// DCR — Cargo-like C/C++ project manager.
//
// Copyright (C) 2026 Dexoron (Bezotechestvo Vladimir) <main@dexoron.su>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

use crate::core::build_config::Config;
use crate::utils::build::normalize_target_os;
use std::collections::{HashMap, HashSet};
use std::path::{Path, PathBuf};
use toml::Value;

/// Represents a member of the workspace.
#[derive(Debug, Clone)]
pub struct WorkspaceMember {
    pub name: String,
    pub path: PathBuf,
    pub deps: Vec<String>,
    pub main: bool,
}

/// Represents the workspace as a collection of members.
#[derive(Debug, Clone)]
pub struct Workspace {
    pub members: Vec<WorkspaceMember>,
}

impl Workspace {
    /// Returns the main workspace member, preferring the one with `main: true` or the first member.
    pub fn main_member(&self) -> Option<&WorkspaceMember> {
        self.members
            .iter()
            .find(|m| m.main)
            .or_else(|| self.members.first())
    }
}

/// Parses the workspace configuration from the TOML config.
///
/// # Parameters
/// - `config`: Root `dcr.toml` (may be workspace-only or mixed).
/// - `profile` / `target`: Select profile- and target-specific `[workspace.*]` tables.
/// - `root`: Workspace root used to resolve member paths.
///
/// # Returns
/// - `Ok(None)` if no workspace table applies.
/// - `Ok(Some(Workspace))` with members (and optional main).
/// - `Err` on invalid member paths or config shape.
pub fn parse_workspace(
    config: &Config,
    profile: &str,
    target: Option<&str>,
    root: &Path,
) -> Result<Option<Workspace>, String> {
    let mut table = None;
    // Create ordered list of possible config keys for lookup
    let combinations = if let Some(t) = target {
        let normalized_t = normalize_target_os(t);
        vec![
            format!("workspace.{}.{}", normalized_t, profile),
            format!("workspace.{}.{}", profile, normalized_t),
            format!("workspace.{}", normalized_t),
            format!("workspace.{}", profile),
            "workspace".to_string(),
        ]
    } else {
        vec![format!("workspace.{}", profile), "workspace".to_string()]
    };
    for key in combinations {
        if let Some(val) = config.get(&key).and_then(|v| v.as_table()) {
            table = Some(val);
            break;
        }
    }
    let table = match table {
        Some(t) => t,
        None => return Ok(None),
    };

    let mut members = Vec::new();
    for (name, value) in table {
        let tbl = value
            .as_table()
            .ok_or_else(|| format!("workspace.{name} must be a table with path and deps"))?;
        let path_raw = tbl
            .get("path")
            .and_then(|v| v.as_str())
            .ok_or_else(|| format!("workspace.{name}.path is required"))?;
        let path = resolve_path(root, path_raw)?;
        if !path.join("dcr.toml").is_file() {
            return Err(format!(
                "workspace.{name}.path does not contain dcr.toml: {}",
                path.display()
            ));
        }
        let deps = parse_deps(tbl.get("deps"))?;
        members.push(WorkspaceMember {
            name: name.to_string(),
            path,
            deps,
            main: tbl.get("main").and_then(|v| v.as_bool()).unwrap_or(false),
        });
    }

    let mut ws = Workspace { members };
    ws.members = topo_sort(&ws.members)?;
    Ok(Some(ws))
}

/// Resolves a path, making it absolute if relative to root.
fn resolve_path(root: &Path, raw: &str) -> Result<PathBuf, String> {
    let p = Path::new(raw);
    let full = if p.is_absolute() {
        p.to_path_buf()
    } else {
        root.join(p)
    };
    Ok(full)
}

/// Parses dependencies list from TOML value into Vec<String>.
fn parse_deps(value: Option<&Value>) -> Result<Vec<String>, String> {
    let Some(value) = value else {
        return Ok(Vec::new());
    };
    let arr = value
        .as_array()
        .ok_or_else(|| "workspace deps must be an array of strings".to_string())?;
    let mut out = Vec::new();
    for item in arr {
        let s = item
            .as_str()
            .ok_or_else(|| "workspace deps must be an array of strings".to_string())?;
        out.push(s.to_string());
    }
    Ok(out)
}

/// Performs a topological sort on members to handle dependencies and detect cycles.
fn topo_sort(members: &[WorkspaceMember]) -> Result<Vec<WorkspaceMember>, String> {
    let mut map = HashMap::new();
    for m in members {
        map.insert(m.name.clone(), m.clone());
    }
    let mut state: HashMap<String, u8> = HashMap::new();
    // Use 0=unvisited, 1=visiting, 2=visited for cycle detection
    let mut order: Vec<WorkspaceMember> = Vec::new();

    for name in map.keys() {
        if *state.get(name).unwrap_or(&0) == 0 {
            visit(name, &map, &mut state, &mut order)?;
        }
    }
    Ok(order)
}

/// Recursive function for DFS-based topological sort with cycle detection.
fn visit(
    name: &str,
    map: &HashMap<String, WorkspaceMember>,
    state: &mut HashMap<String, u8>,
    order: &mut Vec<WorkspaceMember>,
) -> Result<(), String> {
    // Check current visit state to detect cycles
    match state.get(name).copied().unwrap_or(0) {
        1 => return Err(format!("workspace dependency cycle at {name}")),
        2 => return Ok(()),
        _ => {}
    }
    state.insert(name.to_string(), 1);
    let member = map
        .get(name)
        .ok_or_else(|| format!("unknown workspace member {name}"))?;
    let mut seen = HashSet::new();
    for dep in &member.deps {
        if !seen.insert(dep) {
            continue;
        }
        if !map.contains_key(dep) {
            return Err(format!("workspace dependency '{dep}' not found"));
        }
        visit(dep, map, state, order)?;
    }
    state.insert(name.to_string(), 2);
    order.push(member.clone());
    Ok(())
}