use crate::{
    app::{App, Message},
    source_navigation::{
        SymbolEvent,
        query::{Declaration, Disposition, Evidence, Identity, Membership, Position},
    },
    style,
};
use iced::{
    Element, Fill,
    widget::{button, column, container, scrollable, text, tooltip},
};

pub(super) fn panel(app: &App, current: bool) -> Element<'_, Message> {
    use crate::app::text_workspace::{DrawerTab, Event};
    use std::collections::BTreeSet;
    let state = &app.source_symbols;
    let visible = app.text_workspace.drawer() == Some(DrawerTab::References);
    let presentation = app.text_workspace.references();
    let mut content = column![].spacing(0).width(Fill);
    if visible && let Some(notice) = &state.notice {
        content = content.push(text(notice.clone()).size(12));
    }
    if visible && let Some(results) = &state.results {
        let stale = !current;
        let enabled = !stale && app.source_navigation_available();
        let files: BTreeSet<_> = results
            .definitions
            .iter()
            .map(|row| row.path.as_str())
            .chain(results.references.iter().map(|row| row.path.as_str()))
            .collect();
        let mut ordered: Vec<_> = files.iter().copied().collect();
        // Keep the query's captured origin first even after navigating elsewhere.
        if let Some(origin) = state
            .display_request
            .as_ref()
            .map(|request| request.path.as_str())
        {
            ordered.sort_by_key(|path| (*path != origin, *path));
        }
        for path in ordered {
            let collapsed = presentation.collapsed(path);
            let count = results
                .definitions
                .iter()
                .filter(|row| row.path == path)
                .count()
                + results
                    .references
                    .iter()
                    .filter(|row| row.path == path)
                    .count();
            let suffix = distinguishing_path(path, &files);
            content = content.push(
                button(
                    text(format!(
                        "{} {suffix} · {count}",
                        if collapsed { "▸" } else { "▾" }
                    ))
                    .size(12)
                    .wrapping(iced::widget::text::Wrapping::None),
                )
                .height(24)
                .width(Fill)
                .padding([2, 6])
                .style(style::nav)
                .on_press_maybe(app.source_navigation_available().then(|| {
                    Message::TextWorkspace(Event::ToggleFile {
                        stamp: results.stamp,
                        visit: app.text_workspace.drawer_visit(),
                        path: path.to_owned(),
                    })
                })),
            );
            if collapsed {
                continue;
            }
            for (index, definition) in results
                .definitions
                .iter()
                .enumerate()
                .filter(|(_, row)| row.path == path)
            {
                content = content.push(location_row(
                    declaration_title(&definition.declaration),
                    path,
                    definition.position,
                    provenance(
                        definition.membership,
                        definition.evidence,
                        definition.declaration.identity,
                        false,
                    ),
                    enabled.then(|| {
                        app.source_symbol_message(SymbolEvent::Choose {
                            stamp: results.stamp,
                            visit: app.text_workspace.drawer_visit(),
                            reference: false,
                            index,
                        })
                    }),
                ));
            }
            for (index, reference) in results
                .references
                .iter()
                .enumerate()
                .filter(|(_, row)| row.path == path)
            {
                let title = reference.context.as_ref().map_or_else(
                    || format!("@{} · lexical use", preview(&reference.alias, 48)),
                    |context| format!("use · {}", declaration_title(context)),
                );
                content = content.push(location_row(
                    title,
                    path,
                    reference.position,
                    provenance(
                        reference.membership,
                        reference.evidence,
                        reference
                            .context
                            .as_ref()
                            .map_or(Identity::Missing, |context| context.identity),
                        true,
                    ),
                    enabled.then(|| {
                        app.source_symbol_message(SymbolEvent::Choose {
                            stamp: results.stamp,
                            visit: app.text_workspace.drawer_visit(),
                            reference: true,
                            index,
                        })
                    }),
                ));
            }
            // Full path is readable by ordinary scrolling, independently of hover.
            content = content.push(
                container(
                    text(path.to_owned())
                        .font(iced::Font::MONOSPACE)
                        .size(12)
                        .wrapping(iced::widget::text::Wrapping::WordOrGlyph),
                )
                .padding([3, 8]),
            );
        }
        let scope = &results.scope;
        let explanation = match results.disposition {
            Disposition::NoSymbol => "Place the caret on a declaration alias or an @reference.",
            Disposition::NoDefinition => "No matching declaration in the loaded sources.",
            Disposition::Choices => {
                "Choose a declaration; draft and detached candidates need an explicit choice."
            }
            Disposition::Direct => "Definition in the current sources.",
            Disposition::LexicalReferences => {
                "Lexical uses of this alias; these do not establish a semantic target."
            }
        };
        content = content.push(text(explanation).size(12));
        if stale {
            content = content.push(
                text("Source changed. Run Definition or References again for current locations.")
                    .size(12),
            );
        }
        if results.total_definitions > 1 {
            content = content.push(
                text("Alias collision: uses are not attributed to a single declaration.").size(12),
            );
        }
        content = content
            .push(
                text(format!(
                    "{} · {} included / {} detached / {} unverified files · {} scope issues",
                    if scope.partial() {
                        "Partial include scope"
                    } else {
                        "Complete include scope"
                    },
                    scope.included_files,
                    scope.detached_files,
                    scope.unverified_files,
                    scope.issues.len()
                ))
                .size(12),
            )
            .push(
                text(if !scope.applied {
                    "Unapplied drafts"
                } else if scope.validated {
                    "Validated sources"
                } else {
                    "Draft sources"
                })
                .size(12),
            )
            .push(
                text(counts(
                    "Declarations",
                    results.definitions.len(),
                    results.total_definitions,
                    results.omitted_definitions,
                ))
                .size(12),
            )
            .push(
                text(counts(
                    "Lexical uses",
                    results.references.len(),
                    results.total_references,
                    results.omitted_references,
                ))
                .size(12),
            );
    }
    let identity = if visible {
        state
            .display_request
            .as_ref()
            .map(|request| (request.job, app.text_workspace.drawer_visit()))
    } else {
        None
    };
    let guarded = crate::diagnostic_input::Guard::new(identity, content);
    let mut body = scrollable(
        container(guarded)
            .width(Fill)
            .padding(iced::Padding::ZERO.right(14)),
    )
    .id(app.text_workspace.reference_scroll_id())
    .height(Fill)
    .width(Fill);
    if let Some(stamp) = presentation.stamp() {
        let visit = app.text_workspace.drawer_visit();
        body = body.on_scroll(move |viewport| {
            Message::TextWorkspace(Event::ReferenceScrolled {
                stamp,
                visit,
                y: viewport.absolute_offset().y,
            })
        });
    }
    body.into()
}

/// Shortest suffix that still distinguishes duplicate basenames and suffix paths.
fn distinguishing_path<'a>(path: &'a str, files: &std::collections::BTreeSet<&str>) -> &'a str {
    let starts = std::iter::once(0).chain(path.match_indices('/').map(|(index, _)| index + 1));
    for start in starts.collect::<Vec<_>>().into_iter().rev() {
        let candidate = &path[start..];
        if files
            .iter()
            .filter(|other| {
                **other == candidate
                    || other
                        .strip_suffix(candidate)
                        .is_some_and(|prefix| prefix.ends_with('/'))
            })
            .count()
            == 1
        {
            return candidate;
        }
    }
    path
}

fn counts(label: &str, shown: usize, total: usize, omitted: usize) -> String {
    format!("{label}: {total} total · {shown} shown · {omitted} omitted")
}

fn declaration_title(declaration: &Declaration) -> String {
    let name = declaration
        .name
        .as_ref()
        .map_or_else(String::new, |name| format!(" \"{}\"", preview(name, 48)));
    format!(
        "{}{} · @{}",
        preview(&declaration.kind, 24),
        name,
        preview(&declaration.alias, 48)
    )
}

fn provenance(
    membership: Membership,
    evidence: Evidence,
    identity: Identity,
    context: bool,
) -> String {
    let membership = match membership {
        Membership::Included => "Included",
        Membership::Detached => "Detached",
        Membership::Unverified => "Unverified",
    };
    let evidence = match evidence {
        Evidence::Validated => "Validated",
        Evidence::Draft => "Draft",
    };
    let collision = match identity {
        Identity::Collision { count } => format!(
            " · {}ID collision ({count})",
            if context { "Context " } else { "" },
        ),
        Identity::Missing | Identity::Unique(_) => String::new(),
    };
    format!("{membership} · {evidence}{collision}")
}

fn location_row(
    title: String,
    path: &str,
    position: Position,
    status: String,
    event: Option<Message>,
) -> Element<'static, Message> {
    let line = position.line.saturating_add(1);
    let column = position.byte_column.saturating_add(1);
    let full =
        format!("{path}:{line}:{column} · {title} · {status} (1-based line and UTF-8 byte column)");
    tooltip(
        button(
            container(
                text(format!("{line}:{column}  {title} · {status}"))
                    .size(12)
                    .wrapping(iced::widget::text::Wrapping::None),
            )
            .clip(true)
            .width(Fill),
        )
        .padding([3, 12])
        .height(28)
        .width(Fill)
        .style(style::nav)
        .on_press_maybe(event),
        text(full).size(12),
        tooltip::Position::Top,
    )
    .into()
}

/// Keep headings compact without copying the remainder of a long admitted value.
fn preview(value: &str, limit: usize) -> String {
    let mut chars = value.chars();
    let mut result: String = chars
        .by_ref()
        .take(limit)
        .map(|ch| if ch.is_whitespace() { ' ' } else { ch })
        .collect();
    if chars.next().is_some() {
        result.push('…');
    }
    result
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn suffixes_distinguish_nested_duplicate_basenames_without_changing_unicode() {
        let files = [
            "a/core.arcadia",
            "b/core.arcadia",
            "core.arcadia",
            "救援/actors.arcadia",
        ]
        .into_iter()
        .collect();
        assert_eq!(
            distinguishing_path("a/core.arcadia", &files),
            "a/core.arcadia"
        );
        assert_eq!(
            distinguishing_path("b/core.arcadia", &files),
            "b/core.arcadia"
        );
        assert_eq!(distinguishing_path("core.arcadia", &files), "core.arcadia");
        assert_eq!(
            distinguishing_path("救援/actors.arcadia", &files),
            "actors.arcadia"
        );
    }
}