use std::collections::HashMap;

use chrono::{DateTime, Datelike, Utc};
use gloo_net::http::Request;
use serde::Deserialize;
use wasm_bindgen_futures::spawn_local;
use yew::prelude::*;

use crate::dequote;
use crate::pages::ticket::{ActiveUser, Ticket};

/// A partial representation of a ticket, containing only the fields necessary for statistical analysis.
///
/// This struct is used to efficiently retrieve and process ticket data for diagnostics
/// without fetching the full ticket details.
///
/// # Fields
/// - `date`: The creation date and time of the ticket in UTC.
/// - `room`: The room number associated with the ticket.
#[derive(Debug, Deserialize, Clone, PartialEq)]
struct TicketPartial {
    date: DateTime<Utc>,
    room: i16,
    user_id: i16,
}

/// A partial representation of a user, containing only the fields necessary for statistical analysis.
///
/// This struct is used to efficiently retrieve and process user data for diagnostics
/// without fetching the full user details.
///
/// # Fields
/// - `id`: The unique identifier of the user.
/// - `first_name`: The first name of the user.
/// - `last_name`: The last name of the user.
#[derive(Debug, Deserialize, Clone, PartialEq)]
struct UserPartial {
    id: i16,
    first_name: String,
    last_name: String,
}

/// Properties for components that display room-wise ticket totals.
///
/// This struct passes a list of partial ticket data to a component responsible
/// for calculating and visualizing ticket distribution per room.
///
/// # Fields
/// - `tickets`: A vector of [`TicketPartial`] containing ticket data relevant for room totals.
#[derive(Properties, PartialEq)]
struct RoomTotalsProps {
    tickets: Vec<TicketPartial>,
}

/// Properties for components that display user-wise ticket totals.
///
/// This struct passes a list of partial user data and partial ticket data to a component
/// responsible for calculating and visualizing ticket distribution per user.
///
/// # Fields
/// - `users`: A vector of [`UserPartial`] containing user data relevant for user totals.
/// - `tickets`: A vector of [`TicketPartial`] containing ticket data relevant for user totals.
#[derive(Properties, PartialEq)]
struct UserTotalProps {
    users: Vec<UserPartial>,
    tickets: Vec<TicketPartial>,
}

/// Converts a `chrono::DateTime<Utc>` object's weekday to a 0-indexed integer.
///
/// This function maps `chrono::Weekday` values (where Monday is 1, Sunday is 7)
/// to a 0-indexed system (Monday = 0, Sunday = 6).
///
/// # Arguments
/// - `dt`: A reference to a `DateTime<Utc>` object.
///
/// # Returns
/// A `usize` representing the weekday index (0 for Monday, ..., 6 for Sunday).
fn weekday_index(dt: &DateTime<Utc>) -> usize {
    // chrono::Weekday: Mon = 1 ... Sun = 7
    match dt.weekday() {
        chrono::Weekday::Mon => 0,
        chrono::Weekday::Tue => 1,
        chrono::Weekday::Wed => 2,
        chrono::Weekday::Thu => 3,
        chrono::Weekday::Fri => 4,
        chrono::Weekday::Sat => 5,
        chrono::Weekday::Sun => 6,
    }
}

/// Counts the number of tickets submitted on each day of the week.
///
/// This function takes a slice of `TicketPartial` and returns an array where each
/// element corresponds to a day of the week (Monday=0, Sunday=6) and contains
/// the total count of tickets submitted on that day.
///
/// # Arguments
/// - `tickets`: A slice of [`TicketPartial`] items to count.
///
/// # Returns
/// An array `[usize; 7]` with ticket counts for each weekday.
fn count_by_weekday(tickets: &[TicketPartial]) -> [usize; 7] {
    let mut counts = [0usize; 7];
    for t in tickets {
        counts[weekday_index(&t.date)] += 1;
    }
    counts
}

/// Calculates the occurrences of each weekday within the date range covered by the tickets.
///
/// This function determines the minimum and maximum dates from the provided [`TicketPartial`]
/// slice and then counts how many times each weekday occurs within that inclusive date range.
/// This is useful for normalizing ticket counts against the number of available days for each weekday.
///
/// # Arguments
/// - `partials`: A slice of [`TicketPartial`] items defining the date range.
///
/// # Returns
/// An array `[usize; 7]` where each element represents the number of times a
/// specific weekday (Monday=0, ..., Sunday=6) appears in the date range.
fn day_counts(partials: &[TicketPartial]) -> [usize; 7] {
    if partials.is_empty() {
        return [0usize; 7];
    }

    let mut min = partials[0].date.date_naive();
    let mut max = min;
    for d in partials.iter().skip(1) {
        let dt = d.date.date_naive();
        if dt < min {
            min = dt
        }
        if dt > max {
            max = dt
        }
    }

    let total_days = (max - min).num_days() + 1;
    if total_days <= 0 {
        return [0usize; 7];
    }

    let mut occ = [0usize; 7];
    let mut current = min;
    for _ in 0..total_days {
        let wd = current.weekday();
        let idx = match wd {
            chrono::Weekday::Mon => 0,
            chrono::Weekday::Tue => 1,
            chrono::Weekday::Wed => 2,
            chrono::Weekday::Thu => 3,
            chrono::Weekday::Fri => 4,
            chrono::Weekday::Sat => 5,
            chrono::Weekday::Sun => 6,
        };
        occ[idx] += 1;
        current += chrono::Duration::days(1);
    }

    occ
}

/// Converts a numerical room representation back into a human-readable string format.
///
/// This function is the inverse of the room parsing logic in
/// [`SubmitTicket`](`crate::pages::ticket::SubmitTicket`) component.
/// It converts negative numbers back to "K" prefixed rooms, numbers >= 1000 back to "D" prefixed rooms,
/// and other numbers to their string representation.
///
/// # Arguments
/// - `r`: An `i16` representing the internal numerical representation of a room.
///
/// # Returns
/// A `String` containing the formatted room number (e.g., "K1", "D1", "101").
fn parse_room(r: i16) -> String {
    if r < 0 {
        format!("K{}", r.abs())
    } else if r > 1000 {
        format!("D{}", r - 1000)
    } else {
        r.to_string()
    }
}

/// The main diagnostics dashboard component.
///
/// This component serves as a container for various statistical and diagnostic
/// views related to the application's tickets.
///
/// # Components Rendered
/// - [`TicketCount`]: Displays the count of open tickets.
/// - [`SubmitStats`]: Displays statistics related to ticket submissions (e.g., by weekday, by room).
///
/// # Example
/// ```rust
/// html! {
///     <Diagnostics />
/// }
/// ```
#[component(Diagnostics)]
pub fn diagnostics_component() -> Html {
    html! {
        <div>
            <TicketCount/>
            <SubmitStats/>
        </div>
    }
}

/// A component that displays the count of currently open (ToDo or InProgress) tickets.
///
/// This component fetches all tickets and the current user's details. It then filters
/// the tickets to count only those that are "ToDo" or "InProgress" and are either
/// created by the current user (for non-admins) or all tickets (for admins).
///
/// # State
/// Uses `use_state` hooks to manage:
/// - `tickets`: A vector of `Ticket` structs for all fetched tickets.
/// - `error`: Any error message from API calls.
/// - `loading`: A boolean indicating if data is being fetched.
/// - `user`: The `ActiveUser` details for conditional filtering.
///
/// # Functionality
/// - Fetches all tickets from `/api/tickets`.
/// - Fetches current user details from `/api/users/current`.
/// - Filters tickets by status ("ToDo" or "InProgress") and user ID (if not admin).
/// - Displays the count of matching tickets.
///
/// # Example
/// ```rust
/// html! {
///     <TicketCount />
/// }
/// ```
#[component(TicketCount)]
pub fn ticket_count_component() -> Html {
    let tickets = use_state(Vec::<Ticket>::new);
    let error = use_state(|| None::<String>);
    let loading = use_state(|| false);
    let user = use_state(|| ActiveUser {
        id: None,
        is_admin: false,
    });

    {
        let tickets = tickets.clone();
        let error = error.clone();
        let loading = loading.clone();

        use_effect_with((), move |_| {
            loading.set(true);
            spawn_local(async move {
                let url = "/api/tickets".to_string();
                match Request::get(&url).send().await {
                    Ok(response) if response.status() == 200 => {
                        match response.json::<Vec<Ticket>>().await {
                            Ok(t) => tickets.set(t),
                            Err(e) => error.set(Some(format!("parse error: {}", e))),
                        }
                    }
                    Ok(response) => {
                        if let Ok(text) = response.text().await {
                            error.set(Some(text));
                        } else {
                            error.set(Some(format!("status {}", response.status())));
                        }
                    }
                    Err(err) => error.set(Some(format!("Network error: {}", err))),
                }
                loading.set(false);
            });
            || ()
        });
    }

    {
        let user = user.clone();
        use_effect_with((), move |_| {
            let user = user.clone();
            spawn_local(async move {
                if let Ok(response) = Request::get("/api/users/current")
                    .credentials(web_sys::RequestCredentials::Include)
                    .send()
                    .await
                    && response.status() == 200
                    && let Ok(json) = response.json::<serde_json::Value>().await
                {
                    let id = json
                        .get("data")
                        .and_then(|d| d.get("id"))
                        .and_then(|v| v.as_i64())
                        .and_then(|n| i16::try_from(n).ok());
                    let is_admin = json
                        .get("data")
                        .and_then(|d| d.get("is_admin"))
                        .and_then(|v| v.as_bool())
                        .unwrap_or(false);
                    user.set(ActiveUser { id, is_admin });
                }
            });
            || ()
        });
    }

    if *loading {
        html! {<p>{ "Lade..." }</p>}
    } else if let Some(e) = &*error {
        html! { <p>{ format!("Fehler: {}", e) }</p> }
    } else {
        let status_conditions = |t: &Ticket| t.status == "ToDo" || t.status == "InProgress";
        let count = tickets
            .iter()
            .filter(|t| status_conditions(t) && (user.is_admin || (user.id == Some(t.user_id))))
            .count();
        html! {
            <div class="open-tickets">
                <h2 class="left">{ "Offene Tickets" }</h2>
                <h4 class="ticket_count center">{ count }</h4>
            </div>
        }
    }
}

/// A component that displays various statistics about ticket submissions.
///
/// This component fetches all tickets (in a partial format for efficiency)
/// and calculates statistics such as tickets per weekday and tickets per room.
/// It renders these statistics visually using simple bar charts.
///
/// # State
/// Uses `use_state` hooks to manage:
/// - `tickets`: A vector of [`TicketPartial`] for statistical analysis.
/// - `error`: Any error message from API calls.
/// - `loading`: A boolean indicating if data is being fetched.
///
/// # Functionality
/// - Fetches all tickets (as [`TicketPartial`]) from `/api/tickets`.
/// - Calculates:
///   - `counts`: Number of tickets submitted on each weekday.
///   - `occ`: Number of occurrences of each weekday in the ticket date range.
///   - `avg`: Average number of tickets per day for each weekday, normalized by `occ`.
/// - Renders a bar chart for average tickets per weekday.
/// - Renders a [`RoomTotalTickets`] component to display tickets per room.
///
/// # Example
/// ```rust
/// html! {
///     <SubmitStats />
/// }
/// ```
#[component(SubmitStats)]
pub fn submit_stats_component() -> Html {
    let tickets = use_state(Vec::<TicketPartial>::new);
    let users = use_state(Vec::<UserPartial>::new);
    let error = use_state(|| None::<String>);
    let loading = use_state(|| false);

    {
        let tickets = tickets.clone();
        let users = users.clone();
        let error = error.clone();
        let loading = loading.clone();

        use_effect_with((), move |_| {
            loading.set(true);
            spawn_local(async move {
                let url = "/api/tickets".to_string();
                match Request::get(&url).send().await {
                    Ok(response) if response.status() == 200 => {
                        match response.json::<Vec<TicketPartial>>().await {
                            Ok(t) => tickets.set(t),
                            Err(e) => error.set(Some(format!("parse error: {}", e))),
                        }
                    }
                    Ok(response) => {
                        if let Ok(text) = response.text().await {
                            error.set(Some(text));
                        } else {
                            error.set(Some(format!("status {}", response.status())));
                        }
                    }
                    Err(err) => error.set(Some(format!("Network error: {}", err))),
                }

                match Request::get("/api/users").send().await {
                    Ok(response) if response.status() == 200 => {
                        match response.json::<Vec<UserPartial>>().await {
                            Ok(u) => users.set(u),
                            Err(e) => error.set(Some(format!("users parse error: {}", e))),
                        }
                    }
                    Ok(response) => {
                        if let Ok(text) = response.text().await {
                            error.set(Some(text));
                        } else {
                            error.set(Some(format!("users status {}", response.status())));
                        }
                    }
                    Err(err) => error.set(Some(format!("users network error: {}", err))),
                }

                loading.set(false);
            });
            || ()
        });
    }

    let counts = count_by_weekday(&tickets);
    let occ = day_counts(&tickets);

    let mut avg = [0.0f64; 7];
    for i in 0..7 {
        if occ[i] > 0 {
            avg[i] = counts[i] as f64 / occ[i] as f64;
        } else {
            avg[i] = 0.0;
        }
    }

    let weekdays = ["Mo", "Di", "Mi", "Do", "Fr", "Sa", "So"];
    let (max_idx, _max_val) = counts
        .iter()
        .enumerate()
        .max_by(|a, b| a.1.partial_cmp(b.1).unwrap())
        .map(|(i, _)| (i, ()))
        .unwrap_or((0, ()));

    html! {
        <div class="diagnostics-section">
            if *loading {
                <p>{ "Lade..." }</p>
            }
            if let Some(e) = &*error {
                <p class="alert error">{ e.clone() }</p>
            }
            <h3>{ "Tickets pro Wochentag" }</h3>
            <div class="weekday-chart">
                <div class="weekday-bars">
                    { for (0..7).map(|i| {
                        let is_max = i == max_idx;
                        let max_value = counts.iter().cloned().max().unwrap_or(1).max(1);
                        let bar_height_percent = if max_value > 0 { (avg[i] / max_value as f64) * 100.0 } else { 0.0 };
                        let bar_height_px = (bar_height_percent * 200.0 / 100.0) as i32;
                        html! {
                            <div class="weekday-bar">
                                <div class={format!("bar{}", if is_max { " max" } else { "" })} style={format!("height: {}px;", bar_height_px)}>
                                </div>
                            </div>
                        }
                    })}
                </div>
                <div class="weekday-labels">
                    { for (0..7).map(|i| {
                        html! {
                            <div class="label-item">
                                <div class="day">{ weekdays[i] }</div>
                                <div class="value">{ format!("{:.1}", avg[i]) }</div>
                            </div>
                        }
                    })}
                </div>
            </div>
            <div class="diagnostics-row">
                <div class="diagnostics-column">
                    <h3>{ "Tickets pro Raum" }</h3>
                    <RoomTotalTickets tickets={(*tickets).clone()}/>
                </div>
                <div class="diagnostics-column">
                    <h3>{ "Tickets pro Benutzer" }</h3>
                    <UserTotal users={(*users).clone()} tickets={(*tickets).clone()}/>
                </div>
            </div>
        </div>
    }
}

/// A component that displays the total number of tickets per room.
///
/// This component takes a list of [`TicketPartial`] items and calculates the
/// total number of tickets for each room. It then displays these totals
/// in a sorted list with a bar chart visualization.
///
/// # Props
/// - `tickets`: A `Vec<TicketPartial>` containing the partial ticket data for analysis.
///
/// # Functionality
/// - **Calculates Totals**: Aggregates ticket counts for each unique room.
/// - **Sorts Results**: Displays rooms sorted by ticket count in descending order.
/// - **Visualizes Data**: Renders a bar chart where the width of each bar is
///   proportional to the ticket count for that room, relative to the room with the maximum tickets.
/// - **Room Formatting**: Uses the [`parse_room`] function to display room numbers
///   in a human-readable format.
///
/// # Example
/// ```rust
/// html! {
///     <RoomTotalTickets tickets={my_ticket_partials} />
/// }
/// ```
#[component(RoomTotalTickets)]
fn room_total_component(props: &RoomTotalsProps) -> Html {
    let mut totals: HashMap<i16, usize> = HashMap::new();
    for t in &props.tickets {
        *totals.entry(t.room).or_insert(0) += 1;
    }

    let mut totals_vec: Vec<(i16, usize)> = totals.into_iter().collect();
    totals_vec.sort_by(|a, b| b.1.cmp(&a.1));

    let max_count = totals_vec.iter().map(|(_, c)| *c).max().unwrap_or(1).max(1);

    html! {
        <div class="diagnostics-section">
            <div class="chart">
                { for totals_vec.into_iter().map(|(room, count)| {
                    let label = parse_room(room);
                    let bar_width_percent = (count as f64 / max_count as f64) * 100.0;
                    html! {
                        <div class="bar-item">
                            <div class="diagnostics-header">
                                <span class="diagnostics-label">{ label }</span>
                                <span class="diagnostics-count">{ count }</span>
                            </div>
                            <div class="bar-container">
                                <div class="bar" style={format!("width: {}%;", bar_width_percent)}>
                                </div>
                            </div>
                        </div>
                    }
                }) }
            </div>
        </div>
    }
}

/// A component that displays the total number of tickets per user.
///
/// This component takes lists of [`UserPartial`] and [`TicketPartial`] items to calculate
/// and display the total number of tickets submitted by each user.
/// The results are presented in a sorted list with a bar chart visualization.
///
/// # Props
/// - `users`: A `Vec<UserPartial>` containing partial user data.
/// - `tickets`: A `Vec<TicketPartial>` containing partial ticket data for analysis.
///
/// # Functionality
/// - **Maps User Names**: Creates a map from user IDs to their first and last names for display.
/// - **Calculates Totals**: Aggregates ticket counts for each user.
/// - **Sorts Results**: Displays users sorted by their ticket count in descending order.
/// - **Visualizes Data**: Renders a bar chart where the width of each bar is proportional
///   to the ticket count for that user, relative to the user with the maximum tickets.
/// - **Name Formatting**: Uses the [`dequote!`] macro to clean up user names before display.
///
/// # Example
/// ```rust
/// html! {
///     <UserTotal users={my_user_partials} tickets={my_ticket_partials} />
/// }
/// ```
#[component(UserTotal)]
fn user_total_component(props: &UserTotalProps) -> Html {
    let name_map: HashMap<i16, (String, String)> = props
        .users
        .iter()
        .map(|u| (u.id, (u.first_name.clone(), u.last_name.clone())))
        .collect();

    let mut counts: HashMap<i16, usize> = HashMap::new();
    for t in &props.tickets {
        *counts.entry(t.user_id).or_insert(0) += 1;
    }

    let mut totals_vec: Vec<(i16, String, String, usize)> = name_map
        .into_iter()
        .map(|(id, (fname, lname))| {
            let c = counts.get(&id).cloned().unwrap_or(0);
            (id, fname, lname, c)
        })
        .collect();

    totals_vec.sort_by(|a, b| b.3.cmp(&a.3));

    let max_count = totals_vec
        .iter()
        .map(|(_, _, _, c)| *c)
        .max()
        .unwrap_or(1)
        .max(1);

    html! {
        <div class="diagnostics-section">
            <div class="chart">
                { for totals_vec.into_iter().map(|(_id, fname, lname, count)| {
                    let label = format!("{} {}", dequote!(fname), dequote!(lname));
                    let bar_width_percent = (count as f64 / max_count as f64) * 100.0;
                    html! {
                        <div class="bar-item">
                            <div class="diagnostics-header">
                                <span class="diagnostics-label">{ label }</span>
                                <span class="diagnostics-count">{ count }</span>
                            </div>
                            <div class="bar-container">
                                <div class="bar" style={format!("width: {}%;", bar_width_percent)}>
                                </div>
                            </div>
                        </div>
                    }
                }) }
            </div>
        </div>
    }
}