use std::path::{Path, PathBuf};

use serde::Deserialize;
use serde_json::{Map, Value, json};

use super::{HookFormat, HookInput, HookResponse, InstallOutcome, ParseError, Target, allow_reason};
use crate::verdict::Verdict;

pub struct CodexTarget;

impl Target for CodexTarget {
    fn name(&self) -> &'static str {
        "codex"
    }

    fn display_name(&self) -> &'static str {
        "Codex (OpenAI)"
    }

    fn detect_paths(&self, home: &Path) -> Vec<PathBuf> {
        vec![home.join(".codex")]
    }

    fn install(&self, home: &Path) -> Result<InstallOutcome, String> {
        let dir = home.join(".codex");
        if !dir.exists() {
            return Ok(InstallOutcome::Skipped {
                reason: format!(
                    "~/.codex not found at {} (Codex CLI not installed)",
                    dir.display()
                ),
            });
        }

        let path = dir.join("hooks.json");
        let binary = "safe-chains hook codex";

        if path.exists() {
            let contents = std::fs::read_to_string(&path)
                .map_err(|e| format!("Could not read {}: {e}", path.display()))?;
            let mut settings: Value = serde_json::from_str(&contents)
                .map_err(|e| format!("Could not parse {}: {e}", path.display()))?;

            if has_safe_chains_hook(&settings) {
                return Ok(InstallOutcome::AlreadyConfigured { path });
            }

            add_hook(&mut settings, binary);
            let output = serde_json::to_string_pretty(&settings).expect("serializing valid JSON");
            std::fs::write(&path, format!("{output}\n"))
                .map_err(|e| format!("Could not write {}: {e}", path.display()))?;
            Ok(InstallOutcome::Installed { path })
        } else {
            let mut settings = Value::Object(Map::new());
            add_hook(&mut settings, binary);
            let output = serde_json::to_string_pretty(&settings).expect("serializing valid JSON");
            std::fs::write(&path, format!("{output}\n"))
                .map_err(|e| format!("Could not write {}: {e}", path.display()))?;
            Ok(InstallOutcome::Installed { path })
        }
    }

    fn hook_format(&self) -> Option<&dyn HookFormat> {
        Some(&CodexHookFormat)
    }
}

struct CodexHookFormat;

#[derive(Deserialize)]
struct ToolInput {
    command: String,
}

#[derive(Deserialize)]
struct CodexHookEnvelope {
    tool_input: ToolInput,
    #[serde(default)]
    cwd: Option<String>,
}

impl HookFormat for CodexHookFormat {
    fn parse_input(&self, stdin: &str) -> Result<HookInput, ParseError> {
        let envelope: CodexHookEnvelope = serde_json::from_str(stdin).map_err(|e| ParseError {
            message: e.to_string(),
        })?;
        Ok(HookInput {
            command: envelope.tool_input.command,
            cwd: envelope.cwd,
        })
    }

    fn render_response(&self, verdict: Verdict) -> HookResponse {
        if verdict.is_allowed() {
            let reason = allow_reason(verdict);
            let body = json!({
                "hookSpecificOutput": {
                    "hookEventName": "PreToolUse",
                    "permissionDecision": "allow",
                    "permissionDecisionReason": reason,
                }
            });
            HookResponse {
                stdout: serde_json::to_string(&body).unwrap_or_default(),
                exit_code: 0,
            }
        } else {
            HookResponse {
                stdout: String::new(),
                exit_code: 0,
            }
        }
    }
}

fn hook_entry(binary: &str) -> Value {
    json!({
        "matcher": "Bash",
        "hooks": [{
            "type": "command",
            "command": binary,
        }]
    })
}

fn has_safe_chains_hook(settings: &Value) -> bool {
    settings
        .get("PreToolUse")
        .and_then(|arr| arr.as_array())
        .is_some_and(|entries| {
            entries.iter().any(|entry| {
                entry
                    .get("hooks")
                    .and_then(|h| h.as_array())
                    .is_some_and(|hooks| {
                        hooks.iter().any(|hook| {
                            hook.get("command")
                                .and_then(|c| c.as_str())
                                .is_some_and(|cmd| cmd.contains("safe-chains"))
                        })
                    })
            })
        })
}

fn add_hook(settings: &mut Value, binary: &str) {
    if !settings.is_object() {
        *settings = json!({});
    }
    let Some(obj) = settings.as_object_mut() else {
        unreachable!("settings was just set to an object");
    };
    let pre_tool_use = obj
        .entry("PreToolUse")
        .or_insert_with(|| json!([]))
        .as_array_mut()
        .expect("PreToolUse key was created above as an array");
    pre_tool_use.push(hook_entry(binary));
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::verdict::SafetyLevel;

    fn target() -> CodexTarget {
        CodexTarget
    }

    #[test]
    fn install_no_codex_dir_skips() {
        let dir = tempfile::tempdir().unwrap();
        let outcome = target().install(dir.path()).unwrap();
        assert!(matches!(outcome, InstallOutcome::Skipped { .. }));
    }

    #[test]
    fn install_creates_hooks_file() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::create_dir(dir.path().join(".codex")).unwrap();
        let outcome = target().install(dir.path()).unwrap();
        assert!(matches!(outcome, InstallOutcome::Installed { .. }));
        let contents = std::fs::read_to_string(dir.path().join(".codex/hooks.json")).unwrap();
        let settings: Value = serde_json::from_str(&contents).unwrap();
        assert!(has_safe_chains_hook(&settings));
    }

    #[test]
    fn install_idempotent() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::create_dir(dir.path().join(".codex")).unwrap();
        target().install(dir.path()).unwrap();
        let outcome = target().install(dir.path()).unwrap();
        assert!(matches!(outcome, InstallOutcome::AlreadyConfigured { .. }));
    }

    #[test]
    fn install_uses_subcommand_invocation() {
        // The binary entry must be `safe-chains hook codex`, not just
        // `safe-chains`, so the runtime knows which envelope to emit.
        let dir = tempfile::tempdir().unwrap();
        std::fs::create_dir(dir.path().join(".codex")).unwrap();
        target().install(dir.path()).unwrap();
        let contents = std::fs::read_to_string(dir.path().join(".codex/hooks.json")).unwrap();
        assert!(contents.contains("safe-chains hook codex"));
    }

    #[test]
    fn install_preserves_existing_hooks() {
        let dir = tempfile::tempdir().unwrap();
        let codex_dir = dir.path().join(".codex");
        std::fs::create_dir(&codex_dir).unwrap();
        std::fs::write(
            codex_dir.join("hooks.json"),
            r#"{"PostToolUse": [{"matcher": "Bash", "hooks": [{"type": "command", "command": "log-it"}]}]}"#,
        )
        .unwrap();
        target().install(dir.path()).unwrap();
        let contents = std::fs::read_to_string(codex_dir.join("hooks.json")).unwrap();
        let settings: Value = serde_json::from_str(&contents).unwrap();
        assert!(has_safe_chains_hook(&settings));
        assert!(
            settings.get("PostToolUse").is_some(),
            "existing PostToolUse must be preserved"
        );
    }

    #[test]
    fn parse_input_extracts_command() {
        let stdin = r#"{"tool_name": "Bash", "tool_input": {"command": "ls -la"}}"#;
        let parsed = CodexHookFormat.parse_input(stdin).unwrap();
        assert_eq!(parsed.command, "ls -la");
    }

    #[test]
    fn parse_input_with_optional_cwd() {
        let stdin = r#"{"tool_input": {"command": "pwd"}, "cwd": "/Users/me"}"#;
        let parsed = CodexHookFormat.parse_input(stdin).unwrap();
        assert_eq!(parsed.cwd.as_deref(), Some("/Users/me"));
    }

    #[test]
    fn parse_input_rejects_garbage() {
        assert!(CodexHookFormat.parse_input("not json").is_err());
        assert!(CodexHookFormat.parse_input("{}").is_err());
    }

    #[test]
    fn render_response_allow_emits_allow_envelope() {
        let r = CodexHookFormat.render_response(Verdict::Allowed(SafetyLevel::Inert));
        let v: Value = serde_json::from_str(&r.stdout).unwrap();
        assert_eq!(
            v.pointer("/hookSpecificOutput/permissionDecision")
                .and_then(|d| d.as_str()),
            Some("allow"),
        );
        assert_eq!(
            v.pointer("/hookSpecificOutput/hookEventName")
                .and_then(|d| d.as_str()),
            Some("PreToolUse"),
        );
    }

    #[test]
    fn render_response_deny_emits_empty_body() {
        let r = CodexHookFormat.render_response(Verdict::Denied);
        assert_eq!(r.stdout, "");
    }
}
