use crate::task;
use crate::util;

use anyhow::Context as _;
use forgejo_api::structs::Issue;

pub async fn collect_tasks(ctx: &crate::Context) -> anyhow::Result<Vec<task::Task>> {
    let issues = list_all_issues(ctx).await?;

    let tasks = issues
        .into_iter()
        .map(|issue| {
            task_from_issue(&issue).with_context(|| {
                format!(
                    "Error while converting issue #{} to task",
                    issue.number.unwrap_or(-1)
                )
            })
        })
        .collect::<anyhow::Result<Vec<_>>>()?;

    Ok(tasks)
}

fn task_from_issue(issue: &Issue) -> anyhow::Result<task::Task> {
    Ok(task::Task {
        issue_number: issue.get_number()?,
        title: issue.get_title()?,
        state: task_state_from_issue(issue)?,
        recurring: task_recurring_from_issue_labels(issue)?,
    })
}

fn task_state_from_issue(issue: &Issue) -> anyhow::Result<task::State> {
    match issue.get_state()? {
        forgejo_api::structs::StateType::Open => Ok(task::State::Open {
            due: issue.due_date.map(util::time_to_jiff),
        }),
        forgejo_api::structs::StateType::Closed => Ok(task::State::Completed {
            date: util::time_to_jiff(issue
                .closed_at
                .context("Closed issue without a closed_at date")?),
        }),
    }
}

fn task_recurring_from_issue_labels(issue: &Issue) -> anyhow::Result<Option<task::Recurring>> {
    let labels = issue.get_label_names()?;
    let Some(recurring_label) = get_recurring_label(&labels)? else {
        return Ok(None)
    };

    let interval = match recurring_label {
        // Months
        "Every Month" => task::RecurringInterval::Months(1),
        "Every 2 Months" => task::RecurringInterval::Months(2),
        "Every 3 Months" => task::RecurringInterval::Months(3),
        "Every 4 Months" => task::RecurringInterval::Months(4),
        "Every 5 Months" => task::RecurringInterval::Months(5),
        "Every 6 Months" => task::RecurringInterval::Months(6),
        "Every 7 Months" => task::RecurringInterval::Months(7),
        "Every 8 Months" => task::RecurringInterval::Months(8),
        "Every 9 Months" => task::RecurringInterval::Months(9),
        "Every 10 Months" => task::RecurringInterval::Months(10),
        "Every 11 Months" => task::RecurringInterval::Months(11),
        "Every Year" => task::RecurringInterval::Months(12),
        // Weeks
        "Every Week" => task::RecurringInterval::Weeks(1),
        "Every 2 Weeks" => task::RecurringInterval::Weeks(2),
        "Every 3 Weeks" => task::RecurringInterval::Weeks(3),
        "Every 4 Weeks" => task::RecurringInterval::Weeks(4),
        "Every 5 Weeks" => task::RecurringInterval::Weeks(5),
        "Every 6 Weeks" => task::RecurringInterval::Weeks(6),
        "Every 7 Weeks" => task::RecurringInterval::Weeks(7),
        "Every 8 Weeks" => task::RecurringInterval::Weeks(8),
        "Every 9 Weeks" => task::RecurringInterval::Weeks(9),
        "Every 10 Weeks" => task::RecurringInterval::Weeks(10),
        // Days
        "Every Day" => task::RecurringInterval::Days(1),
        "Every 2 Days" => task::RecurringInterval::Days(2),
        "Every 3 Days" => task::RecurringInterval::Days(3),
        "Every 4 Days" => task::RecurringInterval::Days(4),
        "Every 5 Days" => task::RecurringInterval::Days(5),
        "Every 6 Days" => task::RecurringInterval::Days(6),
        // Fallback
        s => anyhow::bail!("Unknown recurring interval: {s:?}"),
    };

    Ok(Some(task::Recurring { interval }))
}

fn get_recurring_label(labels: &[String]) -> anyhow::Result<Option<&str>> {
    let mut recurring_labels_iter = labels
        .iter()
        .filter_map(|label| label.strip_prefix("Recurring/"));
    let Some(recurring_label) = recurring_labels_iter.next() else {
        // No recurring label means this is not a recurring task
        return Ok(None);
    };
    if recurring_labels_iter.next().is_some() {
        anyhow::bail!("More than one Recurring/ label found on issue");
    }
    Ok(Some(recurring_label))
}

async fn list_all_issues(ctx: &crate::Context) -> anyhow::Result<Vec<Issue>> {
    let issues = 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),
                // Only issues
                r#type: Some(forgejo_api::structs::IssueListIssuesQueryType::Issues),
                ..Default::default()
            },
        )
        .all()
        .await
        .with_context(|| format!("Failed fetching issue list"))?;

    Ok(issues)
}

trait IssueExt {
    fn get_number(&self) -> anyhow::Result<u32>;
    fn get_title(&self) -> anyhow::Result<String>;
    fn get_state(&self) -> anyhow::Result<forgejo_api::structs::StateType>;
    fn get_label_names(&self) -> anyhow::Result<Vec<String>>;
}

impl IssueExt for Issue {
    fn get_number(&self) -> anyhow::Result<u32> {
        Ok(self
            .number
            .context("Missing issue number")?
            .try_into()
            .context("Failed converting issue number to u32")?)
    }

    fn get_title(&self) -> anyhow::Result<String> {
        Ok(self.title.as_ref().context("Missing issue title")?.clone())
    }

    fn get_state(&self) -> anyhow::Result<forgejo_api::structs::StateType> {
        Ok(self.state.context("Issue has no state")?)
    }

    fn get_label_names(&self) -> anyhow::Result<Vec<std::string::String>> {
        let labels = self.labels.as_ref().context("Issue without labels list")?;
        let label_names = labels
            .into_iter()
            .map(|label| label.name.as_ref().context("Label without name").cloned())
            .collect::<anyhow::Result<Vec<_>>>()?;
        Ok(label_names)
    }
}