Some(forgejo_api::structs::IssueListIssuesQueryType::Issues),
                    ..Default::default()
                },
            )
            .await
            .with_context(|| format!("Failed fetching page {page} of the issue list"))?;

        if new.len() == 0 {
            break;
        }

        issues.extend(new);
    }

    let mut tree = crate::tree::Tree::new();
    let mut issue_numbers = Vec::new();

    for issue in issues.iter() {
        let element = match element_from_issue(issue) {
            Ok(el) => el,
            Err(e) => {
                let maybe_number = issue
                    .number
                    .map(|n| n.to_string())
                    .unwrap_or("<unknown>".to_owned());
                log::warn!("Failed processing issue #{maybe_number}: {e:?}");
                continue;
            }
        };

        issue_numbers.push(element.issue_number);
        tree.add_element(element);
    }

    for issue in issue_numbers.into_iter() {
        let dependencies = ctx
            .forgejo
            .issue_list_issue_dependencies(
                &ctx.owner,
                &ctx.repo,
                // Why the hell is the issue number a string here?
                &issue.to_string(),
                forgejo_api::structs::IssueListIssueDependenciesQuery {
                    limit: Some(10000),
                    ..Default::default()
                },
            )
            .await
            .with_context(|| format!("Failed to fetch issue dependencies for #{issue}",))?;

        for dep in dependencies {
            // Check that the dependency is actually an issue in the techtree and not external
            let dep_repo = dep
                .repository
                .context("Dependency issue without repository info")?;
            if dep_repo.owner.as_ref() != Some(&ctx.owner)
                || dep_repo.name.as_ref() != Some(&ctx.repo)
            {
                log::warn!(
                    "Issue #{issue} depends on external {}#{}, ignoring.",
                    dep_repo.full_name.as_deref().unwrap_or("unknown?"),
                    dep.number.unwrap_or(9999)
                );
                continue;
            }

            let dep_number = dep.number.context("Missing issue number in dependency")?;
            if !tree.find_element_by_issue_number(dep_number).is_some() {
                log::warn!("Found dependency from #{issue} on non-tracked issue #{dep_number}!");
            } else {
                tree.add_dependency_by_issue_number(issue, dep_number);
            }
        }
    }

    Ok(tree)
}

fn element_from_issue(issue: &forgejo_api::structs::Issue) -> anyhow::Result<crate::tree::Element> {
    let issue_number = issue.number.context("Missing issue number")?;
    let description = issue
        .title
        .as_deref()
        .context("Issue is missing a title")?
        .to_owned();

    let labels = issue
        .labels
        .as_ref()
        .context("Issue does not have any labels")?;

    let ty_labels: Vec<_> = labels
        .iter()
        .filter_map(|l| l.name.as_deref())
        .filter(|l| l.starts_with("Type/"))
        .collect();

    if ty_labels.len() == 0 {
        anyhow::bail!("Issue #{issue_number} has no type label!");
    }
    if ty_labels.len() > 1 {
        anyhow::bail!("Issue #{issue_number} has more than one type label!");
    }

    let ty = ty_labels
        .first()
        .expect("TODO")
        .strip_prefix("Type/")
        .expect("TODO")
        .to_owned();

    let has_completed_label = labels
        .iter()
        .any(|l| l.name.as_deref() == Some("Completed"));

    let status = match issue.state.context("Missing issue state")? {
        forgejo_api::structs::StateType::Open => {
            if has_completed_label {
                crate::tree::ElementStatus::Completed
            } else if issue.assignee.is_some()
                || issue
                    .assignees
                    .as_ref()
                    .map(|v| v.len() > 0)
                    .unwrap_or(false)
            {
                crate::tree::ElementStatus::Assigned
            } else {
                crate::tree::ElementStatus::Missing
            }
        }
        forgejo_api::structs::StateType::Closed => anyhow::bail!("Ignoring closed issue!"),
    };

    Ok(crate::tree::Element {
        issue_number,
        description,
        ty,
        status,
    })
}