//!
//! Objective tool registration backed by Workspace API authority.
//!
//! Objectives are project-level planning context. Runtime Workers may not know
//! local `.yoi/objectives` paths, so model-visible Objective tools go through
//! the scoped Workspace API.

use std::sync::Arc;

use async_trait::async_trait;
use llm_engine::tool::{
    Tool, ToolDefinition, ToolError, ToolExecutionContext, ToolMeta, ToolOutput,
};
use serde::{Deserialize, Serialize};
use serde_json::json;

use crate::worker::{WorkspaceClient, WorkspaceRequest, WorkspaceRequestMethod};

#[derive(Clone, Debug)]
pub struct WorkspaceHttpObjectiveBackend {
    client: Arc<dyn WorkspaceClient>,
}

impl WorkspaceHttpObjectiveBackend {
    pub fn new(client: Arc<dyn WorkspaceClient>) -> Self {
        Self { client }
    }

    async fn list(&self, input: ObjectiveListInput) -> Result<ToolOutput, ToolError> {
        let mut url = format!(
            "/api/w/{}/objectives",
            self.client.workspace_id().unwrap_or_default()
        );
        if let Some(limit) = input.limit {
            url.push_str(&format!("?limit={}", limit.min(1000)));
        }
        let response = get_json::<ObjectiveListResponse>(self.client.as_ref(), &url)
            .await
            .map_err(backend_error)?;
        let count = response.items.len();
        Ok(ToolOutput {
            summary: format!("Listed {count} objective(s)"),
            content: Some(serde_json::to_string_pretty(&response).map_err(decode_error)?),
        })
    }

    async fn show(&self, input: ObjectiveShowInput) -> Result<ToolOutput, ToolError> {
        let id = validate_id(&input.id, "ObjectiveShow")?;
        let url = self.objective_url(id);
        let response = get_json::<ObjectiveDetail>(self.client.as_ref(), &url)
            .await
            .map_err(backend_error)?;
        Ok(objective_output(
            format!("Read objective {}", response.id),
            response,
        )?)
    }

    async fn create(&self, input: ObjectiveCreateInput) -> Result<ToolOutput, ToolError> {
        if input.title.trim().is_empty() {
            return Err(ToolError::InvalidArgument(
                "ObjectiveCreate requires non-empty title".to_string(),
            ));
        }
        let url = format!(
            "/api/w/{}/objectives",
            self.client.workspace_id().unwrap_or_default()
        );
        let response = send_json::<ObjectiveCreateInput, ObjectiveDetail>(
            self.client.as_ref(),
            reqwest::Method::POST,
            &url,
            &input,
        )
        .await
        .map_err(backend_error)?;
        Ok(objective_output(
            format!("Created objective {}", response.id),
            response,
        )?)
    }

    async fn edit(&self, input: ObjectiveEditInput) -> Result<ToolOutput, ToolError> {
        let id = validate_id(&input.id, "ObjectiveEdit")?;
        if input.title.is_none() && input.old_string.is_none() && input.new_string.is_none() {
            return Err(ToolError::InvalidArgument(
                "ObjectiveEdit requires title or old_string/new_string".to_string(),
            ));
        }
        let url = self.objective_url(id);
        let body = ObjectiveEditRequest {
            title: input.title,
            old_string: input.old_string,
            new_string: input.new_string,
            replace_all: input.replace_all,
        };
        let response = send_json::<ObjectiveEditRequest, ObjectiveDetail>(
            self.client.as_ref(),
            reqwest::Method::PATCH,
            &url,
            &body,
        )
        .await
        .map_err(backend_error)?;
        Ok(objective_output(
            format!("Edited objective {}", response.id),
            response,
        )?)
    }

    async fn set_state(&self, input: ObjectiveSetStateInput) -> Result<ToolOutput, ToolError> {
        let id = validate_id(&input.id, "ObjectiveSetState")?;
        if input.state.trim().is_empty() {
            return Err(ToolError::InvalidArgument(
                "ObjectiveSetState requires non-empty state".to_string(),
            ));
        }
        let url = format!("{}/state", self.objective_url(id));
        let response = send_json::<ObjectiveSetStateRequest, ObjectiveDetail>(
            self.client.as_ref(),
            reqwest::Method::POST,
            &url,
            &ObjectiveSetStateRequest { state: input.state },
        )
        .await
        .map_err(backend_error)?;
        Ok(objective_output(
            format!("Updated objective {} state", response.id),
            response,
        )?)
    }

    async fn link_ticket(&self, input: ObjectiveLinkTicketInput) -> Result<ToolOutput, ToolError> {
        let id = validate_id(&input.id, "ObjectiveLinkTicket")?;
        let ticket_id = validate_id(&input.ticket_id, "ObjectiveLinkTicket")?;
        let url = format!("{}/ticket-links", self.objective_url(id));
        let response = send_json::<ObjectiveLinkTicketRequest, ObjectiveDetail>(
            self.client.as_ref(),
            reqwest::Method::POST,
            &url,
            &ObjectiveLinkTicketRequest {
                ticket_id: ticket_id.to_string(),
            },
        )
        .await
        .map_err(backend_error)?;
        Ok(objective_output(
            format!("Linked ticket {ticket_id} to objective {}", response.id),
            response,
        )?)
    }

    async fn unlink_ticket(
        &self,
        input: ObjectiveUnlinkTicketInput,
    ) -> Result<ToolOutput, ToolError> {
        let id = validate_id(&input.id, "ObjectiveUnlinkTicket")?;
        let ticket_id = validate_id(&input.ticket_id, "ObjectiveUnlinkTicket")?;
        let url = format!("{}/ticket-links/{}", self.objective_url(id), ticket_id);
        let response = delete_json::<ObjectiveDetail>(self.client.as_ref(), &url)
            .await
            .map_err(backend_error)?;
        Ok(objective_output(
            format!("Unlinked ticket {ticket_id} from objective {}", response.id),
            response,
        )?)
    }

    fn objective_url(&self, id: &str) -> String {
        let workspace_id = self.client.workspace_id().unwrap_or_default();
        format!("/api/w/{workspace_id}/objectives/{id}")
    }
}

#[derive(Debug, thiserror::Error)]
pub enum WorkspaceObjectiveBackendError {
    #[error("workspace objective backend request failed: {0}")]
    Request(#[from] crate::worker::WorkspaceClientError),
    #[error("workspace objective backend returned HTTP {status}: {body}")]
    Http {
        status: reqwest::StatusCode,
        body: String,
    },
    #[error("decode objective backend response: {0}")]
    Decode(#[from] serde_json::Error),
}

fn decode_error(error: serde_json::Error) -> ToolError {
    ToolError::ExecutionFailed(format!("decode objective backend response: {error}"))
}

fn backend_error(error: WorkspaceObjectiveBackendError) -> ToolError {
    ToolError::ExecutionFailed(error.to_string())
}

async fn get_json<T: for<'de> Deserialize<'de>>(
    client: &dyn WorkspaceClient,
    path: &str,
) -> Result<T, WorkspaceObjectiveBackendError> {
    decode_response(client.execute(WorkspaceRequest::get(path))?)
}

async fn send_json<B: Serialize, T: for<'de> Deserialize<'de>>(
    client: &dyn WorkspaceClient,
    method: reqwest::Method,
    path: &str,
    body: &B,
) -> Result<T, WorkspaceObjectiveBackendError> {
    let method = match method {
        reqwest::Method::POST => WorkspaceRequestMethod::Post,
        reqwest::Method::PUT => WorkspaceRequestMethod::Put,
        reqwest::Method::PATCH => WorkspaceRequestMethod::Patch,
        reqwest::Method::DELETE => WorkspaceRequestMethod::Delete,
        _ => WorkspaceRequestMethod::Get,
    };
    decode_response(client.execute(WorkspaceRequest::json(
        method,
        path,
        serde_json::to_string(body)?,
    ))?)
}

async fn delete_json<T: for<'de> Deserialize<'de>>(
    client: &dyn WorkspaceClient,
    path: &str,
) -> Result<T, WorkspaceObjectiveBackendError> {
    decode_response(client.execute(WorkspaceRequest {
        method: WorkspaceRequestMethod::Delete,
        path: path.to_string(),
        body: None,
    })?)
}

fn decode_response<T: for<'de> Deserialize<'de>>(
    response: crate::worker::WorkspaceResponse,
) -> Result<T, WorkspaceObjectiveBackendError> {
    let status = reqwest::StatusCode::from_u16(response.status)
        .unwrap_or(reqwest::StatusCode::INTERNAL_SERVER_ERROR);
    if !response.is_success() {
        return Err(WorkspaceObjectiveBackendError::Http {
            status,
            body: response.body,
        });
    }
    serde_json::from_str(&response.body).map_err(Into::into)
}

fn objective_output(summary: String, response: ObjectiveDetail) -> Result<ToolOutput, ToolError> {
    Ok(ToolOutput {
        summary,
        content: Some(serde_json::to_string_pretty(&response).map_err(decode_error)?),
    })
}

fn validate_id<'a>(id: &'a str, tool_name: &str) -> Result<&'a str, ToolError> {
    let id = id.trim();
    if id.is_empty() || id.contains('/') {
        return Err(ToolError::InvalidArgument(format!(
            "{tool_name} requires non-empty canonical id without '/'"
        )));
    }
    Ok(id)
}

pub fn workspace_http_objective_tools(client: Arc<dyn WorkspaceClient>) -> Vec<ToolDefinition> {
    let backend = WorkspaceHttpObjectiveBackend::new(client);
    vec![
        objective_tool(
            "ObjectiveList",
            LIST_DESCRIPTION,
            list_schema(),
            backend.clone(),
            ObjectiveOperation::List,
        ),
        objective_tool(
            "ObjectiveShow",
            SHOW_DESCRIPTION,
            show_schema(),
            backend.clone(),
            ObjectiveOperation::Show,
        ),
        objective_tool(
            "ObjectiveCreate",
            CREATE_DESCRIPTION,
            create_schema(),
            backend.clone(),
            ObjectiveOperation::Create,
        ),
        objective_tool(
            "ObjectiveEdit",
            EDIT_DESCRIPTION,
            edit_schema(),
            backend.clone(),
            ObjectiveOperation::Edit,
        ),
        objective_tool(
            "ObjectiveSetState",
            SET_STATE_DESCRIPTION,
            set_state_schema(),
            backend.clone(),
            ObjectiveOperation::SetState,
        ),
        objective_tool(
            "ObjectiveLinkTicket",
            LINK_TICKET_DESCRIPTION,
            link_ticket_schema(),
            backend.clone(),
            ObjectiveOperation::LinkTicket,
        ),
        objective_tool(
            "ObjectiveUnlinkTicket",
            UNLINK_TICKET_DESCRIPTION,
            unlink_ticket_schema(),
            backend,
            ObjectiveOperation::UnlinkTicket,
        ),
    ]
}

#[derive(Clone, Copy)]
enum ObjectiveOperation {
    List,
    Show,
    Create,
    Edit,
    SetState,
    LinkTicket,
    UnlinkTicket,
}

fn objective_tool(
    name: &'static str,
    description: &'static str,
    schema: serde_json::Value,
    backend: WorkspaceHttpObjectiveBackend,
    operation: ObjectiveOperation,
) -> ToolDefinition {
    Arc::new(move || {
        (
            ToolMeta::new(name)
                .description(description)
                .input_schema(schema.clone()),
            Arc::new(WorkspaceHttpObjectiveTool {
                backend: backend.clone(),
                operation,
            }) as Arc<dyn Tool>,
        )
    })
}

#[derive(Clone)]
struct WorkspaceHttpObjectiveTool {
    backend: WorkspaceHttpObjectiveBackend,
    operation: ObjectiveOperation,
}

#[async_trait]
impl Tool for WorkspaceHttpObjectiveTool {
    async fn execute(
        &self,
        input_json: &str,
        _ctx: ToolExecutionContext,
    ) -> Result<ToolOutput, ToolError> {
        match self.operation {
            ObjectiveOperation::List => {
                let input = parse_input::<ObjectiveListInput>(input_json)?;
                self.backend.list(input).await
            }
            ObjectiveOperation::Show => {
                let input = parse_input::<ObjectiveShowInput>(input_json)?;
                self.backend.show(input).await
            }
            ObjectiveOperation::Create => {
                let input = parse_input::<ObjectiveCreateInput>(input_json)?;
                self.backend.create(input).await
            }
            ObjectiveOperation::Edit => {
                let input = parse_input::<ObjectiveEditInput>(input_json)?;
                self.backend.edit(input).await
            }
            ObjectiveOperation::SetState => {
                let input = parse_input::<ObjectiveSetStateInput>(input_json)?;
                self.backend.set_state(input).await
            }
            ObjectiveOperation::LinkTicket => {
                let input = parse_input::<ObjectiveLinkTicketInput>(input_json)?;
                self.backend.link_ticket(input).await
            }
            ObjectiveOperation::UnlinkTicket => {
                let input = parse_input::<ObjectiveUnlinkTicketInput>(input_json)?;
                self.backend.unlink_ticket(input).await
            }
        }
    }
}

fn parse_input<T: for<'de> Deserialize<'de>>(input: &str) -> Result<T, ToolError> {
    serde_json::from_str(input).map_err(|error| ToolError::InvalidArgument(error.to_string()))
}

const LIST_DESCRIPTION: &str =
    "List Objective records through Backend Workspace API authority as bounded summaries.";
const SHOW_DESCRIPTION: &str =
    "Show one Objective record by canonical id through Backend Workspace API authority.";
const CREATE_DESCRIPTION: &str =
    "Create an Objective record through Backend Workspace API authority.";
const EDIT_DESCRIPTION: &str =
    "Partially edit an Objective title and/or body through Backend Workspace API authority.";
const SET_STATE_DESCRIPTION: &str =
    "Set an Objective state through Backend Workspace API authority.";
const LINK_TICKET_DESCRIPTION: &str =
    "Link a Ticket id to an Objective through Backend Workspace API authority.";
const UNLINK_TICKET_DESCRIPTION: &str =
    "Unlink a Ticket id from an Objective through Backend Workspace API authority.";

fn list_schema() -> serde_json::Value {
    json!({
        "type":"object",
        "additionalProperties": false,
        "properties":{
            "limit":{"type":["integer","null"],"minimum":0,"maximum":1000}
        }
    })
}

fn show_schema() -> serde_json::Value {
    id_schema(&["id"])
}

fn create_schema() -> serde_json::Value {
    json!({
        "type":"object",
        "additionalProperties": false,
        "required":["title"],
        "properties":{
            "title":{"type":"string","minLength":1},
            "body_md":{"type":"string"},
            "state":{"type":"string","default":"active"},
            "linked_tickets":{"type":"array","items":{"type":"string"}}
        }
    })
}

fn edit_schema() -> serde_json::Value {
    json!({
        "type":"object",
        "additionalProperties": false,
        "required":["id"],
        "properties":{
            "id":{"type":"string"},
            "title":{"type":["string","null"]},
            "old_string":{"type":["string","null"]},
            "new_string":{"type":["string","null"]},
            "replace_all":{"type":"boolean","default":false}
        }
    })
}

fn set_state_schema() -> serde_json::Value {
    json!({
        "type":"object",
        "additionalProperties": false,
        "required":["id","state"],
        "properties":{
            "id":{"type":"string"},
            "state":{"type":"string","minLength":1}
        }
    })
}

fn link_ticket_schema() -> serde_json::Value {
    id_ticket_schema(&["id", "ticket_id"])
}

fn unlink_ticket_schema() -> serde_json::Value {
    id_ticket_schema(&["id", "ticket_id"])
}

fn id_schema(required: &[&str]) -> serde_json::Value {
    json!({
        "type":"object",
        "additionalProperties": false,
        "required": required,
        "properties":{
            "id":{"type":"string"}
        }
    })
}

fn id_ticket_schema(required: &[&str]) -> serde_json::Value {
    json!({
        "type":"object",
        "additionalProperties": false,
        "required": required,
        "properties":{
            "id":{"type":"string"},
            "ticket_id":{"type":"string"}
        }
    })
}

#[derive(Debug, Deserialize)]
struct ObjectiveListInput {
    limit: Option<usize>,
}

#[derive(Debug, Deserialize)]
struct ObjectiveShowInput {
    id: String,
}

#[derive(Debug, Serialize, Deserialize)]
struct ObjectiveCreateInput {
    title: String,
    #[serde(default)]
    body_md: String,
    #[serde(default = "default_state")]
    state: String,
    #[serde(default)]
    linked_tickets: Vec<String>,
}

#[derive(Debug, Deserialize)]
struct ObjectiveEditInput {
    id: String,
    title: Option<String>,
    old_string: Option<String>,
    new_string: Option<String>,
    #[serde(default)]
    replace_all: bool,
}

#[derive(Debug, Serialize)]
struct ObjectiveEditRequest {
    title: Option<String>,
    old_string: Option<String>,
    new_string: Option<String>,
    replace_all: bool,
}

#[derive(Debug, Deserialize)]
struct ObjectiveSetStateInput {
    id: String,
    state: String,
}

#[derive(Debug, Serialize)]
struct ObjectiveSetStateRequest {
    state: String,
}

#[derive(Debug, Deserialize)]
struct ObjectiveLinkTicketInput {
    id: String,
    ticket_id: String,
}

#[derive(Debug, Deserialize)]
struct ObjectiveUnlinkTicketInput {
    id: String,
    ticket_id: String,
}

#[derive(Debug, Serialize)]
struct ObjectiveLinkTicketRequest {
    ticket_id: String,
}

fn default_state() -> String {
    "active".to_string()
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
struct ObjectiveListResponse {
    items: Vec<ObjectiveSummary>,
    invalid_records: Vec<InvalidProjectRecord>,
    record_authority: String,
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
struct InvalidProjectRecord {
    label: String,
    reason: String,
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
struct ObjectiveSummary {
    id: String,
    title: String,
    state: String,
    updated_at: Option<String>,
    summary: String,
    linked_tickets: Vec<String>,
    record_source: String,
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
struct ObjectiveDetail {
    id: String,
    title: String,
    state: String,
    created_at: Option<String>,
    updated_at: Option<String>,
    linked_tickets: Vec<String>,
    body: String,
    body_truncated: bool,
    record_source: String,
}

#[cfg(test)]
mod tests {
    use super::*;
    use llm_engine::tool::ToolDefinition;

    fn tool_names(definitions: Vec<ToolDefinition>) -> Vec<String> {
        let mut names = definitions
            .into_iter()
            .map(|tool| tool().0.name)
            .collect::<Vec<_>>();
        names.sort();
        names
    }

    #[test]
    fn workspace_http_objective_tools_include_objective_crud_tools() {
        let names = tool_names(workspace_http_objective_tools(Arc::new(
            crate::worker::RuntimeWorkspaceHttpClient::new(
                "workspace",
                "http://backend",
                "test-worker",
            ),
        )));

        assert_eq!(
            names,
            vec![
                "ObjectiveCreate",
                "ObjectiveEdit",
                "ObjectiveLinkTicket",
                "ObjectiveList",
                "ObjectiveSetState",
                "ObjectiveShow",
                "ObjectiveUnlinkTicket",
            ]
        );
    }

    #[test]
    fn objective_tool_schemas_are_bounded_and_mutation_scoped() {
        let list = list_schema();
        assert_eq!(list["properties"]["limit"]["maximum"], 1000);
        let show = show_schema();
        assert_eq!(show["required"][0], "id");
        let create = create_schema();
        assert_eq!(create["required"][0], "title");
        let edit = edit_schema();
        assert_eq!(edit["required"][0], "id");
        let link = link_ticket_schema();
        assert_eq!(link["required"], json!(["id", "ticket_id"]));
    }
}